static int		TcpConnect(Tcl_Interp *interp,
			    TcpState *state);
static void		InitSockets(void);
static TcpState *	NewSocketInfo(SOCKET socket);
static void		SocketExitHandler(void *clientData);
static LRESULT CALLBACK	SocketProc(HWND hwnd, UINT message, WPARAM wParam,
			    LPARAM lParam);
static int		SocketsEnabled(void);
static void		TcpAccept(TcpFdList *fds, SOCKET newSocket, address addr);
static int		WaitForConnect(TcpState *statePtr, int *errorCodePtr);
static int		WaitForSocketEvent(TcpState *statePtr, int events,
			    int *errorCodePtr);
static void		AddSocketInfoFd(TcpState *statePtr,  SOCKET socket);
static int		FindFDInList(TcpState *statePtr, SOCKET socket);
static DWORD WINAPI	SocketThread(LPVOID arg);

	/*
	 * Convert string from native to UTF then change to lowercase.
	 */

	Tcl_UtfToLower(Tcl_WCharToUtfDString(wbuf, TCL_INDEX_NONE, &ds));

    } else {
	if (TclpHasSockets(NULL) == TCL_OK) {
	    /*
	     * The buffer size of 256 is recommended by the MSDN page that
	     * documents gethostname() as being always adequate.
	     */

	    Tcl_DString inDs;

	    Tcl_DStringInit(&inDs);
	    Tcl_DStringSetLength(&inDs, 256);
	    if (gethostname(Tcl_DStringValue(&inDs),
		    Tcl_DStringLength(&inDs)) == 0) {
		Tcl_ExternalToUtfDStringEx(NULL, Tcl_DStringValue(&inDs),
			TCL_INDEX_NONE, TCL_ENCODING_NOCOMPLAIN, &ds);
	    }
	    Tcl_DStringFree(&inDs);
	}
    }

    *encodingPtr = Tcl_GetEncoding(NULL, "utf-8");
    *lengthPtr = Tcl_DStringLength(&ds);
    *valuePtr = (char *)Tcl_Alloc(*lengthPtr + 1);
    memcpy(*valuePtr, Tcl_DStringValue(&ds), *lengthPtr + 1);
    Tcl_DStringFree(&ds);

{
    return Tcl_GetString(TclGetProcessGlobalValue(&hostName));
}

/*
 *----------------------------------------------------------------------
 *
 * 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 (if non-NULL).
 *
 * Side effects:
 *	If not already prepared, initializes the TSD structure and socket
 *	message handling thread associated to the calling thread for the
 *	subsystem of the driver.
 *
 *----------------------------------------------------------------------
 */

int
TclpHasSockets(
    Tcl_Interp *interp)		/* Where to write an error message if sockets
				 * are not present, or NULL if no such message
				 * is to be written. */
{

    Tcl_MutexLock(&socketMutex);

    InitSockets();
    Tcl_MutexUnlock(&socketMutex);

    if (SocketsEnabled()) {
	return TCL_OK;
    }
    if (interp != NULL) {
	Tcl_SetObjResult(interp, Tcl_NewStringObj(
		"sockets are not available on this system", TCL_INDEX_NONE));
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpFinalizeSockets --
 *

    TcpState *statePtr = (TcpState *)instanceData;
    int bytesRead;
    DWORD 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 (GOT_BITS(statePtr->flags, SOCKET_EOF)) {
	return 0;

    TcpState *statePtr = (TcpState *)instanceData;
    int written;
    DWORD 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 if there is an async connect running.
     * For blocking sockets terminate connect, otherwise do one step.
     * For a non blocking socket return EWOULDBLOCK if connect not terminated
     */

    if (WaitForConnect(statePtr, errorCodePtr) != 0) {

{
    TcpState *statePtr = (TcpState *)instanceData;
    /* TIP #218 */
    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.
	 */

	while (statePtr->sockets != NULL) {
	    TcpFdList *thisfd = statePtr->sockets;

	    statePtr->sockets = thisfd->next;
	    if (closesocket(thisfd->fd) == SOCKET_ERROR) {
		Tcl_WinConvertError((DWORD) WSAGetLastError());
		errorCode = Tcl_GetErrno();
	    }
	    Tcl_Free(thisfd);
	}
    }

    if (statePtr->addrlist != NULL) {
        freeaddrinfo(statePtr->addrlist);
    }
    if (statePtr->myaddrlist != NULL) {
        freeaddrinfo(statePtr->myaddrlist);

