shared_source/c_tcl_base_7_5_w_mods/tclwinsock.c

/* $Header$ */
/* 
 * tclWinSock.c --
 *
 *      This file contains Windows-specific socket related code.
 *
 * Copyright (c) 1995-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution
 * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclwinsock.c,v 1.1.1.1 2001/06/13 04:50:36 dtashley Exp $
 */

#include "tclWinInt.h"

/*
 * The following variable is used to tell whether this module has been
 * initialized.
 */

static int initialized = 0;

static int  hostnameInitialized = 0;
static char hostname[255];      /* This buffer should be big enough for
                                 * hostname plus domain name. */

TCL_DECLARE_MUTEX(socketMutex)

/*
 * The following structure contains pointers to all of the WinSock API entry
 * points used by Tcl.  It is initialized by InitSockets.  Since we
 * dynamically load Winsock.dll on demand, we must use this function table
 * to refer to functions in the socket API.
 */

static struct {
    HINSTANCE hInstance;        /* Handle to WinSock library. */
    SOCKET (PASCAL FAR *accept)(SOCKET s, struct sockaddr FAR *addr,
            int FAR *addrlen);
    int (PASCAL FAR *bind)(SOCKET s, const struct sockaddr FAR *addr,
            int namelen);
    int (PASCAL FAR *closesocket)(SOCKET s);
    int (PASCAL FAR *connect)(SOCKET s, const struct sockaddr FAR *name,
            int namelen);
    int (PASCAL FAR *ioctlsocket)(SOCKET s, long cmd, u_long FAR *argp);
    int (PASCAL FAR *getsockopt)(SOCKET s, int level, int optname,
            char FAR * optval, int FAR *optlen);
    u_short (PASCAL FAR *htons)(u_short hostshort);
    unsigned long (PASCAL FAR *inet_addr)(const char FAR * cp);
    char FAR * (PASCAL FAR *inet_ntoa)(struct in_addr in);
    int (PASCAL FAR *listen)(SOCKET s, int backlog);
    u_short (PASCAL FAR *ntohs)(u_short netshort);
    int (PASCAL FAR *recv)(SOCKET s, char FAR * buf, int len, int flags);
    int (PASCAL FAR *select)(int nfds, fd_set FAR * readfds,
            fd_set FAR * writefds, fd_set FAR * exceptfds,
            const struct timeval FAR * tiemout);
    int (PASCAL FAR *send)(SOCKET s, const char FAR * buf, int len, int flags);
    int (PASCAL FAR *setsockopt)(SOCKET s, int level, int optname,
            const char FAR * optval, int optlen);
    int (PASCAL FAR *shutdown)(SOCKET s, int how);
    SOCKET (PASCAL FAR *socket)(int af, int type, int protocol);
    struct hostent FAR * (PASCAL FAR *gethostbyname)(const char FAR * name);
    struct hostent FAR * (PASCAL FAR *gethostbyaddr)(const char FAR *addr,
            int addrlen, int addrtype);
    int (PASCAL FAR *gethostname)(char FAR * name, int namelen);
    int (PASCAL FAR *getpeername)(SOCKET sock, struct sockaddr FAR *name,
            int FAR *namelen);
    struct servent FAR * (PASCAL FAR *getservbyname)(const char FAR * name,
            const char FAR * proto);
    int (PASCAL FAR *getsockname)(SOCKET sock, struct sockaddr FAR *name,
            int FAR *namelen);
    int (PASCAL FAR *WSAStartup)(WORD wVersionRequired, LPWSADATA lpWSAData);
    int (PASCAL FAR *WSACleanup)(void);
    int (PASCAL FAR *WSAGetLastError)(void);
    int (PASCAL FAR *WSAAsyncSelect)(SOCKET s, HWND hWnd, u_int wMsg,
            long lEvent);
} winSock;

/*
 * The following defines declare the messages used on socket windows.
 */

#define SOCKET_MESSAGE  WM_USER+1
#define SOCKET_SELECT   WM_USER+2
#define SOCKET_TERMINATE WM_USER+3
#define SELECT          TRUE
#define UNSELECT        FALSE

/*
 * The following structure is used to store the data associated with
 * each socket.
 */

typedef struct SocketInfo {
    Tcl_Channel channel;           /* Channel associated with this socket. */
    SOCKET socket;                 /* Windows SOCKET handle. */
    int flags;                     /* Bit field comprised of the flags
                                    * described below.  */
    int watchEvents;               /* OR'ed combination of FD_READ, FD_WRITE,
                                    * FD_CLOSE, FD_ACCEPT and FD_CONNECT that
                                    * indicate which events are interesting. */
    int readyEvents;               /* OR'ed combination of FD_READ, FD_WRITE,
                                    * FD_CLOSE, FD_ACCEPT and FD_CONNECT that
                                    * indicate which events have occurred. */
    int selectEvents;              /* OR'ed combination of FD_READ, FD_WRITE,
                                    * FD_CLOSE, FD_ACCEPT and FD_CONNECT that
                                    * indicate which events are currently
                                    * being selected. */
    int acceptEventCount;          /* Count of the current number of FD_ACCEPTs
                                    * that have arrived and not processed. */
    Tcl_TcpAcceptProc *acceptProc; /* Proc to call on accept. */
    ClientData acceptProcData;     /* The data for the accept proc. */
    int lastError;                 /* Error code from last message. */
    struct SocketInfo *nextPtr;    /* The next socket on the global socket
                                    * list. */
} SocketInfo;

/*
 * The following structure is what is added to the Tcl event queue when
 * a socket event occurs.
 */

typedef struct SocketEvent {
    Tcl_Event header;           /* Information that is standard for
                                 * all events. */
    SOCKET socket;              /* Socket descriptor that is ready.  Used
                                 * to find the SocketInfo structure for
                                 * the file (can't point directly to the
                                 * SocketInfo structure because it could
                                 * go away while the event is queued). */
} SocketEvent;

/*
 * This defines the minimum buffersize maintained by the kernel.
 */

#define TCP_BUFFER_SIZE 4096

/*
 * The following macros may be used to set the flags field of
 * a SocketInfo structure.
 */

#define SOCKET_ASYNC            (1<<0)  /* The socket is in blocking mode. */
#define SOCKET_EOF              (1<<1)  /* A zero read happened on
                                         * the socket. */
#define SOCKET_ASYNC_CONNECT    (1<<2)  /* This socket uses async connect. */
#define SOCKET_PENDING          (1<<3)  /* A message has been sent
                                         * for this socket */

typedef struct ThreadSpecificData {
    /*
     * Every open socket has an entry on the following list.
     */
    
    HWND hwnd;              /* Handle to window for socket messages. */
    HANDLE socketThread;    /* Thread handling the window */
    Tcl_ThreadId threadId;  /* Parent thread. */
    HANDLE readyEvent;      /* Event indicating that a socket event is ready.
                             * Also used to indicate that the socketThread has
                             * been initialized and has started. */
    HANDLE socketListLock;  /* Win32 Event to lock the socketList */
    SocketInfo *socketList;
} ThreadSpecificData;

static Tcl_ThreadDataKey dataKey;
static WNDCLASSA windowClass;

/*
 * Static functions defined in this file.
 */

static SocketInfo *     CreateSocket _ANSI_ARGS_((Tcl_Interp *interp,
                            int port, char *host, int server, char *myaddr,
                            int myport, int async));
static int              CreateSocketAddress _ANSI_ARGS_(
                            (struct sockaddr_in *sockaddrPtr,
                            char *host, int port));
static void             InitSockets _ANSI_ARGS_((void));
static SocketInfo *     NewSocketInfo _ANSI_ARGS_((SOCKET socket));
static void             SocketCheckProc _ANSI_ARGS_((ClientData clientData,
                            int flags));
static int              SocketEventProc _ANSI_ARGS_((Tcl_Event *evPtr,
                            int flags));
static void             SocketExitHandler _ANSI_ARGS_((ClientData clientData));
static LRESULT CALLBACK SocketProc _ANSI_ARGS_((HWND hwnd, UINT message,
                            WPARAM wParam, LPARAM lParam));
static void             SocketSetupProc _ANSI_ARGS_((ClientData clientData,
                            int flags));
static void             SocketThreadExitHandler _ANSI_ARGS_((ClientData clientData));
static int              SocketsEnabled _ANSI_ARGS_((void));
static void             TcpAccept _ANSI_ARGS_((SocketInfo *infoPtr));
static int              TcpBlockProc _ANSI_ARGS_((ClientData instanceData,
                            int mode));
static int              TcpCloseProc _ANSI_ARGS_((ClientData instanceData,
                            Tcl_Interp *interp));
static int              TcpGetOptionProc _ANSI_ARGS_((ClientData instanceData,
                            Tcl_Interp *interp, char *optionName,
                            Tcl_DString *optionValue));
static int              TcpInputProc _ANSI_ARGS_((ClientData instanceData,
                            char *buf, int toRead, int *errorCode));
static int              TcpOutputProc _ANSI_ARGS_((ClientData instanceData,
                            char *buf, int toWrite, int *errorCode));
static void             TcpWatchProc _ANSI_ARGS_((ClientData instanceData,
                            int mask));
static int              TcpGetHandleProc _ANSI_ARGS_((ClientData instanceData,
                            int direction, ClientData *handlePtr));
static int              WaitForSocketEvent _ANSI_ARGS_((SocketInfo *infoPtr,
                            int events, int *errorCodePtr));
static DWORD WINAPI     SocketThread _ANSI_ARGS_((LPVOID arg));

