patch 9.1.1651: Cannot use clientserver over socket

Problem:  Cannot use clientserver over Unix domain socket
Solution: Implement socketserver functionality (Foxe Chen).

fixes: #3509
closes: #17839

Signed-off-by: Foxe Chen <chen.foxe@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

.github/workflows/ci.yml

@@ -85,6 +85,12 @@ jobs:
           - features: normal
             compiler: gcc
             extra: [vimtags]
+          - features: huge
+            compiler: gcc
+            extra: [no_x11]
+          - features: huge
+            compiler: gcc
+            extra: [socketserver]
 
     steps:
       - name: Checkout repository from github
@@ -220,7 +226,7 @@ jobs:
           tiny)
             echo "TEST=testtiny"
             if ${{ contains(matrix.extra, 'nogui') }}; then
-              echo "CONFOPT=--disable-gui"
+              CONFOPT="--disable-gui"
             fi
             ;;
           normal)
@@ -232,10 +238,16 @@ jobs:
               PYTHON3_CONFOPT="--with-python3-stable-abi=3.8"
             fi
             # The ubuntu-24.04 CI runner does not provide a python2 package.
-            echo "CONFOPT=--enable-perlinterp=${INTERFACE} --enable-pythoninterp=no --enable-python3interp=${INTERFACE} --enable-rubyinterp=${INTERFACE} --enable-luainterp=${INTERFACE} --enable-tclinterp=${INTERFACE} ${PYTHON3_CONFOPT}"
+            CONFOPT="--enable-perlinterp=${INTERFACE} --enable-pythoninterp=no --enable-python3interp=${INTERFACE} --enable-rubyinterp=${INTERFACE} --enable-luainterp=${INTERFACE} --enable-tclinterp=${INTERFACE} ${PYTHON3_CONFOPT}"
             ;;
           esac
 
+          if ${{ contains(matrix.extra, 'no_x11') }}; then
+            CONFOPT="${CONFOPT} --without-x --disable-gui"
+          fi
+          if ${{ contains(matrix.extra, 'socketserver') }}; then
+            CONFOPT="${CONFOPT} --enable-socketserver"
+          fi
           if ${{ matrix.coverage == true }}; then
             CFLAGS="${CFLAGS} --coverage -DUSE_GCOV_FLUSH"
             echo "LDFLAGS=--coverage"
@@ -259,6 +271,7 @@ jobs:
             echo "TEST=-C runtime/doc vimtags VIMEXE=../../${SRCDIR}/vim"
           fi
           echo "CFLAGS=${CFLAGS}"
+          echo "CONFOPT=${CONFOPT}"
           # Disables GTK attempt to integrate with the accessibility service that does run in CI.
           echo "NO_AT_BRIDGE=1"
           ) >> $GITHUB_ENV

runtime/doc/builtin.txt

@@ -13046,6 +13046,7 @@ scrollbind		Compiled with 'scrollbind' support. (always true)
 showcmd			Compiled with 'showcmd' support.
 signs			Compiled with |:sign| support.
 smartindent		Compiled with 'smartindent' support. (always true)
+socketserver		Compiled with socket server functionality. (Unix only)
 sodium			Compiled with libsodium for better crypt support
 sound			Compiled with sound support, e.g. `sound_playevent()`
 spell			Compiled with spell checking support |spell|.

runtime/doc/remote.txt

@@ -1,4 +1,4 @@
-*remote.txt*    For Vim version 9.1.  Last change: 2022 Feb 17
+*remote.txt*    For Vim version 9.1.  Last change: 2025 Aug 18
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -61,7 +61,10 @@ The following command line arguments are available:
    --servername {name}		Become the server {name}.  When used together
 				with one of the --remote commands: connect to
 				server {name} instead of the default (see
-				below).  The name used will be uppercase.
+				below).  The name used will be uppercase.  If
+				using the socketserver, you can specify a
+				path, see |socketserver-name| for more
+				details.
 								*--remote-send*
    --remote-send {keys}		Send {keys} to server and exit.  The {keys}
 				are not mapped.  Special key names are
@@ -72,6 +75,12 @@ The following command line arguments are available:
 				on stdout.
 								*--serverlist*
    --serverlist			Output a list of server names.
+								*--clientserver*
+   --clientserver {method}	Use the specified method {method} as the
+				backend for clientserver functionality. Can
+				either be "socket" or "x11".
+				{only available when Vim is compiled with both
+				|+X11| and |+socketserver| features}
 
 
 Examples ~
@@ -105,7 +114,8 @@ specified name is not available, a postfix is applied until a free name is
 encountered, i.e. "gvim1" for the second invocation of gvim on a particular
 X-server.  The resulting name is available in the servername builtin variable
 |v:servername|.  The case of the server name is ignored, thus "gvim" and
-"GVIM" are considered equal.
+"GVIM" are considered equal.  Note if a socket server is being used, there are
+some differences, see |socketserver-differences|.
 