    SOCKET sock;
    size_t len = 0;

    if (optionName != NULL) {
	len = strlen(optionName);
    }

    /*
     * 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_SetObjResult(interp, Tcl_NewStringObj(
		    "winsock is not initialized", -1));
	}
	return TCL_ERROR;
    }

    sock = statePtr->sockets->fd;

    if ((len > 1) && (optionName[1] == 'k') &&
	    (strncmp(optionName, "-keepalive", len) == 0)) {
	BOOL boolVar;
	int rtn;

    TcpState *statePtr = (TcpState *)instanceData;
    char host[NI_MAXHOST], port[NI_MAXSERV];
    SOCKET sock;
    size_t len = 0;
    int reverseDNS = 0;
#define SUPPRESS_RDNS_VAR "::tcl::unsupported::noReverseDNS"

    /*
     * 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_SetObjResult(interp, Tcl_NewStringObj(
		    "winsock is not initialized", -1));
	}
	return TCL_ERROR;
    }

    /*
     * Go one step in async connect
     *
     * If any error is thrown save it as backround error to report eventually
     * below.
     */

				 * connect. */
{
    TcpState *statePtr;
    const char *errorMsg = NULL;
    struct addrinfo *addrlist = NULL, *myaddrlist = NULL;
    char channelName[SOCK_CHAN_LENGTH];

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

    /*
     * 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;
    }

    /*
     * Do the name lookups for the local and remote addresses.
     */

    if (!TclCreateSocketAddress(interp, &addrlist, host, port, 0, &errorMsg)
            || !TclCreateSocketAddress(interp, &myaddrlist, myaddr, myport, 1,

Tcl_MakeTcpClientChannel(
    void *sock)		/* The socket to wrap up into a channel. */
{
    TcpState *statePtr;
    char channelName[SOCK_CHAN_LENGTH];
    ThreadSpecificData *tsdPtr;

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

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

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

    struct addrinfo *addrPtr;	/* Socket address to listen on. */
    TcpState *statePtr = NULL;	/* The returned value. */
    char channelName[SOCK_CHAN_LENGTH];
    u_long flag = 1;		/* Indicates nonblocking mode. */
    const char *errorMsg = NULL;
    int optvalue, port;

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

    /*
     * 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;
    }

    /*
     * Construct the addresses for each end of the socket.
     */

    if (TclSockGetPort(interp, service, "tcp", &port) != TCL_OK) {
	errorMsg = "invalid port number";

    /*
     * Wait for the thread to signal when the window has been created and if
     * it is ready to go.
     */

    WaitForSingleObject(tsdPtr->readyEvent, INFINITE);

    if (tsdPtr->hwnd == NULL) {
	goto initFailure;	/* Trouble creating the window. */
    }

    Tcl_CreateEventSource(SocketSetupProc, SocketCheckProc, NULL);
    return;

  initFailure:
    TclpFinalizeSockets();
    initialized = -1;
    return;
}

/*
 *----------------------------------------------------------------------
 *
 * SocketsEnabled --
 *
 *	Check that the WinSock was successfully initialized.
 *
 * Warning:
 *	This check was useful in times of Windows98 where WinSock may
 *	not be available. This is not the case any more.
 *	This function may be removed with TCL 9.0
 *
 * Results:
 *	1 if it is.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static int
SocketsEnabled(void)
{
    int enabled;

    Tcl_MutexLock(&socketMutex);
    enabled = (initialized == 1);
    Tcl_MutexUnlock(&socketMutex);
    return enabled;
}


/*
 *----------------------------------------------------------------------
 *
 * SocketExitHandler --
 *
 *	Callback invoked during exit clean up to delete the socket

    if (action == TCL_CHANNEL_THREAD_INSERT) {
	/*
	 * Ensure that socket subsystem is initialized in this thread, or else
	 * sockets will not work.
	 */

	Tcl_MutexLock(&socketMutex);
	InitSockets();
	Tcl_MutexUnlock(&socketMutex);

	tsdPtr = TCL_TSD_INIT(&dataKey);

	WaitForSingleObject(tsdPtr->socketListLock, INFINITE);
	statePtr->nextPtr = tsdPtr->socketList;
	tsdPtr->socketList = statePtr;