/*
 * This structure describes the channel type structure for TCP socket
 * based IO.
 */

static Tcl_ChannelType tcpChannelType = {
    "tcp",              /* Type name. */
    TcpBlockProc,       /* Set socket into blocking/non-blocking mode. */
    TcpCloseProc,       /* Close proc. */
    TcpInputProc,       /* Input proc. */
    TcpOutputProc,      /* Output proc. */
    NULL,               /* Seek proc. */
    NULL,               /* Set option proc. */
    TcpGetOptionProc,   /* Get option proc. */
    TcpWatchProc,       /* Initialize notifier to watch this channel. */
    TcpGetHandleProc,   /* Get an OS handle from channel. */
};

/*
 * Define version of Winsock required by Tcl.
 */

#define WSA_VERSION_REQD MAKEWORD(1,1)

/*
 *----------------------------------------------------------------------
 *
 * InitSockets --
 *
 *      Initialize the socket module.  Attempts to load the wsock32.dll
 *      library and set up the winSock function table.  If successful,
 *      registers the event window for the socket notifier code.
 *
 *      Assumes Mutex is held.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Dynamically loads wsock32.dll, and registers a new window
 *      class and creates a window for use in asynchronous socket
 *      notification.
 *
 *----------------------------------------------------------------------
 */

static void
InitSockets()
{
    DWORD id;
    WSADATA wsaData;
    ThreadSpecificData *tsdPtr = 
        (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);

    if (! initialized) {
        initialized = 1;
        Tcl_CreateExitHandler(SocketExitHandler, (ClientData) NULL);

        winSock.hInstance = LoadLibraryA("wsock32.dll");

        /*
         * Initialize the function table.
         */

        if (!SocketsEnabled()) {
            return;
        }
    
        winSock.accept = (SOCKET (PASCAL FAR *)(SOCKET s,
                struct sockaddr FAR *addr, int FAR *addrlen))
            GetProcAddress(winSock.hInstance, "accept");
        winSock.bind = (int (PASCAL FAR *)(SOCKET s,
                const struct sockaddr FAR *addr, int namelen))
            GetProcAddress(winSock.hInstance, "bind");
        winSock.closesocket = (int (PASCAL FAR *)(SOCKET s))
            GetProcAddress(winSock.hInstance, "closesocket");
        winSock.connect = (int (PASCAL FAR *)(SOCKET s,
                const struct sockaddr FAR *name, int namelen))
            GetProcAddress(winSock.hInstance, "connect");
        winSock.ioctlsocket = (int (PASCAL FAR *)(SOCKET s, long cmd,
                u_long FAR *argp))
            GetProcAddress(winSock.hInstance, "ioctlsocket");
        winSock.getsockopt = (int (PASCAL FAR *)(SOCKET s,
                int level, int optname, char FAR * optval, int FAR *optlen))
            GetProcAddress(winSock.hInstance, "getsockopt");
        winSock.htons = (u_short (PASCAL FAR *)(u_short hostshort))
            GetProcAddress(winSock.hInstance, "htons");
        winSock.inet_addr = (unsigned long (PASCAL FAR *)(const char FAR *cp))
            GetProcAddress(winSock.hInstance, "inet_addr");
        winSock.inet_ntoa = (char FAR * (PASCAL FAR *)(struct in_addr in))
            GetProcAddress(winSock.hInstance, "inet_ntoa");
        winSock.listen = (int (PASCAL FAR *)(SOCKET s, int backlog))
            GetProcAddress(winSock.hInstance, "listen");
        winSock.ntohs = (u_short (PASCAL FAR *)(u_short netshort))
            GetProcAddress(winSock.hInstance, "ntohs");
        winSock.recv = (int (PASCAL FAR *)(SOCKET s, char FAR * buf,
                int len, int flags)) GetProcAddress(winSock.hInstance, "recv");
        winSock.select = (int (PASCAL FAR *)(int nfds, fd_set FAR * readfds,
                fd_set FAR * writefds, fd_set FAR * exceptfds,
                const struct timeval FAR * tiemout))
            GetProcAddress(winSock.hInstance, "select");
        winSock.send = (int (PASCAL FAR *)(SOCKET s, const char FAR * buf,
                int len, int flags)) GetProcAddress(winSock.hInstance, "send");
        winSock.setsockopt = (int (PASCAL FAR *)(SOCKET s, int level,
                int optname, const char FAR * optval, int optlen))
            GetProcAddress(winSock.hInstance, "setsockopt");
        winSock.shutdown = (int (PASCAL FAR *)(SOCKET s, int how))
            GetProcAddress(winSock.hInstance, "shutdown");
        winSock.socket = (SOCKET (PASCAL FAR *)(int af, int type,
                int protocol)) GetProcAddress(winSock.hInstance, "socket");
        winSock.gethostbyaddr = (struct hostent FAR * (PASCAL FAR *)
                (const char FAR *addr, int addrlen, int addrtype))
            GetProcAddress(winSock.hInstance, "gethostbyaddr");
        winSock.gethostbyname = (struct hostent FAR * (PASCAL FAR *)
                (const char FAR *name))
            GetProcAddress(winSock.hInstance, "gethostbyname");
        winSock.gethostname = (int (PASCAL FAR *)(char FAR * name,
                int namelen)) GetProcAddress(winSock.hInstance, "gethostname");
        winSock.getpeername = (int (PASCAL FAR *)(SOCKET sock,
                struct sockaddr FAR *name, int FAR *namelen))
            GetProcAddress(winSock.hInstance, "getpeername");
        winSock.getservbyname = (struct servent FAR * (PASCAL FAR *)
                (const char FAR * name, const char FAR * proto))
            GetProcAddress(winSock.hInstance, "getservbyname");
        winSock.getsockname = (int (PASCAL FAR *)(SOCKET sock,
                struct sockaddr FAR *name, int FAR *namelen))
            GetProcAddress(winSock.hInstance, "getsockname");
        winSock.WSAStartup = (int (PASCAL FAR *)(WORD wVersionRequired,
                LPWSADATA lpWSAData)) GetProcAddress(winSock.hInstance, "WSAStartup");
        winSock.WSACleanup = (int (PASCAL FAR *)(void))
            GetProcAddress(winSock.hInstance, "WSACleanup");
        winSock.WSAGetLastError = (int (PASCAL FAR *)(void))
            GetProcAddress(winSock.hInstance, "WSAGetLastError");
        winSock.WSAAsyncSelect = (int (PASCAL FAR *)(SOCKET s, HWND hWnd,
                u_int wMsg, long lEvent))
            GetProcAddress(winSock.hInstance, "WSAAsyncSelect");
    
        /*
         * Now check that all fields are properly initialized. If not, return
         * zero to indicate that we failed to initialize properly.
         */
    
        if ((winSock.hInstance == NULL) ||
                (winSock.accept == NULL) ||
                (winSock.bind == NULL) ||
                (winSock.closesocket == NULL) ||
                (winSock.connect == NULL) ||
                (winSock.ioctlsocket == NULL) ||
                (winSock.getsockopt == NULL) ||
                (winSock.htons == NULL) ||
                (winSock.inet_addr == NULL) ||
                (winSock.inet_ntoa == NULL) ||
                (winSock.listen == NULL) ||
                (winSock.ntohs == NULL) ||
                (winSock.recv == NULL) ||
                (winSock.select == NULL) ||
                (winSock.send == NULL) ||
                (winSock.setsockopt == NULL) ||
                (winSock.socket == NULL) ||
                (winSock.gethostbyname == NULL) ||
                (winSock.gethostbyaddr == NULL) ||
                (winSock.gethostname == NULL) ||
                (winSock.getpeername == NULL) ||
                (winSock.getservbyname == NULL) ||
                (winSock.getsockname == NULL) ||
                (winSock.WSAStartup == NULL) ||
                (winSock.WSACleanup == NULL) ||
                (winSock.WSAGetLastError == NULL) ||
                (winSock.WSAAsyncSelect == NULL)) {
            goto unloadLibrary;
        }
        
        /*
         * Create the async notification window with a new class.  We
         * must create a new class to avoid a Windows 95 bug that causes
         * us to get the wrong message number for socket events if the
         * message window is a subclass of a static control.
         */
    
        windowClass.style = 0;
        windowClass.cbClsExtra = 0;
        windowClass.cbWndExtra = 0;
        windowClass.hInstance = TclWinGetTclInstance();
        windowClass.hbrBackground = NULL;
        windowClass.lpszMenuName = NULL;
        windowClass.lpszClassName = "TclSocket";
        windowClass.lpfnWndProc = SocketProc;
        windowClass.hIcon = NULL;
        windowClass.hCursor = NULL;

        if (!RegisterClassA(&windowClass)) {
            TclWinConvertError(GetLastError());
            (*winSock.WSACleanup)();
            goto unloadLibrary;
        }
        