 When Vim is invoked with --remote, --remote-wait or --remote-send it will try
 to locate the server name determined by the invocation name and --servername
@@ -119,7 +129,8 @@ itself.  This way it is not necessary to know whether gvim is already started
 when sending command to it.
 
 The --serverlist argument will cause Vim to print a list of registered command
-servers on the standard output (stdout) and exit.
+servers on the standard output (stdout) and exit.  If a socket server is being
+used, there are caveats, see |socketserver-differences|.
 							*{server}*
 The {server} argument is used by several functions.  When this is an empty
 string then on Unix the default server name is used, which is "GVIM".  On
@@ -206,4 +217,64 @@ When using gvim, the --remote-wait only works properly this way: >
 
 	start /w gvim --remote-wait file.txt
 <
+==============================================================================
+3. Socket server specific items			    *socketserver-clientserver*
+				    *E1563* *E1564* *E1565* *E1566* *E1567*
+
+The communication between client and server is done using Unix domain sockets.
+These sockets are either placed in these directories in the following order of
+availability:
+    1. "$XDG_RUTIME_DIR/vim" if $XDG_RUNTIME_DIR is set in the environment.
+    2. "$TMPDIR/vim-[uid]", where "[uid]" is the uid of the user. This
+       directory will have the access permissions set to 700 so only the user
+       can read or write from/to it. If $TMPDIR is not set, "/tmp" is used.
+
+						    *socketserver-name*
+When specifying the server id/name, it can be taken as a generic name or an
+absolute or relative path.  If the server id starts with either a "/"
+(absolute) or "./" | "../" (relative), then it is taken as path to the socket.
+Otherwise the server id will be the filename of the socket which will be
+placed in the above common directories.  Note that a server id/name can only
+contain slashes "/" if it is taken as a path, so names such as "abc/dir" will
+be invalid.
+
+Socket server functionality is available in both GTK GUI and terminal versions of
+Vim.  Unless Vim is compiled with |+autoservername| feature, the socket server
+will have to started explicitly, just like X11, even in the GUI.
+
+If Vim crashes or does not exit cleanly, the socket server will not remove the
+socket file and it will be left around.  This is generally not a problem,
+because if a socket name is taken, Vim checks if the socket in its place is
+dead (not attached to any process), and can replace it instead of finding a
+new name.
+
+To send commands to a Vim socket server from another application, read the
+source file src/os_unix.c, there is detailed description of the protocol used.
+
+						    *socketserver-differences*
+Most of the functionality is the same as X11, however unlike X11, where the
+client does not need to be a server in order to communicate with another
+server, the socket server requires the server to be running even as a client.
+The exception is |serverlist()| or the |--serverlist| argument, which does not
+require the server to be running.
+
+Additionally, the server id or client id will not be a number like X11 or
+MS-Windows (shown in hex representation), instead it is the absolute path to
+the socket.  This can be seen via the |v:servername| variable.
+
+The |--serverlist| argument will act just like X11, however it only checks the
+given common directories above.  If a custom path is used for a socket, it
+will not be detected, such as a path either not in $XDG_RUNTIME_DIR or
+<$TMPDIR or /tmp>/vim of the |--serverlist| Vim process.
+
+If you have both |+socketserver| and |+X11| compiled, you will need to add
+|--clientserver| set to "socket" in combination with |--serverlist| to list
+the available servers.  You cannot list both types of backends in one command.
+
+						    *socketserver-x11*
+If Vim is compiled with both |+X11| and |+socketserver|, then deciding which
+backend to use is done at startup time, via the |--clientserver| argument.  By
+default if it is not specified, then X11 will be used.  A Vim instance using a
+socket server cannot communicate with one using X11.
+
  vim:tw=78:sw=4:ts=8:noet:ft=help:norl:

