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tclWinSock.c

/* 
 * 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 1.3 1998/09/14 18:40:20 stanton Exp $
 */

#include "tclInt.h"
#include "tclPort.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. */

/*
 * 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. */
    HWND hwnd;                /* Handle to window for socket messages. */
    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

/*
 * 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. */
    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 */

/*
 * Every open socket has an entry on the following list.
 */

static SocketInfo *socketList;

/*
 * 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       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));

/*
 * 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.
 *
 * 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()
{
    WSADATA wsaData;
    OSVERSIONINFO info;
    WNDCLASS class;

    initialized = 1;
    Tcl_CreateExitHandler(SocketExitHandler, (ClientData) NULL);

    /*
     * Find out if we're running on Win32s.
     */

    info.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
    GetVersionEx(&info);

    /*
     * Check to see if Sockets are supported on this system.  Since
     * win32s panics if we call WSAStartup on a system that doesn't
     * have winsock.dll, we need to look for it on the system first.
     * If we find winsock, then load the library and initialize the
     * stub table.
     */

    if ((info.dwPlatformId != VER_PLATFORM_WIN32s)
          || (SearchPath(NULL, "WINSOCK", ".DLL", 0, NULL, NULL) != 0)) {
      winSock.hInstance = LoadLibrary("wsock32.dll");
    } else {
      winSock.hInstance = NULL;
    }

    /*
     * Initialize the function table.
     */

    if (winSock.hInstance == NULL) {
      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;
    }
    
    /*
     * 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;
    }

    /*
     * 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.
     */

    class.style = 0;
    class.cbClsExtra = 0;
    class.cbWndExtra = 0;
    class.hInstance = TclWinGetTclInstance();
    class.hbrBackground = NULL;
    class.lpszMenuName = NULL;
    class.lpszClassName = "TclSocket";
    class.lpfnWndProc = SocketProc;
    class.hIcon = NULL;
    class.hCursor = NULL;

    if (RegisterClass(&class)) {
      winSock.hwnd = CreateWindow("TclSocket", "TclSocket", WS_TILED, 0, 0,
            0, 0, NULL, NULL, class.hInstance, NULL);
    } else {
      winSock.hwnd = NULL;
    }
    if (winSock.hwnd == NULL) {
      TclWinConvertError(GetLastError());
      (*winSock.WSACleanup)();
      goto unloadLibrary;
    }
    Tcl_CreateEventSource(SocketSetupProc, SocketCheckProc, NULL);
    return;

unloadLibrary:
    FreeLibrary(winSock.hInstance);
    winSock.hInstance = NULL;
    return;
}

/*
 *----------------------------------------------------------------------
 *
 * 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. */
{
    if (winSock.hInstance) {
      DestroyWindow(winSock.hwnd);
      UnregisterClass("TclSocket", TclWinGetTclInstance());
      (*winSock.WSACleanup)();
      FreeLibrary(winSock.hInstance);
      winSock.hInstance = NULL;
    }
    Tcl_DeleteEventSource(SocketSetupProc, SocketCheckProc, NULL);
    initialized = 0;
    hostnameInitialized = 0;
}

/*
 *----------------------------------------------------------------------
 *
 * TclHasSockets --
 *
 *    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
TclHasSockets(interp)
    Tcl_Interp *interp;
{
    if (!initialized) {
      InitSockets();
    }
    
    if (winSock.hInstance != NULL) {
      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 };

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

    for (infoPtr = socketList; infoPtr != NULL; infoPtr = infoPtr->nextPtr) {
      if (infoPtr->readyEvents & infoPtr->watchEvents) {
          Tcl_SetMaxBlockTime(&blockTime);
          break;
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * 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;

    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).
     */

    for (infoPtr = 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);
      }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * 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;

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

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

    for (infoPtr = socketList; infoPtr != NULL; infoPtr = infoPtr->nextPtr) {
      if (infoPtr->socket == eventPtr->socket) {
          break;
      }
    }

    /*
     * 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.
       */

      (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd, 0, 0);

      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 {
          (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
                SOCKET_MESSAGE, infoPtr->selectEvents);
          infoPtr->readyEvents &= ~(FD_READ);
      }

    }
    if (events & FD_WRITE) {
      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;

    /*
     * 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 (winSock.hInstance != NULL) {
        
      /*
         * 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.
     */

    for (nextPtrPtr = &socketList; (*nextPtrPtr) != NULL;
       nextPtrPtr = &((*nextPtrPtr)->nextPtr)) {
      if ((*nextPtrPtr) == infoPtr) {
          (*nextPtrPtr) = infoPtr->nextPtr;
          break;
      }
    }
    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;