        /*
         * Initialize the winsock library and check the version number.
         */
    
        if ((*winSock.WSAStartup)(WSA_VERSION_REQD, &wsaData) != 0) {
            goto unloadLibrary;
        }
        if (wsaData.wVersion != WSA_VERSION_REQD) {
            (*winSock.WSACleanup)();
            goto unloadLibrary;
        }
    }

    /*
     * Check for per-thread initialization.
     */

    if (tsdPtr == NULL) {
        tsdPtr = TCL_TSD_INIT(&dataKey);
        tsdPtr->socketList = NULL;
        tsdPtr->hwnd = NULL;

        tsdPtr->threadId = Tcl_GetCurrentThread();
        
        tsdPtr->readyEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
        tsdPtr->socketListLock = CreateEvent(NULL, FALSE, TRUE, NULL);
        tsdPtr->socketThread = CreateThread(NULL, 8000, SocketThread,
                tsdPtr, 0, &id);
        SetThreadPriority(tsdPtr->socketThread, THREAD_PRIORITY_HIGHEST); 

        if (tsdPtr->socketThread == NULL) {
            goto unloadLibrary;
        }
        

        /*
         * Wait for the thread to signal that the window has
         * been created and is ready to go.  Timeout after twenty
         * seconds.
         */
        
        if (WaitForSingleObject(tsdPtr->readyEvent, 20000) == WAIT_TIMEOUT) {
            goto unloadLibrary;
        }

        if (tsdPtr->hwnd == NULL) {
            goto unloadLibrary;
        }
        
        Tcl_CreateEventSource(SocketSetupProc, SocketCheckProc, NULL);
        Tcl_CreateThreadExitHandler(SocketThreadExitHandler, NULL);
    }
    return;

unloadLibrary:
    if (tsdPtr != NULL) {
        if (tsdPtr->hwnd != NULL) {
            DestroyWindow(tsdPtr->hwnd);
        }
        if (tsdPtr->socketThread != NULL) {
            TerminateThread(tsdPtr->socketThread, 0);
            tsdPtr->socketThread = NULL;
        }
        CloseHandle(tsdPtr->readyEvent);
        CloseHandle(tsdPtr->socketListLock);
    }
    FreeLibrary(winSock.hInstance);
    winSock.hInstance = NULL;
    return;
}

/*
 *----------------------------------------------------------------------
 *
 * SocketsEnabled --
 *
 *      Check that the WinSock DLL is loaded and ready.
 *
 * Results:
 *      1 if it is.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

    /* ARGSUSED */
static int
SocketsEnabled()
{
    int enabled;
    Tcl_MutexLock(&socketMutex);
    enabled = (winSock.hInstance != NULL);
    Tcl_MutexUnlock(&socketMutex);
    return enabled;
}


/*
 *----------------------------------------------------------------------
 *
 * SocketExitHandler --
 *
 *      Callback invoked during exit clean up to delete the socket
 *      communication window and to release the WinSock DLL.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

    /* ARGSUSED */
static void
SocketExitHandler(clientData)
    ClientData clientData;              /* Not used. */
{
    Tcl_MutexLock(&socketMutex);
    if (winSock.hInstance) {
        UnregisterClassA("TclSocket", TclWinGetTclInstance());
        (*winSock.WSACleanup)();
        FreeLibrary(winSock.hInstance);
        winSock.hInstance = NULL;
    }
    initialized = 0;
    hostnameInitialized = 0;
    Tcl_MutexUnlock(&socketMutex);
}

/*
 *----------------------------------------------------------------------
 *
 * SocketThreadExitHandler --
 *
 *      Callback invoked during thread clean up to delete the socket
 *      event source.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Delete the event source.
 *
 *----------------------------------------------------------------------
 */

    /* ARGSUSED */
static void
SocketThreadExitHandler(clientData)
    ClientData clientData;              /* Not used. */
{
    ThreadSpecificData *tsdPtr = 
        (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);

    if (tsdPtr->socketThread != NULL) {

        PostMessage(tsdPtr->hwnd, SOCKET_TERMINATE, 0, 0);

        /*
         * Wait for the thread to terminate.  This ensures that we are
         * completely cleaned up before we leave this function. 
         */

        WaitForSingleObject(tsdPtr->socketThread, INFINITE);
        CloseHandle(tsdPtr->socketThread);
        CloseHandle(tsdPtr->readyEvent);
        CloseHandle(tsdPtr->socketListLock);

    }
    if (tsdPtr->hwnd != NULL) {
        DestroyWindow(tsdPtr->hwnd);
    }
    
    Tcl_DeleteEventSource(SocketSetupProc, SocketCheckProc, NULL);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpHasSockets --
 *
 *      This function determines whether sockets are available on the
 *      current system and returns an error in interp if they are not.
 *      Note that interp may be NULL.
 *
 * Results:
 *      Returns TCL_OK if the system supports sockets, or TCL_ERROR with
 *      an error in interp.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

int
TclpHasSockets(interp)
    Tcl_Interp *interp;
{
    Tcl_MutexLock(&socketMutex);
    InitSockets();
    Tcl_MutexUnlock(&socketMutex);

    if (SocketsEnabled()) {
        return TCL_OK;
    }
    if (interp != NULL) {
        Tcl_AppendResult(interp, "sockets are not available on this system",
                NULL);
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * SocketSetupProc --
 *
 *      This procedure is invoked before Tcl_DoOneEvent blocks waiting
 *      for an event.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Adjusts the block time if needed.
 *
 *----------------------------------------------------------------------
 */

void
SocketSetupProc(data, flags)
    ClientData data;            /* Not used. */
    int flags;                  /* Event flags as passed to Tcl_DoOneEvent. */
{
    SocketInfo *infoPtr;
    Tcl_Time blockTime = { 0, 0 };
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!(flags & TCL_FILE_EVENTS)) {
        return;
    }
    
    /*
     * Check to see if there is a ready socket.  If so, poll.
     */

    WaitForSingleObject(tsdPtr->socketListLock, INFINITE);
    for (infoPtr = tsdPtr->socketList; infoPtr != NULL; 
            infoPtr = infoPtr->nextPtr) {
        if (infoPtr->readyEvents & infoPtr->watchEvents) {
            Tcl_SetMaxBlockTime(&blockTime);
            break;
        }
    }
    SetEvent(tsdPtr->socketListLock);
}

/*
 *----------------------------------------------------------------------
 *
 * SocketCheckProc --
 *
 *      This procedure is called by Tcl_DoOneEvent to check the socket
 *      event source for events. 
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      May queue an event.
 *
 *----------------------------------------------------------------------
 */

static void
SocketCheckProc(data, flags)
    ClientData data;            /* Not used. */
    int flags;                  /* Event flags as passed to Tcl_DoOneEvent. */
{
    SocketInfo *infoPtr;
    SocketEvent *evPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!(flags & TCL_FILE_EVENTS)) {
        return;
    }
    
    /*
     * Queue events for any ready sockets that don't already have events
     * queued (caused by persistent states that won't generate WinSock
     * events).
     */

    WaitForSingleObject(tsdPtr->socketListLock, INFINITE);
    for (infoPtr = tsdPtr->socketList; infoPtr != NULL; 
            infoPtr = infoPtr->nextPtr) {
        if ((infoPtr->readyEvents & infoPtr->watchEvents)
                && !(infoPtr->flags & SOCKET_PENDING)) {
            infoPtr->flags |= SOCKET_PENDING;
            evPtr = (SocketEvent *) ckalloc(sizeof(SocketEvent));
            evPtr->header.proc = SocketEventProc;
            evPtr->socket = infoPtr->socket;
            Tcl_QueueEvent((Tcl_Event *) evPtr, TCL_QUEUE_TAIL);
        }
    }
    SetEvent(tsdPtr->socketListLock);
}

/*
 *----------------------------------------------------------------------
 *
 * SocketEventProc --
 *
 *      This procedure is called by Tcl_ServiceEvent when a socket event
 *      reaches the front of the event queue.  This procedure is
 *      responsible for notifying the generic channel code.
 *
 * Results:
 *      Returns 1 if the event was handled, meaning it should be removed
 *      from the queue.  Returns 0 if the event was not handled, meaning
 *      it should stay on the queue.  The only time the event isn't
 *      handled is if the TCL_FILE_EVENTS flag bit isn't set.
 *
 * Side effects:
 *      Whatever the channel callback procedures do.
 *
 *----------------------------------------------------------------------
 */

static int
SocketEventProc(evPtr, flags)
    Tcl_Event *evPtr;           /* Event to service. */
    int flags;                  /* Flags that indicate what events to
                                 * handle, such as TCL_FILE_EVENTS. */
{
    SocketInfo *infoPtr;
    SocketEvent *eventPtr = (SocketEvent *) evPtr;
    int mask = 0;
    int events;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    if (!(flags & TCL_FILE_EVENTS)) {
        return 0;
    }