runtime/doc/tags

@@ -1497,6 +1497,7 @@ $quote	eval.txt	/*$quote*
 +scrollbind	various.txt	/*+scrollbind*
 +signs	various.txt	/*+signs*
 +smartindent	various.txt	/*+smartindent*
++socketserver	various.txt	/*+socketserver*
 +sodium	various.txt	/*+sodium*
 +sound	various.txt	/*+sound*
 +spell	various.txt	/*+spell*
@@ -1557,6 +1558,7 @@ $quote	eval.txt	/*$quote*
 --	starting.txt	/*--*
 ---	starting.txt	/*---*
 --clean	starting.txt	/*--clean*
+--clientserver	remote.txt	/*--clientserver*
 --cmd	starting.txt	/*--cmd*
 --echo-wid	starting.txt	/*--echo-wid*
 --gui-dialog-file	starting.txt	/*--gui-dialog-file*
@@ -4697,6 +4699,11 @@ E156	sign.txt	/*E156*
 E1560	vim9.txt	/*E1560*
 E1561	vim9.txt	/*E1561*
 E1562	options.txt	/*E1562*
+E1563	remote.txt	/*E1563*
+E1564	remote.txt	/*E1564*
+E1565	remote.txt	/*E1565*
+E1566	remote.txt	/*E1566*
+E1567	remote.txt	/*E1567*
 E157	sign.txt	/*E157*
 E158	sign.txt	/*E158*
 E159	sign.txt	/*E159*
@@ -10225,6 +10232,10 @@ slow-fast-terminal	term.txt	/*slow-fast-terminal*
 slow-start	starting.txt	/*slow-start*
 slow-terminal	term.txt	/*slow-terminal*
 socket-interface	channel.txt	/*socket-interface*
+socketserver-clientserver	remote.txt	/*socketserver-clientserver*
+socketserver-differences	remote.txt	/*socketserver-differences*
+socketserver-name	remote.txt	/*socketserver-name*
+socketserver-x11	remote.txt	/*socketserver-x11*
 sort()	builtin.txt	/*sort()*
 sorting	change.txt	/*sorting*
 sound-functions	usr_41.txt	/*sound-functions*

runtime/doc/various.txt

@@ -1,4 +1,4 @@
-*various.txt*   For Vim version 9.1.  Last change: 2025 Aug 06
+*various.txt*   For Vim version 9.1.  Last change: 2025 Aug 18
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -487,6 +487,8 @@ m  *+ruby/dyn*		Ruby interface |ruby-dynamic| |/dyn|
 T  *+scrollbind*	'scrollbind'
 N  *+signs*		|:sign|
 T  *+smartindent*	'smartindent'
+N  *+socketserver*	Unix only: socket server backend for clientserver
+			functionality
 H  *+sodium*		compiled with libsodium for better encryption support
 H  *+sound*		|sound_playevent()|, |sound_playfile()| functions, etc.
 N  *+spell*		spell checking support, see |spell|

runtime/doc/version9.txt

@@ -41745,6 +41745,10 @@ Others: ~
   Unicode 16.
 - Two additional digraphs have been added: LEFT ANGLE BRACKET "<[" and RIGHT
   ANGLE BRACKET "]>".
+- Support for Unix domain sockets have been added for the clientserver
+  feature, see |socketserver-clientserver|.
+
+Platform specific ~
 - MS-Winodws: Paths like "\Windows" and "/Windows" are now considered to be
   absolute paths (to the current drive) and no longer relative.
 
@@ -41849,6 +41853,7 @@ Options: ~
 
 Vim Arguments: ~
 |-Y|			Do not connect to the Wayland compositor.
+|--clientserver|	Specify backend  for clientserver functionality.
 
 
 ==============================================================================

runtime/doc/vim.1

@@ -499,7 +499,14 @@ List the names of all Vim servers that can be found.
 .TP
 \-\-servername {name}
 Use {name} as the server name.  Used for the current Vim, unless used with a
-\-\-remote argument, then it's the name of the server to connect to.
+\-\-remote argument, then it's the name of the server to connect to.  If the
+socketserver backend is being used, if the name starts with "/", "./", or "../",
+it is taken as either an absolute, relative or relative path to the socket.
+.TP
+\-\-clientserver {backend}
+Use {backend} as the backend for clientserver functionality, either "socket" or
+"x11" respectively.  Only available when compiled with both socketserver and X11
+features present
 .TP
 \-\-socketid {id}
 GTK GUI only: Use the GtkPlug mechanism to run gVim in another window.