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

    /*
     * 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 (winSock.hInstance == NULL) {
        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;
    }

    /*
     * 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);
    (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
          SOCKET_MESSAGE, infoPtr->selectEvents);

    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 (winSock.hInstance == NULL) {
        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? */
{
    MSG msg;
    int result = 1;
    int oldMode;

    /*
     * 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.
     */

    (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd, 0, 0);
    (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
          SOCKET_MESSAGE, infoPtr->selectEvents);

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

      while (PeekMessage(&msg, winSock.hwnd, 0, 0, PM_REMOVE)) {
          DispatchMessage(&msg);
      }
      
      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.
       */

      WaitMessage();
    }
    
    (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[20];

    if (TclHasSockets(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;
    }

    sprintf(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[20];

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

    /*
     * 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;
    (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
          SOCKET_MESSAGE, infoPtr->selectEvents);

    sprintf(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[20];

    if (TclHasSockets(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;

    sprintf(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[20];

    /*
     * 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.
     */

    infoPtr->readyEvents &= ~(FD_ACCEPT);

    if (newSocket == INVALID_SOCKET) {
        return;
    }

    /*
     * 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);
    (void) (*winSock.WSAAsyncSelect)(newInfoPtr->socket, winSock.hwnd, 
          SOCKET_MESSAGE, newInfoPtr->selectEvents);

    sprintf(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;
    
    *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 (winSock.hInstance == NULL) {
        *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) {
      (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
            0, 0);
      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;
      }
    }
    
    (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
          SOCKET_MESSAGE, infoPtr->selectEvents);
    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;

    *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 (winSock.hInstance == NULL) {
        *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) {
      (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
            0, 0);
      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;
      }
    }

    (void) (*winSock.WSAAsyncSelect)(infoPtr->socket, winSock.hwnd,
          SOCKET_MESSAGE, infoPtr->selectEvents);
    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[128];

    /*
     * 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 (winSock.hInstance == NULL) {
      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 == 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));
            }
            sprintf(buf, "%d", (*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));
            }
            sprintf(buf, "%d", (*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);
    }

    /*
     * 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_GetChannelFile 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;
}

/*
 *----------------------------------------------------------------------
 *
 * 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;

    if (message != SOCKET_MESSAGE) {
      return DefWindowProc(hwnd, message, wParam, lParam);
    }

    event = WSAGETSELECTEVENT(lParam);
    error = WSAGETSELECTERROR(lParam);
    socket = (SOCKET) wParam;

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

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

          if (event & FD_CLOSE) {
            infoPtr->readyEvents &= ~(FD_WRITE|FD_ACCEPT);
          }
          if (event & FD_CONNECT) {
            /*
             * The socket is now connected, so 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();
            }

          } 
          infoPtr->readyEvents |= event;
          break;
      }
    }

    /*
     * Flush the Tcl event queue before returning to the event loop.
     */

    Tcl_ServiceAll();

    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;
    char *p;

    if (hostnameInitialized) {
        return hostname;
    }

    if (TclHasSockets(NULL) == TCL_OK) {
      if ((*winSock.gethostname)(hostname, sizeof(hostname)) == 0) {
          hostnameInitialized = 1;
          return hostname;
      }
    }
    length = sizeof(hostname);
    if (GetComputerName(hostname, &length) != 0) {
      for (p = hostname; *p != '\0'; p++) {
          if (isupper(*((unsigned char *) p))) {
            *p = (char) tolower(*((unsigned char *) p));
          }
      }
    } else {
      hostname[0] = '\0';
    }
    hostnameInitialized = 1;
    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 PASCAL FAR
TclWinGetSockOpt(SOCKET s, int level, int optname, char FAR * 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 (winSock.hInstance == NULL) {
        return SOCKET_ERROR;
    }
    
    return (*winSock.getsockopt)(s, level, optname, optval, optlen);
}

int PASCAL FAR
TclWinSetSockOpt(SOCKET s, int level, int optname, const char FAR * 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 (winSock.hInstance == NULL) {
        return SOCKET_ERROR;
    }

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

u_short PASCAL FAR
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 (winSock.hInstance == NULL) {
        return (u_short) -1;
    }

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

struct servent FAR * PASCAL FAR
TclWinGetServByName(const char FAR * name, const char FAR * 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 (winSock.hInstance == NULL) {
        return (struct servent FAR *) NULL;
    }

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

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