    /*
     * Find the specified socket on the socket list.
     */

    WaitForSingleObject(tsdPtr->socketListLock, INFINITE);
    for (infoPtr = tsdPtr->socketList; infoPtr != NULL; 
            infoPtr = infoPtr->nextPtr) {
        if (infoPtr->socket == eventPtr->socket) {
            break;
        }
    }
    SetEvent(tsdPtr->socketListLock);
    
    /*
     * Discard events that have gone stale.
     */

    if (!infoPtr) {
        return 1;
    }

    infoPtr->flags &= ~SOCKET_PENDING;

    /*
     * Handle connection requests directly.
     */

    if (infoPtr->readyEvents & FD_ACCEPT) {
        TcpAccept(infoPtr);
        return 1;
    }


    /*
     * Mask off unwanted events and compute the read/write mask so 
     * we can notify the channel.
     */

    events = infoPtr->readyEvents & infoPtr->watchEvents;

    if (events & FD_CLOSE) {
        /*
         * If the socket was closed and the channel is still interested
         * in read events, then we need to ensure that we keep polling
         * for this event until someone does something with the channel.
         * Note that we do this before calling Tcl_NotifyChannel so we don't
         * have to watch out for the channel being deleted out from under
         * us.  This may cause a redundant trip through the event loop, but
         * it's simpler than trying to do unwind protection.
         */

        Tcl_Time blockTime = { 0, 0 };
        Tcl_SetMaxBlockTime(&blockTime);
        mask |= TCL_READABLE;
    } else if (events & FD_READ) {
        fd_set readFds;
        struct timeval timeout;

        /*
         * We must check to see if data is really available, since someone
         * could have consumed the data in the meantime.  Turn off async
         * notification so select will work correctly.  If the socket is
         * still readable, notify the channel driver, otherwise reset the
         * async select handler and keep waiting.
         */

        SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
                (WPARAM) UNSELECT, (LPARAM) infoPtr);

        FD_ZERO(&readFds);
        FD_SET(infoPtr->socket, &readFds);
        timeout.tv_usec = 0;
        timeout.tv_sec = 0;
 
        if ((*winSock.select)(0, &readFds, NULL, NULL, &timeout) != 0) {
            mask |= TCL_READABLE;
        } else {
            SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
                    (WPARAM) SELECT, (LPARAM) infoPtr);
            infoPtr->readyEvents &= ~(FD_READ);
        }
    }
    if (events & (FD_WRITE | FD_CONNECT)) {
        mask |= TCL_WRITABLE;
    }

    if (mask) {
        Tcl_NotifyChannel(infoPtr->channel, mask);
    }
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpBlockProc --
 *
 *      Sets a socket into blocking or non-blocking mode.
 *
 * Results:
 *      0 if successful, errno if there was an error.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
TcpBlockProc(instanceData, mode)
    ClientData  instanceData;   /* The socket to block/un-block. */
    int mode;                   /* TCL_MODE_BLOCKING or
                                 * TCL_MODE_NONBLOCKING. */
{
    SocketInfo *infoPtr = (SocketInfo *) instanceData;

    if (mode == TCL_MODE_NONBLOCKING) {
        infoPtr->flags |= SOCKET_ASYNC;
    } else {
        infoPtr->flags &= ~(SOCKET_ASYNC);
    }
    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpCloseProc --
 *
 *      This procedure is called by the generic IO level to perform
 *      channel type specific cleanup on a socket based channel
 *      when the channel is closed.
 *
 * Results:
 *      0 if successful, the value of errno if failed.
 *
 * Side effects:
 *      Closes the socket.
 *
 *----------------------------------------------------------------------
 */

    /* ARGSUSED */
static int
TcpCloseProc(instanceData, interp)
    ClientData instanceData;    /* The socket to close. */
    Tcl_Interp *interp;         /* Unused. */
{
    SocketInfo *infoPtr = (SocketInfo *) instanceData;
    SocketInfo **nextPtrPtr;
    int errorCode = 0;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (SocketsEnabled()) {
        
        /*
         * Clean up the OS socket handle.  The default Windows setting
         * for a socket is SO_DONTLINGER, which does a graceful shutdown
         * in the background.
         */
    
        if ((*winSock.closesocket)(infoPtr->socket) == SOCKET_ERROR) {
            TclWinConvertWSAError((*winSock.WSAGetLastError)());
            errorCode = Tcl_GetErrno();
        }
    }

    /*
     * Remove the socket from socketList.
     */

    WaitForSingleObject(tsdPtr->socketListLock, INFINITE);
    for (nextPtrPtr = &(tsdPtr->socketList); (*nextPtrPtr) != NULL;
         nextPtrPtr = &((*nextPtrPtr)->nextPtr)) {
        if ((*nextPtrPtr) == infoPtr) {
            (*nextPtrPtr) = infoPtr->nextPtr;
            break;
        }
    }
    SetEvent(tsdPtr->socketListLock);
    
    ckfree((char *) infoPtr);
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * NewSocketInfo --
 *
 *      This function allocates and initializes a new SocketInfo
 *      structure.
 *
 * Results:
 *      Returns a newly allocated SocketInfo.
 *
 * Side effects:
 *      Adds the socket to the global socket list.
 *
 *----------------------------------------------------------------------
 */

static SocketInfo *
NewSocketInfo(socket)
    SOCKET socket;
{
    SocketInfo *infoPtr;
    ThreadSpecificData *tsdPtr = TCL_TSD_INIT(&dataKey);

    infoPtr = (SocketInfo *) ckalloc((unsigned) sizeof(SocketInfo));
    infoPtr->socket = socket;
    infoPtr->flags = 0;
    infoPtr->watchEvents = 0;
    infoPtr->readyEvents = 0;
    infoPtr->selectEvents = 0;
    infoPtr->acceptEventCount = 0;
    infoPtr->acceptProc = NULL;
    infoPtr->lastError = 0;

    WaitForSingleObject(tsdPtr->socketListLock, INFINITE);
    infoPtr->nextPtr = tsdPtr->socketList;
    tsdPtr->socketList = infoPtr;
    SetEvent(tsdPtr->socketListLock);
    
    return infoPtr;
}

/*
 *----------------------------------------------------------------------
 *
 * CreateSocket --
 *
 *      This function opens a new socket and initializes the
 *      SocketInfo structure.
 *
 * Results:
 *      Returns a new SocketInfo, or NULL with an error in interp.
 *
 * Side effects:
 *      Adds a new socket to the socketList.
 *
 *----------------------------------------------------------------------
 */

static SocketInfo *
CreateSocket(interp, port, host, server, myaddr, myport, async)
    Tcl_Interp *interp;         /* For error reporting; can be NULL. */
    int port;                   /* Port number to open. */
    char *host;                 /* Name of host on which to open port. */
    int server;                 /* 1 if socket should be a server socket,
                                 * else 0 for a client socket. */
    char *myaddr;               /* Optional client-side address */
    int myport;                 /* Optional client-side port */
    int async;                  /* If nonzero, connect client socket
                                 * asynchronously. */
{
    u_long flag = 1;                    /* Indicates nonblocking mode. */
    int asyncConnect = 0;               /* Will be 1 if async connect is
                                         * in progress. */
    struct sockaddr_in sockaddr;        /* Socket address */
    struct sockaddr_in mysockaddr;      /* Socket address for client */
    SOCKET sock;
    SocketInfo *infoPtr;                /* The returned value. */
    ThreadSpecificData *tsdPtr = 
        (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);

    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (!SocketsEnabled()) {
        return NULL;
    }

    if (! CreateSocketAddress(&sockaddr, host, port)) {
        goto error;
    }
    if ((myaddr != NULL || myport != 0) &&
            ! CreateSocketAddress(&mysockaddr, myaddr, myport)) {
        goto error;
    }

    sock = (*winSock.socket)(AF_INET, SOCK_STREAM, 0);
    if (sock == INVALID_SOCKET) {
        goto error;
    }

    /*
     * Win-NT has a misfeature that sockets are inherited in child
     * processes by default.  Turn off the inherit bit.
     */

    SetHandleInformation( (HANDLE) sock, HANDLE_FLAG_INHERIT, 0 );
        
    /*
     * Set kernel space buffering
     */

    TclSockMinimumBuffers(sock, TCP_BUFFER_SIZE);

    if (server) {
        /*
         * Bind to the specified port.  Note that we must not call setsockopt
         * with SO_REUSEADDR because Microsoft allows addresses to be reused
         * even if they are still in use.
         *
         * Bind should not be affected by the socket having already been
         * set into nonblocking mode. If there is trouble, this is one place
         * to look for bugs.
         */
    
        if ((*winSock.bind)(sock, (struct sockaddr *) &sockaddr,
                sizeof(sockaddr)) == SOCKET_ERROR) {
            goto error;
        }

        /*
         * Set the maximum number of pending connect requests to the
         * max value allowed on each platform (Win32 and Win32s may be
         * different, and there may be differences between TCP/IP stacks).
         */
        
        if ((*winSock.listen)(sock, SOMAXCONN) == SOCKET_ERROR) {
            goto error;
        }

        /*
         * Add this socket to the global list of sockets.
         */

        infoPtr = NewSocketInfo(sock);