runtime/doc/vim.man

@@ -378,7 +378,16 @@ OPTIONS
        --servername {name}
                    Use  {name}  as the server name.  Used for the current Vim,
                    unless used with a --remote argument, then it's the name of
-                   the server to connect to.
+                   the server to connect to.  If the socketserver  backend  is
+                   being used, if the name starts with "/", "./", or "../", it
+                   is  taken  as either an absolute, relative or relative path
+                   to the socket.
+
+       --clientserver {backend}
+                   Use {backend} as the backend for  clientserver  functional‐
+                   ity, either "socket" or "x11" respectively.  Only available
+                   when  compiled  with  both  socketserver  and  X11 features
+                   present
 
        --socketid {id}
                    GTK GUI only: Use the GtkPlug mechanism to run gVim in  an‐

runtime/plugin/rrhelper.vim

@@ -16,9 +16,10 @@ function SetupRemoteReplies()
   let max = argc()
 
   let id = expand("<client>")
-  if id == 0
+  if (type(id) == v:t_number && id == 0) || (type(id) == v:t_string && id == '')
     return
   endif
+
   while cnt < max
     " Handle same file from more clients and file being more than once
     " on the command line by encoding this stuff in the group name

runtime/syntax/vim.vim

@@ -2,7 +2,7 @@
 " Language:	   Vim script
 " Maintainer:	   Hirohito Higashi <h.east.727 ATMARK gmail.com>
 "	   Doug Kearns <dougkearns@gmail.com>
-" Last Change:	   2025 Aug 16
+" Last Change:	   2025 Aug 18
 " Former Maintainer: Charles E. Campbell
 
 " DO NOT CHANGE DIRECTLY.

src/auto/configure

@@ -854,6 +854,7 @@ enable_netbeans
 enable_channel
 enable_terminal
 enable_autoservername
+enable_socketserver
 enable_multibyte
 enable_rightleft
 enable_arabic
@@ -1534,6 +1535,7 @@ Optional Features:
   --disable-channel       Disable process communication support.
   --enable-terminal       Enable terminal emulation support.
   --enable-autoservername Automatically define servername at vim startup.
+  --enable-socketserver Use sockets for clientserver communication.
   --enable-multibyte      Include multibyte editing support.
   --disable-rightleft     Do not include Right-to-Left language support.
   --disable-arabic        Do not include Arabic language support.
@@ -9084,6 +9086,40 @@ if test "$enable_autoservername" = "yes"; then
 
 fi
 
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking --enable-socketserver argument" >&5
+printf %s "checking --enable-socketserver argument... " >&6; }
+# Check whether --enable-socketserver was given.
+if test ${enable_socketserver+y}
+then :
+  enableval=$enable_socketserver; enable_socketserver=$enableval
+else case e in #(
+  e) if test "x$features" = xtiny
+then :
+  enable_socketserver=no_auto
+			 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: cannot use socketserver with tiny features" >&5
+printf "%s\n" "cannot use socketserver with tiny features" >&6; }
+else case e in #(
+  e) enable_socketserver=auto ;;
+esac
+fi ;;
+esac
+fi
+
+if test "$enable_socketserver" = "yes"; then
+  printf "%s\n" "#define WANT_SOCKETSERVER 1" >>confdefs.h
+
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+printf "%s\n" "yes" >&6; }
+elif test "$enable_socketserver" = "auto"; then
+  printf "%s\n" "#define MAYBE_SOCKETSERVER 1" >>confdefs.h
+
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: auto" >&5
+printf "%s\n" "auto" >&6; }
+elif test "$enable_socketserver" = "no"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+fi
+
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking --enable-multibyte argument" >&5
 printf %s "checking --enable-multibyte argument... " >&6; }
 # Check whether --enable-multibyte was given.

src/clientserver.c

@@ -15,6 +15,11 @@
 
 #if defined(FEAT_CLIENTSERVER) || defined(PROTO)
 
+#ifdef FEAT_SOCKETSERVER
+# include <sys/socket.h>
+# include "sys/un.h"
+#endif
+
 static void cmdsrv_main(int *argc, char **argv, char_u *serverName_arg, char_u **serverStr);
 static char_u *serverMakeName(char_u *arg, char *cmd);
 
