Further experimental follow-up: Add internal function TclOpenTcpClientEx(), as companion to Tcl_OpenTcpServerEx(). Should be exported through new TIP.

generic/tclIOCmd.c

@@ -1492,10 +1492,10 @@ Tcl_SocketObjCmd(
 	SKT_ASYNC, SKT_MYADDR, SKT_MYPORT, SKT_REUSEADDR, SKT_REUSEPORT,
 	SKT_SERVER
     };
-    int optionIndex, a, server = 0, myport = 0, async = 0, reusep = -1,
+    int optionIndex, a, server = 0, async = 0, reusep = -1,
 	reusea = -1;
     unsigned int flags = 0;
-    const char *host, *port, *myaddr = NULL;
+    const char *host, *port, *myaddr = NULL, *myport = NULL;
     Tcl_Obj *script = NULL;
     Tcl_Channel chan;
 
@@ -1532,18 +1532,13 @@ Tcl_SocketObjCmd(
 	    myaddr = TclGetString(objv[a]);
 	    break;
 	case SKT_MYPORT: {
-	    const char *myPortName;
-
 	    a++;
 	    if (a >= objc) {
 		Tcl_SetObjResult(interp, Tcl_NewStringObj(
 			"no argument given for -myport option", -1));
 		return TCL_ERROR;
 	    }
-	    myPortName = TclGetString(objv[a]);
-	    if (TclSockGetPort(interp, myPortName, "tcp", &myport) != TCL_OK) {
-		return TCL_ERROR;
-	    }
+	    myport = TclGetString(objv[a]);
 	    break;
 	}
 	case SKT_SERVER:
@@ -1670,13 +1665,7 @@ Tcl_SocketObjCmd(
 
 	Tcl_CreateCloseHandler(chan, TcpServerCloseProc, acceptCallbackPtr);
     } else {
-	int portNum;
-
-	if (TclSockGetPort(interp, port, "tcp", &portNum) != TCL_OK) {
-	    return TCL_ERROR;
-	}
-
-	chan = Tcl_OpenTcpClient(interp, portNum, host, myaddr, myport, async);
+	chan = TclOpenTcpClientEx(interp, port, host, myaddr, myport, async);
 	if (chan == NULL) {
 	    return TCL_ERROR;
 	}

generic/tclIOSock.c

@@ -158,7 +158,7 @@ TclCreateSocketAddress(
 				 * family */
     struct addrinfo **addrlist,	/* Socket address list */
     const char *host,		/* Host. NULL implies INADDR_ANY */
-    int port,			/* Port number */
+    const char *service,	/* Service */
     int willBind,		/* Is this an address to bind() to or to
 				 * connect() to? */
     const char **errorMsgPtr)	/* Place to store the error message detail, if
@@ -168,7 +168,7 @@ TclCreateSocketAddress(
     struct addrinfo *p;
     struct addrinfo *v4head = NULL, *v4ptr = NULL;
     struct addrinfo *v6head = NULL, *v6ptr = NULL;
-    char *native = NULL, portbuf[TCL_INTEGER_SPACE], *portstring;
+    char *native = NULL;
     const char *family = NULL;
     Tcl_DString ds;
     int result;
@@ -182,11 +182,8 @@ TclCreateSocketAddress(
      * when the loopback device is the only available network interface.
      */
 
-    if (host != NULL && port == 0) {
-	portstring = NULL;
-    } else {
-	TclFormatInt(portbuf, port);
-	portstring = portbuf;
+    if (host != NULL && service != NULL && !strcmp(service, "0")) {
+       service = NULL;
     }
 
     (void) memset(&hints, 0, sizeof(hints));
@@ -231,7 +228,7 @@ TclCreateSocketAddress(
 	hints.ai_flags |= AI_PASSIVE;
     }
 
-    result = getaddrinfo(native, portstring, &hints, addrlist);
+    result = getaddrinfo(native, service, &hints, addrlist);
 
     if (host != NULL) {
 	Tcl_DStringFree(&ds);

generic/tclInt.h

@@ -3068,8 +3068,12 @@ MODULE_SCOPE void	TclpFinalizePipes(void);
 MODULE_SCOPE void	TclpFinalizeSockets(void);
 MODULE_SCOPE int	TclCreateSocketAddress(Tcl_Interp *interp,
 			    struct addrinfo **addrlist,
-			    const char *host, int port, int willBind,
+			    const char *host, const char *service, int willBind,
 			    const char **errorMsgPtr);
+Tcl_Channel		TclOpenTcpClientEx(Tcl_Interp *interp,
+			    const char *service, const char *host,
+			    const char *myaddr,	const char *myservice,
+			    unsigned int flags);
 MODULE_SCOPE int	TclpThreadCreate(Tcl_ThreadId *idPtr,
 			    Tcl_ThreadCreateProc *proc, ClientData clientData,
 			    int stackSize, int flags);