        /*
         * Set up the select mask for connection request events.
         */

        infoPtr->selectEvents = FD_ACCEPT;
        infoPtr->watchEvents |= FD_ACCEPT;

    } else {

        /*
         * Try to bind to a local port, if specified.
         */
        
        if (myaddr != NULL || myport != 0) { 
            if ((*winSock.bind)(sock, (struct sockaddr *) &mysockaddr,
                    sizeof(struct sockaddr)) == SOCKET_ERROR) {
                goto error;
            }
        }            
    
        /*
         * Set the socket into nonblocking mode if the connect should be
         * done in the background.
         */
    
        if (async) {
            if ((*winSock.ioctlsocket)(sock, FIONBIO, &flag) == SOCKET_ERROR) {
                goto error;
            }
        }

        /*
         * Attempt to connect to the remote socket.
         */

        if ((*winSock.connect)(sock, (struct sockaddr *) &sockaddr,
                sizeof(sockaddr)) == SOCKET_ERROR) {
            TclWinConvertWSAError((*winSock.WSAGetLastError)());
            if (Tcl_GetErrno() != EWOULDBLOCK) {
                goto error;
            }

            /*
             * The connection is progressing in the background.
             */

            asyncConnect = 1;
        }

        /*
         * Add this socket to the global list of sockets.
         */

        infoPtr = NewSocketInfo(sock);

        /*
         * Set up the select mask for read/write events.  If the connect
         * attempt has not completed, include connect events.
         */

        infoPtr->selectEvents = FD_READ | FD_WRITE | FD_CLOSE;
        if (asyncConnect) {
            infoPtr->flags |= SOCKET_ASYNC_CONNECT;
            infoPtr->selectEvents |= FD_CONNECT;
        }
    }

    /*
     * Register for interest in events in the select mask.  Note that this
     * automatically places the socket into non-blocking mode.
     */

    (*winSock.ioctlsocket)(sock, FIONBIO, &flag);
    SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
            (WPARAM) SELECT, (LPARAM) infoPtr);

    return infoPtr;

error:
    TclWinConvertWSAError((*winSock.WSAGetLastError)());
    if (interp != NULL) {
        Tcl_AppendResult(interp, "couldn't open socket: ",
                Tcl_PosixError(interp), (char *) NULL);
    }
    if (sock != INVALID_SOCKET) {
        (*winSock.closesocket)(sock);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * CreateSocketAddress --
 *
 *      This function initializes a sockaddr structure for a host and port.
 *
 * Results:
 *      1 if the host was valid, 0 if the host could not be converted to
 *      an IP address.
 *
 * Side effects:
 *      Fills in the *sockaddrPtr structure.
 *
 *----------------------------------------------------------------------
 */

static int
CreateSocketAddress(sockaddrPtr, host, port)
    struct sockaddr_in *sockaddrPtr;    /* Socket address */
    char *host;                         /* Host.  NULL implies INADDR_ANY */
    int port;                           /* Port number */
{
    struct hostent *hostent;            /* Host database entry */
    struct in_addr addr;                /* For 64/32 bit madness */

    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (!SocketsEnabled()) {
        Tcl_SetErrno(EFAULT);
        return 0;
    }

    (void) memset((char *) sockaddrPtr, '\0', sizeof(struct sockaddr_in));
    sockaddrPtr->sin_family = AF_INET;
    sockaddrPtr->sin_port = (*winSock.htons)((short) (port & 0xFFFF));
    if (host == NULL) {
        addr.s_addr = INADDR_ANY;
    } else {
        addr.s_addr = (*winSock.inet_addr)(host);
        if (addr.s_addr == INADDR_NONE) {
            hostent = (*winSock.gethostbyname)(host);
            if (hostent != NULL) {
                memcpy((char *) &addr,
                        (char *) hostent->h_addr_list[0],
                        (size_t) hostent->h_length);
            } else {
#ifdef  EHOSTUNREACH
                Tcl_SetErrno(EHOSTUNREACH);
#else
#ifdef ENXIO
                Tcl_SetErrno(ENXIO);
#endif
#endif
                return 0;       /* Error. */
            }
        }
    }

    /*
     * NOTE: On 64 bit machines the assignment below is rumored to not
     * do the right thing. Please report errors related to this if you
     * observe incorrect behavior on 64 bit machines such as DEC Alphas.
     * Should we modify this code to do an explicit memcpy?
     */

    sockaddrPtr->sin_addr.s_addr = addr.s_addr;
    return 1;   /* Success. */
}

/*
 *----------------------------------------------------------------------
 *
 * WaitForSocketEvent --
 *
 *      Waits until one of the specified events occurs on a socket.
 *
 * Results:
 *      Returns 1 on success or 0 on failure, with an error code in
 *      errorCodePtr.
 *
 * Side effects:
 *      Processes socket events off the system queue.
 *
 *----------------------------------------------------------------------
 */

static int
WaitForSocketEvent(infoPtr, events, errorCodePtr)
    SocketInfo *infoPtr;        /* Information about this socket. */
    int events;                 /* Events to look for. */
    int *errorCodePtr;          /* Where to store errors? */
{
    int result = 1;
    int oldMode;
    ThreadSpecificData *tsdPtr = 
        (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);

    /*
     * Be sure to disable event servicing so we are truly modal.
     */

    oldMode = Tcl_SetServiceMode(TCL_SERVICE_NONE);
    
    /*
     * Reset WSAAsyncSelect so we have a fresh set of events pending.
     */

    SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
            (WPARAM) UNSELECT, (LPARAM) infoPtr);

    SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
            (WPARAM) SELECT, (LPARAM) infoPtr);

    while (1) {

        if (infoPtr->lastError) {
            *errorCodePtr = infoPtr->lastError;
            result = 0;
            break;
        } else if (infoPtr->readyEvents & events) {
            break;
        } else if (infoPtr->flags & SOCKET_ASYNC) {
            *errorCodePtr = EWOULDBLOCK;
            result = 0;
            break;
        }

        /*
         * Wait until something happens.
         */
        WaitForSingleObject(tsdPtr->readyEvent, INFINITE);
    }
    
    (void) Tcl_SetServiceMode(oldMode);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_OpenTcpClient --
 *
 *      Opens a TCP client socket and creates a channel around it.
 *
 * Results:
 *      The channel or NULL if failed.  An error message is returned
 *      in the interpreter on failure.
 *
 * Side effects:
 *      Opens a client socket and creates a new channel.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_OpenTcpClient(interp, port, host, myaddr, myport, async)
    Tcl_Interp *interp;                 /* For error reporting; can be NULL. */
    int port;                           /* Port number to open. */
    char *host;                         /* Host on which to open port. */
    char *myaddr;                       /* Client-side address */
    int myport;                         /* Client-side port */
    int async;                          /* If nonzero, should connect
                                         * client socket asynchronously. */
{
    SocketInfo *infoPtr;
    char channelName[16 + TCL_INTEGER_SPACE];

    if (TclpHasSockets(interp) != TCL_OK) {
        return NULL;
    }

    /*
     * Create a new client socket and wrap it in a channel.
     */

    infoPtr = CreateSocket(interp, port, host, 0, myaddr, myport, async);
    if (infoPtr == NULL) {
        return NULL;
    }

    wsprintfA(channelName, "sock%d", infoPtr->socket);

    infoPtr->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
            (ClientData) infoPtr, (TCL_READABLE | TCL_WRITABLE));
    if (Tcl_SetChannelOption(interp, infoPtr->channel, "-translation",
            "auto crlf") == TCL_ERROR) {
        Tcl_Close((Tcl_Interp *) NULL, infoPtr->channel);
        return (Tcl_Channel) NULL;
    }
    if (Tcl_SetChannelOption(NULL, infoPtr->channel, "-eofchar", "")
            == TCL_ERROR) {
        Tcl_Close((Tcl_Interp *) NULL, infoPtr->channel);
        return (Tcl_Channel) NULL;
    }
    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_MakeTcpClientChannel --
 *
 *      Creates a Tcl_Channel from an existing client TCP socket.
 *
 * Results:
 *      The Tcl_Channel wrapped around the preexisting TCP socket.
 *
 * Side effects:
 *      None.
 *
 * NOTE: Code contributed by Mark Diekhans (markd@grizzly.com)
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_MakeTcpClientChannel(sock)
    ClientData sock;            /* The socket to wrap up into a channel. */
{
    SocketInfo *infoPtr;
    char channelName[16 + TCL_INTEGER_SPACE];
    ThreadSpecificData *tsdPtr;

    if (TclpHasSockets(NULL) != TCL_OK) {
        return NULL;
    }

    tsdPtr = (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);

    /*
     * Set kernel space buffering and non-blocking.
     */

    TclSockMinimumBuffers((SOCKET) sock, TCP_BUFFER_SIZE);

    infoPtr = NewSocketInfo((SOCKET) sock);