@@ -191,6 +196,8 @@ static char_u *build_drop_cmd(int filec, char **filev, int tabs, int sendReply);
     void
 exec_on_server(mparm_T *parmp)
 {
+    int made_name = FALSE;
+
     if (parmp->serverName_arg != NULL && *parmp->serverName_arg == NUL)
 	return;
 
@@ -199,6 +206,23 @@ exec_on_server(mparm_T *parmp)
     serverInitMessaging();
 # endif
 
+#ifdef FEAT_SOCKETSERVER
+    // If servername is specified and we are using sockets, always init the
+    // sockt server. We may need to receive replies back to us. If --serverlist
+    // is passed, the socket server will be uninitialized before listing
+    // sockets then initialized after. This is so we don't add our own socket
+    // in the list. This does not happen in serverlist().
+    if ((parmp->serverArg || parmp->serverName_arg != NULL) &&
+	    clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+    {
+	parmp->servername = serverMakeName(parmp->serverName_arg,
+		parmp->argv[0]);
+	if (socket_server_init(parmp->servername) == OK)
+	    TIME_MSG("initialize socket server");
+	made_name = TRUE;
+    }
+#endif
+
     /*
      * When a command server argument was found, execute it.  This may
      * exit Vim when it was successful.  Otherwise it's executed further
@@ -214,8 +238,9 @@ exec_on_server(mparm_T *parmp)
     // If we're still running, get the name to register ourselves.
     // On Win32 can register right now, for X11 need to setup the
     // clipboard first, it's further down.
-    parmp->servername = serverMakeName(parmp->serverName_arg,
+    if (!made_name && parmp->servername == NULL)
-	    parmp->argv[0]);
+	parmp->servername = serverMakeName(parmp->serverName_arg,
+		parmp->argv[0]);
 # ifdef MSWIN
     if (parmp->servername != NULL)
     {
@@ -224,14 +249,13 @@ exec_on_server(mparm_T *parmp)
     }
 # endif
 }
-
 /*
  * Prepare for running as a Vim server.
  */
     void
 prepare_server(mparm_T *parmp)
 {
-# if defined(FEAT_X11)
+# if defined(FEAT_X11) || defined(FEAT_SOCKETSERVER)
     /*
      * Register for remote command execution with :serversend and --remote
      * unless there was a -X or a --servername '' on the command line.
@@ -239,7 +263,13 @@ prepare_server(mparm_T *parmp)
      * or when compiling with autoservername.
      * When running as root --servername is also required.
      */
-    if (X_DISPLAY != NULL && parmp->servername != NULL && (
+
+    if (
+#  ifdef FEAT_X11
+	    X_DISPLAY != NULL &&
+#  endif
+
+	    parmp->servername != NULL && (
 #  if defined(FEAT_AUTOSERVERNAME) || defined(FEAT_GUI)
 		(
 #   if defined(FEAT_AUTOSERVERNAME)
@@ -254,12 +284,26 @@ prepare_server(mparm_T *parmp)
 #  endif
 		parmp->serverName_arg != NULL))
     {
-	(void)serverRegisterName(X_DISPLAY, parmp->servername);
+#  ifdef FEAT_SOCKETSERVER
+	if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+	{
+	    if (socket_server_init(parmp->servername) == OK)
+		TIME_MSG("initialize socket server");
+	}
+#  endif
+#  ifdef FEAT_X11
+	if (clientserver_method == CLIENTSERVER_METHOD_X11)
+	{
+	    (void)serverRegisterName(X_DISPLAY, parmp->servername);
+	    TIME_MSG("register x11 server name");
+	}
+#  endif
 	vim_free(parmp->servername);
-	TIME_MSG("register server name");
     }
+#ifdef FEAT_X11
     else
 	serverDelayedStartName = parmp->servername;
+#endif
 # endif
 
     /*
@@ -299,9 +343,12 @@ cmdsrv_main(
 #define ARGTYPE_SEND		3
     int		silent = FALSE;
     int		tabs = FALSE;
-# ifndef FEAT_X11
+#ifdef FEAT_SOCKETSERVER
+    char_u	*receiver;
+#endif
+# ifdef MSWIN
     HWND	srv;
-# else
+# elif defined(FEAT_X11)
     Window	srv;
 