unix/tclUnixSock.c

@@ -1282,18 +1282,33 @@ Tcl_OpenTcpClient(
     int async)			/* If nonzero, attempt to do an asynchronous
 				 * connect. Otherwise we do a blocking
 				 * connect. */
+{
+    char service[TCL_INTEGER_SPACE], myservice[TCL_INTEGER_SPACE];
+
+    TclFormatInt(service, port);
+    TclFormatInt(myservice, myport);
+
+    return TclOpenTcpClientEx(interp, service, host, myaddr, myservice, async!=0);
+}
+
+Tcl_Channel
+TclOpenTcpClientEx(
+    Tcl_Interp *interp,		/* For error reporting; can be NULL. */
+    const char *service,	/* Port number to open. */
+    const char *host,		/* Host on which to open port. */
+    const char *myaddr,		/* Client-side address */
+    const char *myservice,	/* Client-side port */
+    unsigned int flags)		/* If nonzero, attempt to do an asynchronous
+				 * connect. Otherwise we do a blocking
+				 * connect. */
 {
     TcpState *statePtr;
     const char *errorMsg = NULL;
     struct addrinfo *addrlist = NULL, *myaddrlist = NULL;
     char channelName[SOCK_CHAN_LENGTH];
 
-    /*
-     * Do the name lookups for the local and remote addresses.
-     */
-
-    if (!TclCreateSocketAddress(interp, &addrlist, host, port, 0, &errorMsg)
-            || !TclCreateSocketAddress(interp, &myaddrlist, myaddr, myport, 1,
+    if (!TclCreateSocketAddress(interp, &addrlist, host, service, 0, &errorMsg)
+            || !TclCreateSocketAddress(interp, &myaddrlist, myaddr, myservice, 1,
                     &errorMsg)) {
         if (addrlist != NULL) {
             freeaddrinfo(addrlist);
@@ -1310,7 +1325,7 @@ Tcl_OpenTcpClient(
      */
     statePtr = ckalloc(sizeof(TcpState));
     memset(statePtr, 0, sizeof(TcpState));
-    statePtr->flags = async ? TCP_ASYNC_CONNECT : 0;
+    statePtr->flags = (flags&1) ? TCP_ASYNC_CONNECT : 0;
     statePtr->cachedBlocking = TCL_MODE_BLOCKING;
     statePtr->addrlist = addrlist;
     statePtr->myaddrlist = myaddrlist;
@@ -1481,7 +1496,7 @@ Tcl_OpenTcpServerEx(
 	goto error;
     }
 
-    if (!TclCreateSocketAddress(interp, &addrlist, myHost, port, 1, &errorMsg)) {
+    if (!TclCreateSocketAddress(interp, &addrlist, myHost, service, 1, &errorMsg)) {
 	my_errno = errno;
 	goto error;
     }

win/tclWinSock.c

@@ -1873,7 +1873,7 @@ out:
 /*
  *----------------------------------------------------------------------
  *
- * Tcl_OpenTcpClient --
+ * Tcl_OpenTcpClient, TclOpenTcpClientEx --
  *
  *	Opens a TCP client socket and creates a channel around it.
  *
@@ -1897,6 +1897,25 @@ Tcl_OpenTcpClient(
     int async)			/* If nonzero, attempt to do an asynchronous
 				 * connect. Otherwise we do a blocking
 				 * connect. */
+{
+    char service[TCL_INTEGER_SPACE], myservice[TCL_INTEGER_SPACE];
+
+    TclFormatInt(service, port);
+    TclFormatInt(myservice, myport);
+
+    return TclOpenTcpClientEx(interp, service, host, myaddr, myservice, async!=0);
+}
+
+Tcl_Channel
+TclOpenTcpClientEx(
+    Tcl_Interp *interp,		/* For error reporting; can be NULL. */
+    const char *service,	/* Port number to open. */
+    const char *host,		/* Host on which to open port. */
+    const char *myaddr,		/* Client-side address */
+    const char *myservice,	/* Client-side port */
+    unsigned int flags)		/* If nonzero, attempt to do an asynchronous
+				 * connect. Otherwise we do a blocking
+				 * connect. */
 {
     TcpState *statePtr;
     const char *errorMsg = NULL;
@@ -1921,8 +1940,8 @@ Tcl_OpenTcpClient(
      * Do the name lookups for the local and remote addresses.
      */
 
-    if (!TclCreateSocketAddress(interp, &addrlist, host, port, 0, &errorMsg)
-            || !TclCreateSocketAddress(interp, &myaddrlist, myaddr, myport, 1,
+    if (!TclCreateSocketAddress(interp, &addrlist, host, service, 0, &errorMsg)
+            || !TclCreateSocketAddress(interp, &myaddrlist, myaddr, myservice, 1,
                     &errorMsg)) {
         if (addrlist != NULL) {
             freeaddrinfo(addrlist);
@@ -1937,7 +1956,7 @@ Tcl_OpenTcpClient(
     statePtr = NewSocketInfo(INVALID_SOCKET);
     statePtr->addrlist = addrlist;
     statePtr->myaddrlist = myaddrlist;
-    if (async) {
+    if (flags&1) {
 	statePtr->flags |= TCP_ASYNC_CONNECT;
     }
 
@@ -2078,7 +2097,7 @@ Tcl_OpenTcpServerEx(
 	goto error;
     }
 
-    if (!TclCreateSocketAddress(interp, &addrlist, myHost, port, 1, &errorMsg)) {
+    if (!TclCreateSocketAddress(interp, &addrlist, myHost, service, 1, &errorMsg)) {
 	goto error;
     }