    /*
     * Start watching for read/write events on the socket.
     */

    infoPtr->selectEvents = FD_READ | FD_CLOSE | FD_WRITE;
    SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
            (WPARAM) SELECT, (LPARAM) infoPtr);

    wsprintfA(channelName, "sock%d", infoPtr->socket);
    infoPtr->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
            (ClientData) infoPtr, (TCL_READABLE | TCL_WRITABLE));
    Tcl_SetChannelOption(NULL, infoPtr->channel, "-translation", "auto crlf");
    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_OpenTcpServer --
 *
 *      Opens a TCP server socket and creates a channel around it.
 *
 * Results:
 *      The channel or NULL if failed.  An error message is returned
 *      in the interpreter on failure.
 *
 * Side effects:
 *      Opens a server socket and creates a new channel.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
Tcl_OpenTcpServer(interp, port, host, acceptProc, acceptProcData)
    Tcl_Interp *interp;                 /* For error reporting - may be
                                         * NULL. */
    int port;                           /* Port number to open. */
    char *host;                         /* Name of local host. */
    Tcl_TcpAcceptProc *acceptProc;      /* Callback for accepting connections
                                         * from new clients. */
    ClientData acceptProcData;          /* Data for the callback. */
{
    SocketInfo *infoPtr;
    char channelName[16 + TCL_INTEGER_SPACE];

    if (TclpHasSockets(interp) != TCL_OK) {
        return NULL;
    }

    /*
     * Create a new client socket and wrap it in a channel.
     */

    infoPtr = CreateSocket(interp, port, host, 1, NULL, 0, 0);
    if (infoPtr == NULL) {
        return NULL;
    }

    infoPtr->acceptProc = acceptProc;
    infoPtr->acceptProcData = acceptProcData;

    wsprintfA(channelName, "sock%d", infoPtr->socket);

    infoPtr->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
            (ClientData) infoPtr, 0);
    if (Tcl_SetChannelOption(interp, infoPtr->channel, "-eofchar", "")
            == TCL_ERROR) {
        Tcl_Close((Tcl_Interp *) NULL, infoPtr->channel);
        return (Tcl_Channel) NULL;
    }

    return infoPtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpAccept --
 *      Accept a TCP socket connection.  This is called by
 *      SocketEventProc and it in turns calls the registered accept
 *      procedure.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Invokes the accept proc which may invoke arbitrary Tcl code.
 *
 *----------------------------------------------------------------------
 */

static void
TcpAccept(infoPtr)
    SocketInfo *infoPtr;        /* Socket to accept. */
{
    SOCKET newSocket;
    SocketInfo *newInfoPtr;
    struct sockaddr_in addr;
    int len;
    char channelName[16 + TCL_INTEGER_SPACE];
    ThreadSpecificData *tsdPtr = 
        (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);

    /*
     * Accept the incoming connection request.
     */

    len = sizeof(struct sockaddr_in);

    newSocket = (*winSock.accept)(infoPtr->socket,
            (struct sockaddr *)&addr,
            &len);
    
    /*
     * Clear the ready mask so we can detect the next connection request.
     * Note that connection requests are level triggered, so if there is
     * a request already pending, a new event will be generated.
     */
    
    if (newSocket == INVALID_SOCKET) {
        infoPtr->acceptEventCount = 0;
        infoPtr->readyEvents &= ~(FD_ACCEPT);
        return;
    } 

    /*
     * It is possible that more than one FD_ACCEPT has been sent, so an extra
     * count must be kept.  Decrement the count, and reset the readyEvent bit
     * if the count is no longer > 0.
     */
    
    infoPtr->acceptEventCount--;

    if (infoPtr->acceptEventCount <= 0) {
        infoPtr->readyEvents &= ~(FD_ACCEPT);
    }

    /*
     * Win-NT has a misfeature that sockets are inherited in child
     * processes by default.  Turn off the inherit bit.
     */
    
    SetHandleInformation( (HANDLE) newSocket, HANDLE_FLAG_INHERIT, 0 );
    
    /*
     * Add this socket to the global list of sockets.
     */
    
    newInfoPtr = NewSocketInfo(newSocket);
    
    /*
     * Select on read/write events and create the channel.
     */
    
    newInfoPtr->selectEvents = (FD_READ | FD_WRITE | FD_CLOSE);
    SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
            (WPARAM) SELECT, (LPARAM) newInfoPtr);
    
    wsprintfA(channelName, "sock%d", newInfoPtr->socket);
    newInfoPtr->channel = Tcl_CreateChannel(&tcpChannelType, channelName,
            (ClientData) newInfoPtr, (TCL_READABLE | TCL_WRITABLE));
    if (Tcl_SetChannelOption(NULL, newInfoPtr->channel, "-translation",
            "auto crlf") == TCL_ERROR) {
        Tcl_Close((Tcl_Interp *) NULL, newInfoPtr->channel);
        return;
    }
    if (Tcl_SetChannelOption(NULL, newInfoPtr->channel, "-eofchar", "")
            == TCL_ERROR) {
        Tcl_Close((Tcl_Interp *) NULL, newInfoPtr->channel);
        return;
    }
    
    /*
     * Invoke the accept callback procedure.
     */
    
    if (infoPtr->acceptProc != NULL) {
        (infoPtr->acceptProc) (infoPtr->acceptProcData,
                newInfoPtr->channel,
                (*winSock.inet_ntoa)(addr.sin_addr),
                (*winSock.ntohs)(addr.sin_port));
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TcpInputProc --
 *
 *      This procedure is called by the generic IO level to read data from
 *      a socket based channel.
 *
 * Results:
 *      The number of bytes read or -1 on error.
 *
 * Side effects:
 *      Consumes input from the socket.
 *
 *----------------------------------------------------------------------
 */

static int
TcpInputProc(instanceData, buf, toRead, errorCodePtr)
    ClientData instanceData;            /* The socket state. */
    char *buf;                          /* Where to store data. */
    int toRead;                         /* Maximum number of bytes to read. */
    int *errorCodePtr;                  /* Where to store error codes. */
{
    SocketInfo *infoPtr = (SocketInfo *) instanceData;
    int bytesRead;
    int error;
    ThreadSpecificData *tsdPtr = 
        (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);
    
    *errorCodePtr = 0;

    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (!SocketsEnabled()) {
        *errorCodePtr = EFAULT;
        return -1;
    }

    /*
     * First check to see if EOF was already detected, to prevent
     * calling the socket stack after the first time EOF is detected.
     */

    if (infoPtr->flags & SOCKET_EOF) {
        return 0;
    }

    /*
     * Check to see if the socket is connected before trying to read.
     */

    if ((infoPtr->flags & SOCKET_ASYNC_CONNECT)
            && ! WaitForSocketEvent(infoPtr,  FD_CONNECT, errorCodePtr)) {
        return -1;
    }
    
    /*
     * No EOF, and it is connected, so try to read more from the socket.
     * Note that we clear the FD_READ bit because read events are level
     * triggered so a new event will be generated if there is still data
     * available to be read.  We have to simulate blocking behavior here
     * since we are always using non-blocking sockets.
     */

    while (1) {
        SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
                (WPARAM) UNSELECT, (LPARAM) infoPtr);
        bytesRead = (*winSock.recv)(infoPtr->socket, buf, toRead, 0);
        infoPtr->readyEvents &= ~(FD_READ);
  
        /*
         * Check for end-of-file condition or successful read.
         */
  
        if (bytesRead == 0) {
            infoPtr->flags |= SOCKET_EOF;
        }
        if (bytesRead != SOCKET_ERROR) {
            break;
        }
  
        /*
         * If an error occurs after the FD_CLOSE has arrived,
         * then ignore the error and report an EOF.
         */
  
        if (infoPtr->readyEvents & FD_CLOSE) {
            infoPtr->flags |= SOCKET_EOF;
            bytesRead = 0;
            break;
        }
  
        /*
         * Check for error condition or underflow in non-blocking case.
         */
  
        error = (*winSock.WSAGetLastError)();
        if ((infoPtr->flags & SOCKET_ASYNC) || (error != WSAEWOULDBLOCK)) {
            TclWinConvertWSAError(error);
            *errorCodePtr = Tcl_GetErrno();
            bytesRead = -1;
            break;
        }

        /*
         * In the blocking case, wait until the file becomes readable
         * or closed and try again.
         */

        if (!WaitForSocketEvent(infoPtr, FD_READ|FD_CLOSE, errorCodePtr)) {
            bytesRead = -1;
            break;
        }
    }
    
    SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
            (WPARAM) SELECT, (LPARAM) infoPtr);
    
    return bytesRead;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpOutputProc --
 *
 *      This procedure is called by the generic IO level to write data
 *      to a socket based channel.
 *
 * Results:
 *      The number of bytes written or -1 on failure.
 *
 * Side effects:
 *      Produces output on the socket.
 *
 *----------------------------------------------------------------------
 */

static int
TcpOutputProc(instanceData, buf, toWrite, errorCodePtr)
    ClientData instanceData;            /* The socket state. */
    char *buf;                          /* Where to get data. */
    int toWrite;                        /* Maximum number of bytes to write. */
    int *errorCodePtr;                  /* Where to store error codes. */
{
    SocketInfo *infoPtr = (SocketInfo *) instanceData;
    int bytesWritten;
    int error;
    ThreadSpecificData *tsdPtr = 
        (ThreadSpecificData *)TclThreadDataKeyGet(&dataKey);