     setup_term_clip();
@@ -384,16 +431,27 @@ cmdsrv_main(
 		}
 		Argc = i;
 	    }
-# ifdef FEAT_X11
+
-	    if (xterm_dpy == NULL)
+#ifdef FEAT_SOCKETSERVER
+	    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+		ret = socket_server_send(
+			sname, *serverStr, NULL, &receiver,
+			0, -1, silent);
+#endif
+#ifdef FEAT_X11
+	    if (clientserver_method == CLIENTSERVER_METHOD_X11)
 	    {
-		mch_errmsg(_("No display"));
+		if (xterm_dpy == NULL)
-		ret = -1;
+		{
+		    mch_errmsg(_("No display"));
+		    ret = -1;
+		}
+		else
+		    ret = serverSendToVim(xterm_dpy, sname, *serverStr,
+			    NULL, &srv, 0, 0, 0, silent);
 	    }
-	    else
+#endif
-		ret = serverSendToVim(xterm_dpy, sname, *serverStr,
+#ifdef MSWIN
-						  NULL, &srv, 0, 0, 0, silent);
-# else
 	    // Win32 always works?
 	    ret = serverSendToVim(sname, *serverStr, NULL, &srv, 0, 0, silent);
 # endif
@@ -452,14 +510,24 @@ cmdsrv_main(
 		vim_memset(done, 0, numFiles);
 		while (memchr(done, 0, numFiles) != NULL)
 		{
-		    char_u  *p;
+		    char_u  *p = NULL;
 		    int	    j;
 # ifdef MSWIN
 		    p = serverGetReply(srv, NULL, TRUE, TRUE, 0);
 		    if (p == NULL)
 			break;
 # else
-		    if (serverReadReply(xterm_dpy, srv, &p, TRUE, -1) < 0)
+#  ifdef FEAT_SOCKETSERVER
+		    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET
+			    && socket_server_read_reply(receiver, &p, -1) == FAIL)
+			    break;
+#  endif
+#  ifdef FEAT_X11
+		    if (clientserver_method == CLIENTSERVER_METHOD_X11
+			    && serverReadReply(xterm_dpy, srv, &p, TRUE, -1) < 0)
+			    break;
+#   endif
+		    if (p == NULL)
 			break;
 # endif
 		    j = atoi((char *)p);
@@ -490,12 +558,34 @@ cmdsrv_main(
 	    if (serverSendToVim(sname, (char_u *)argv[i + 1],
 						  &res, NULL, 1, 0, FALSE) < 0)
 # else
-	    if (xterm_dpy == NULL)
+#  ifdef FEAT_SOCKETSERVER
-		mch_errmsg(_("No display: Send expression failed.\n"));
+	    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
-	    else if (serverSendToVim(xterm_dpy, sname, (char_u *)argv[i + 1],
+	    {
-					       &res, NULL, 1, 0, 1, FALSE) < 0)
+		if (!socket_server_valid())
+		    mch_errmsg(_("Socket server not online:"
+				"Send expression failed"));
+		else if (socket_server_send(sname, (char_u *)argv[i + 1],
+			    &res, NULL, 1, 0, FALSE) < 0)
+		    goto expr_fail;
+	    }
+#  endif
+#  ifdef FEAT_X11
+	    if (clientserver_method == CLIENTSERVER_METHOD_X11)
+	    {
+		if (xterm_dpy == NULL)
+		    mch_errmsg(_("No display: Send expression failed.\n"));
+		else if (serverSendToVim(xterm_dpy, sname,
+			    (char_u *)argv[i + 1], &res,
+			    NULL, 1, 0, 1, FALSE) < 0)
+		    goto expr_fail;
+	    }
+#  endif
+	    if (FALSE)
 # endif
 	    {
+# if !defined(MSWIN)
+expr_fail:
+# endif
 		if (res != NULL && *res != NUL)
 		{
 		    // Output error from remote
@@ -511,8 +601,25 @@ cmdsrv_main(
 	    // Win32 always works?
 	    res = serverGetVimNames();
 # else
-	    if (xterm_dpy != NULL)
+#  ifdef FEAT_SOCKETSERVER
+	    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+	    {
+		int was_init = socket_server_valid();
+
+		// Don't want to add ourselves to the list. So shutdown the
+		// server before listing then startup back again.
+		socket_server_uninit();
+		res = socket_server_list_sockets();
+
+		if (was_init)
+		    socket_server_init(NULL);
+	    }
+#  endif
+#  ifdef FEAT_X11
+	    if (clientserver_method == CLIENTSERVER_METHOD_X11 &&
+		    xterm_dpy != NULL)
 		res = serverGetVimNames(xterm_dpy);
+#  endif
 # endif
 	    if (did_emsg)
 		mch_errmsg("\n");
@@ -541,6 +648,9 @@ cmdsrv_main(
 