    *errorCodePtr = 0;

    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (!SocketsEnabled()) {
        *errorCodePtr = EFAULT;
        return -1;
    }

    /*
     * Check to see if the socket is connected before trying to write.
     */
    
    if ((infoPtr->flags & SOCKET_ASYNC_CONNECT)
            && ! WaitForSocketEvent(infoPtr,  FD_CONNECT, errorCodePtr)) {
        return -1;
    }

    while (1) {
        SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
                (WPARAM) UNSELECT, (LPARAM) infoPtr);

        bytesWritten = (*winSock.send)(infoPtr->socket, buf, toWrite, 0);
        if (bytesWritten != SOCKET_ERROR) {
            /*
             * Since Windows won't generate a new write event until we hit
             * an overflow condition, we need to force the event loop to
             * poll until the condition changes.
             */

            if (infoPtr->watchEvents & FD_WRITE) {
                Tcl_Time blockTime = { 0, 0 };
                Tcl_SetMaxBlockTime(&blockTime);
            }           
            break;
        }
        
        /*
         * Check for error condition or overflow.  In the event of overflow, we
         * need to clear the FD_WRITE flag so we can detect the next writable
         * event.  Note that Windows only sends a new writable event after a
         * send fails with WSAEWOULDBLOCK.
         */

        error = (*winSock.WSAGetLastError)();
        if (error == WSAEWOULDBLOCK) {
            infoPtr->readyEvents &= ~(FD_WRITE);
            if (infoPtr->flags & SOCKET_ASYNC) {
                *errorCodePtr = EWOULDBLOCK;
                bytesWritten = -1;
                break;
            } 
        } else {
            TclWinConvertWSAError(error);
            *errorCodePtr = Tcl_GetErrno();
            bytesWritten = -1;
            break;
        }

        /*
         * In the blocking case, wait until the file becomes writable
         * or closed and try again.
         */

        if (!WaitForSocketEvent(infoPtr, FD_WRITE|FD_CLOSE, errorCodePtr)) {
            bytesWritten = -1;
            break;
        }
    }

    SendMessage(tsdPtr->hwnd, SOCKET_SELECT,
            (WPARAM) SELECT, (LPARAM) infoPtr);
    
    return bytesWritten;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpGetOptionProc --
 *
 *      Computes an option value for a TCP socket based channel, or a
 *      list of all options and their values.
 *
 *      Note: This code is based on code contributed by John Haxby.
 *
 * Results:
 *      A standard Tcl result. The value of the specified option or a
 *      list of all options and their values is returned in the
 *      supplied DString.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
TcpGetOptionProc(instanceData, interp, optionName, dsPtr)
    ClientData instanceData;            /* Socket state. */
    Tcl_Interp *interp;                 /* For error reporting - can be NULL */
    char *optionName;                   /* Name of the option to
                                         * retrieve the value for, or
                                         * NULL to get all options and
                                         * their values. */
    Tcl_DString *dsPtr;                 /* Where to store the computed
                                         * value; initialized by caller. */
{
    SocketInfo *infoPtr;
    struct sockaddr_in sockname;
    struct sockaddr_in peername;
    struct hostent *hostEntPtr;
    SOCKET sock;
    int size = sizeof(struct sockaddr_in);
    size_t len = 0;
    char buf[TCL_INTEGER_SPACE];

    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (!SocketsEnabled()) {
        if (interp) {
            Tcl_AppendResult(interp, "winsock is not initialized", NULL);
        }
        return TCL_ERROR;
    }
    
    infoPtr = (SocketInfo *) instanceData;
    sock = (int) infoPtr->socket;
    if (optionName != (char *) NULL) {
        len = strlen(optionName);
    }

    if ((len > 1) && (optionName[1] == 'e') &&
            (strncmp(optionName, "-error", len) == 0)) {
        int optlen;
        int err, ret;
    
        optlen = sizeof(int);
        ret = TclWinGetSockOpt(sock, SOL_SOCKET, SO_ERROR,
                (char *)&err, &optlen);
        if (ret == SOCKET_ERROR) {
            err = (*winSock.WSAGetLastError)();
        }
        if (err) {
            TclWinConvertWSAError(err);
            Tcl_DStringAppend(dsPtr, Tcl_ErrnoMsg(Tcl_GetErrno()), -1);
        }
        return TCL_OK;
    }

    if ((len == 0) ||
            ((len > 1) && (optionName[1] == 'p') &&
                    (strncmp(optionName, "-peername", len) == 0))) {
        if ((*winSock.getpeername)(sock, (struct sockaddr *) &peername, &size)
                == 0) {
            if (len == 0) {
                Tcl_DStringAppendElement(dsPtr, "-peername");
                Tcl_DStringStartSublist(dsPtr);
            }
            Tcl_DStringAppendElement(dsPtr,
                    (*winSock.inet_ntoa)(peername.sin_addr));
            hostEntPtr = (*winSock.gethostbyaddr)(
                (char *) &(peername.sin_addr), sizeof(peername.sin_addr),
                AF_INET);
            if (hostEntPtr != (struct hostent *) NULL) {
                Tcl_DStringAppendElement(dsPtr, hostEntPtr->h_name);
            } else {
                Tcl_DStringAppendElement(dsPtr,
                        (*winSock.inet_ntoa)(peername.sin_addr));
            }
            TclFormatInt(buf, (*winSock.ntohs)(peername.sin_port));
            Tcl_DStringAppendElement(dsPtr, buf);
            if (len == 0) {
                Tcl_DStringEndSublist(dsPtr);
            } else {
                return TCL_OK;
            }
        } else {
            /*
             * getpeername failed - but if we were asked for all the options
             * (len==0), don't flag an error at that point because it could
             * be an fconfigure request on a server socket. (which have
             * no peer). {copied from unix/tclUnixChan.c}
             */
            if (len) {
                TclWinConvertWSAError((*winSock.WSAGetLastError)());
                if (interp) {
                    Tcl_AppendResult(interp, "can't get peername: ",
                                     Tcl_PosixError(interp),
                                     (char *) NULL);
                }
                return TCL_ERROR;
            }
        }
    }

    if ((len == 0) ||
            ((len > 1) && (optionName[1] == 's') &&
                    (strncmp(optionName, "-sockname", len) == 0))) {
        if ((*winSock.getsockname)(sock, (struct sockaddr *) &sockname, &size)
                == 0) {
            if (len == 0) {
                Tcl_DStringAppendElement(dsPtr, "-sockname");
                Tcl_DStringStartSublist(dsPtr);
            }
            Tcl_DStringAppendElement(dsPtr,
                    (*winSock.inet_ntoa)(sockname.sin_addr));
            hostEntPtr = (*winSock.gethostbyaddr)(
                (char *) &(sockname.sin_addr), sizeof(peername.sin_addr),
                AF_INET);
            if (hostEntPtr != (struct hostent *) NULL) {
                Tcl_DStringAppendElement(dsPtr, hostEntPtr->h_name);
            } else {
                Tcl_DStringAppendElement(dsPtr,
                        (*winSock.inet_ntoa)(sockname.sin_addr));
            }
            TclFormatInt(buf, (*winSock.ntohs)(sockname.sin_port));
            Tcl_DStringAppendElement(dsPtr, buf);
            if (len == 0) {
                Tcl_DStringEndSublist(dsPtr);
            } else {
                return TCL_OK;
            }
        } else {
            if (interp) {
                TclWinConvertWSAError((*winSock.WSAGetLastError)());
                Tcl_AppendResult(interp, "can't get sockname: ",
                                 Tcl_PosixError(interp),
                                 (char *) NULL);
            }
            return TCL_ERROR;
        }
    }

    if (len > 0) {
        return Tcl_BadChannelOption(interp, optionName, "peername sockname");
    }

    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TcpWatchProc --
 *
 *      Informs the channel driver of the events that the generic
 *      channel code wishes to receive on this socket.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      May cause the notifier to poll if any of the specified 
 *      conditions are already true.
 *
 *----------------------------------------------------------------------
 */

static void
TcpWatchProc(instanceData, mask)
    ClientData instanceData;            /* The socket state. */
    int mask;                           /* Events of interest; an OR-ed
                                         * combination of TCL_READABLE,
                                         * TCL_WRITABLE and TCL_EXCEPTION. */
{
    SocketInfo *infoPtr = (SocketInfo *) instanceData;
    
    /*
     * Update the watch events mask.
     */
    
    infoPtr->watchEvents = 0;
    if (mask & TCL_READABLE) {
        infoPtr->watchEvents |= (FD_READ|FD_CLOSE|FD_ACCEPT);
    }
    if (mask & TCL_WRITABLE) {
        infoPtr->watchEvents |= (FD_WRITE|FD_CONNECT);
    }

    /*
     * If there are any conditions already set, then tell the notifier to poll
     * rather than block.
     */

    if (infoPtr->readyEvents & infoPtr->watchEvents) {
        Tcl_Time blockTime = { 0, 0 };
        Tcl_SetMaxBlockTime(&blockTime);
    }           
}

/*
 *----------------------------------------------------------------------
 *
 * TcpGetProc --
 *
 *      Called from Tcl_GetChannelHandle to retrieve an OS handle from inside
 *      a TCP socket based channel.
 *
 * Results:
 *      Returns TCL_OK with the socket in handlePtr.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
TcpGetHandleProc(instanceData, direction, handlePtr)
    ClientData instanceData;    /* The socket state. */
    int direction;              /* Not used. */
    ClientData *handlePtr;      /* Where to store the handle.  */
{
    SocketInfo *statePtr = (SocketInfo *) instanceData;

    *handlePtr = (ClientData) statePtr->socket;
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * SocketThread --
 *
 *      Helper thread used to manage the socket event handling window.
 *
 * Results:
 *      1 if unable to create socket event window, 0 otherwise.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static DWORD WINAPI
SocketThread(LPVOID arg)
{
    MSG msg;
    ThreadSpecificData *tsdPtr = (ThreadSpecificData *)(arg);

    tsdPtr->hwnd = CreateWindowA("TclSocket", "TclSocket", 
            WS_TILED, 0, 0, 0, 0, NULL, NULL, windowClass.hInstance, NULL);

    /*
     * Signal the main thread that the window has been created
     * and that the socket thread is ready to go.
     */
    
    SetEvent(tsdPtr->readyEvent);
    
    if (tsdPtr->hwnd == NULL) {
        return 1;
    } else {
        /*
         * store the tsdPtr, it's from a different thread, so it's
         * not directly accessible, but needed.
         */

#ifdef _WIN64
        SetWindowLongPtr(tsdPtr->hwnd, GWLP_USERDATA, (LONG) tsdPtr);
#else
        SetWindowLong(tsdPtr->hwnd, GWL_USERDATA, (LONG) tsdPtr);
#endif
    }

    while (1) {
        /*
         * Process all outstanding messages on the socket window.
         */

        while (PeekMessage(&msg, tsdPtr->hwnd, 0, 0, PM_REMOVE)) {
            DispatchMessage(&msg);
        }
        WaitMessage();
    }
}


/*
 *----------------------------------------------------------------------
 *
 * SocketProc --
 *
 *      This function is called when WSAAsyncSelect has been used
 *      to register interest in a socket event, and the event has
 *      occurred.
 *
 * Results:
 *      0 on success.
 *
 * Side effects:
 *      The flags for the given socket are updated to reflect the
 *      event that occured.
 *
 *----------------------------------------------------------------------
 */

static LRESULT CALLBACK
SocketProc(hwnd, message, wParam, lParam)
    HWND hwnd;
    UINT message;
    WPARAM wParam;
    LPARAM lParam;
{
    int event, error;
    SOCKET socket;
    SocketInfo *infoPtr;
    ThreadSpecificData *tsdPtr =
#ifdef _WIN64
        (ThreadSpecificData *) GetWindowLongPtr(hwnd, GWLP_USERDATA);
#else
        (ThreadSpecificData *) GetWindowLong(hwnd, GWL_USERDATA);
#endif

    switch (message) {

        default:
            return DefWindowProc(hwnd, message, wParam, lParam);
            break;
            
        case SOCKET_MESSAGE:
            event = WSAGETSELECTEVENT(lParam);
            error = WSAGETSELECTERROR(lParam);
            socket = (SOCKET) wParam;

            /*
             * Find the specified socket on the socket list and update its
             * eventState flag.
             */

            WaitForSingleObject(tsdPtr->socketListLock, INFINITE);
            for (infoPtr = tsdPtr->socketList; infoPtr != NULL; 
                 infoPtr = infoPtr->nextPtr) {
                if (infoPtr->socket == socket) {
                    /*
                     * Update the socket state.
                     */

                    /*
                     * A count of FD_ACCEPTS is stored, so if an FD_CLOSE event
                     * happens, then clear the FD_ACCEPT count.  Otherwise,
                     * increment the count if the current event is and
                     * FD_ACCEPT.
                     */
                    
                    if (event & FD_CLOSE) {
                        infoPtr->acceptEventCount = 0;
                        infoPtr->readyEvents &= ~(FD_WRITE|FD_ACCEPT);
                    } else if (event & FD_ACCEPT) {
                        infoPtr->acceptEventCount++;
                    }

                    if (event & FD_CONNECT) {
                        /*
                         * The socket is now connected,
                         * clear the async connect flag.
                         */
                        
                        infoPtr->flags &= ~(SOCKET_ASYNC_CONNECT);
                        
                        /*
                         * Remember any error that occurred so we can report
                         * connection failures.
                         */
                        
                        if (error != ERROR_SUCCESS) {
                            TclWinConvertWSAError(error);
                            infoPtr->lastError = Tcl_GetErrno();
                        }
                        
                    } 
                    if(infoPtr->flags & SOCKET_ASYNC_CONNECT) {
                        infoPtr->flags &= ~(SOCKET_ASYNC_CONNECT);
                        if (error != ERROR_SUCCESS) {
                            TclWinConvertWSAError(error);
                            infoPtr->lastError = Tcl_GetErrno();
                        }
                        infoPtr->readyEvents |= FD_WRITE;
                    }
                    infoPtr->readyEvents |= event;

                    /*
                     * Wake up the Main Thread.
                     */
                    SetEvent(tsdPtr->readyEvent);
                    Tcl_ThreadAlert(tsdPtr->threadId);
                    break;
                }
            }
            SetEvent(tsdPtr->socketListLock);
            break;
        case SOCKET_SELECT:
            infoPtr = (SocketInfo *) lParam;
            if (wParam == SELECT) {

                (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, hwnd,
                        SOCKET_MESSAGE, infoPtr->selectEvents);
            } else {
                /*
                 * Clear the selection mask
                 */
                
                (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, hwnd, 0, 0);
            }
            break;
        case SOCKET_TERMINATE:
            ExitThread(0);
            break;
    }

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_GetHostName --
 *
 *      Returns the name of the local host.
 *
 * Results:
 *      A string containing the network name for this machine, or
 *      an empty string if we can't figure out the name.  The caller 
 *      must not modify or free this string.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

char *
Tcl_GetHostName()
{
    DWORD length;
    WCHAR wbuf[MAX_COMPUTERNAME_LENGTH + 1];

    Tcl_MutexLock(&socketMutex);
    InitSockets();

    if (hostnameInitialized) {
        Tcl_MutexUnlock(&socketMutex);
        return hostname;
    }
    Tcl_MutexUnlock(&socketMutex);
        
    if (TclpHasSockets(NULL) == TCL_OK) {
        /*
         * INTL: bug
         */

        if ((*winSock.gethostname)(hostname, sizeof(hostname)) == 0) {
            Tcl_MutexLock(&socketMutex);
            hostnameInitialized = 1;
            Tcl_MutexUnlock(&socketMutex);
            return hostname;
        }
    }
    Tcl_MutexLock(&socketMutex);
    length = sizeof(hostname);
    if ((*tclWinProcs->getComputerNameProc)(wbuf, &length) != 0) {
        /*
         * Convert string from native to UTF then change to lowercase.
         */

        Tcl_DString ds;

        lstrcpynA(hostname, Tcl_WinTCharToUtf((TCHAR *) wbuf, -1, &ds),
                sizeof(hostname));
        Tcl_DStringFree(&ds);
        Tcl_UtfToLower(hostname);
    } else {
        hostname[0] = '\0';
    }
    hostnameInitialized = 1;
    Tcl_MutexUnlock(&socketMutex);
    return hostname;
}

/*
 *----------------------------------------------------------------------
 *
 * TclWinGetSockOpt, et al. --
 *
 *      These functions are wrappers that let us bind the WinSock
 *      API dynamically so we can run on systems that don't have
 *      the wsock32.dll.  We need wrappers for these interfaces
 *      because they are called from the generic Tcl code.
 *
 * Results:
 *      As defined for each function.
 *
 * Side effects:
 *      As defined for each function.
 *
 *----------------------------------------------------------------------
 */

int
TclWinGetSockOpt(SOCKET s, int level, int optname, char * optval,
        int FAR *optlen)
{
    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (!SocketsEnabled()) {
        return SOCKET_ERROR;
    }
    
    return (*winSock.getsockopt)(s, level, optname, optval, optlen);
}

int
TclWinSetSockOpt(SOCKET s, int level, int optname, const char * optval,
        int optlen)
{
    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */
    if (!SocketsEnabled()) {
        return SOCKET_ERROR;
    }

    return (*winSock.setsockopt)(s, level, optname, optval, optlen);
}

u_short
TclWinNToHS(u_short netshort)
{
    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */

    if (!SocketsEnabled()) {
        return (u_short) -1;
    }

    return (*winSock.ntohs)(netshort);
}

struct servent *
TclWinGetServByName(const char * name, const char * proto)
{
    /*
     * Check that WinSock is initialized; do not call it if not, to
     * prevent system crashes. This can happen at exit time if the exit
     * handler for WinSock ran before other exit handlers that want to
     * use sockets.
     */
    if (!SocketsEnabled()) {
        return (struct servent *) NULL;
    }

    return (*winSock.getservbyname)(name, proto);
}

/* End of tclwinsock.c */