     if (didone)
     {
+#ifdef FEAT_SOCKETSERVER
+	socket_server_uninit();
+#endif
 	display_errors();	// display any collected messages
 	exit(exiterr);	// Mission accomplished - get out
     }
@@ -694,7 +804,24 @@ serverMakeName(char_u *arg, char *cmd)
     char_u *p;
 
     if (arg != NULL && *arg != NUL)
+    {
+#ifdef FEAT_SOCKETSERVER
+	// If we are using a socket server, we want to preserve the original
+	// name if it is a path, else uppercase it if its just a generic name.
+	if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+	{
+	    if (arg[0] == '/' || STRNCMP(arg, "./", 2) == 0 ||
+		    STRNCMP(arg, "../", 3) == 0)
+		p = vim_strsave(arg);
+	    else
+		p = vim_strsave_up(arg);
+	}
+	else
+	    p = vim_strsave_up(arg);
+#else
 	p = vim_strsave_up(arg);
+#endif
+    }
     else
     {
 	p = vim_strsave_up(gettail((char_u *)cmd));
@@ -747,7 +874,12 @@ remote_common(typval_T *argvars, typval_T *rettv, int expr)
 # ifdef MSWIN
     HWND	w;
 # else
+#ifdef FEAT_X11
     Window	w;
+#endif
+#ifdef FEAT_SOCKETSERVER
+    char_u	*client = NULL;
+#endif
 # endif
 
     if (check_restricted() || check_secure())
@@ -768,14 +900,33 @@ remote_common(typval_T *argvars, typval_T *rettv, int expr)
 # ifdef MSWIN
     if (serverSendToVim(server_name, keys, &r, &w, expr, timeout, TRUE) < 0)
 # else
-    if (serverSendToVim(X_DISPLAY, server_name, keys, &r, &w, expr, timeout,
+#ifdef FEAT_SOCKETSERVER
-								  0, TRUE) < 0)
+    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+	if (socket_server_send(server_name, keys, &r, &client, expr,
+		    timeout * 1000, TRUE) < 0)
+	    goto stuff;
+#endif
+#ifdef FEAT_X11
+    if (clientserver_method == CLIENTSERVER_METHOD_X11)
+	if (serverSendToVim(X_DISPLAY, server_name, keys, &r, &w, expr, timeout,
+		    0, TRUE) < 0)
+	    goto stuff;
+#endif
 # endif
+#if !defined(MSWIN)
+    if (FALSE)
     {
+stuff:
+#else
+    {
+#endif
 	if (r != NULL)
 	{
 	    emsg((char *)r);	// sending worked but evaluation failed
 	    vim_free(r);
+#ifdef FEAT_SOCKETSERVER
+	    vim_free(client);
+#endif
 	}
 	else
 	    semsg(_(e_unable_to_send_to_str), server_name);
@@ -787,19 +938,39 @@ remote_common(typval_T *argvars, typval_T *rettv, int expr)
     if (argvars[2].v_type != VAR_UNKNOWN)
     {
 	dictitem_T	v;
+#if defined(FEAT_SOCKETSERVER)
+	struct sockaddr_un addr;
+	char_u		str[sizeof(addr.sun_path)];
+#else
 	char_u		str[30];
+#endif
 	char_u		*idvar;
 
 	idvar = tv_get_string_chk(&argvars[2]);
 	if (idvar != NULL && *idvar != NUL)
 	{
+#ifdef MSWIN
 	    sprintf((char *)str, PRINTF_HEX_LONG_U, (long_u)w);
+#else
+#ifdef FEAT_X11
+	    if (clientserver_method == CLIENTSERVER_METHOD_X11)
+		sprintf((char *)str, PRINTF_HEX_LONG_U, (long_u)w);
+#endif
+#ifdef FEAT_SOCKETSERVER
+	    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+		vim_snprintf((char *)str, sizeof(addr.sun_path),
+			"%s", client);
+#endif
+#endif
 	    v.di_tv.v_type = VAR_STRING;
 	    v.di_tv.vval.v_string = vim_strsave(str);
 	    set_var(idvar, &v.di_tv, FALSE);
 	    vim_free(v.di_tv.vval.v_string);
 	}
     }
+#ifdef FEAT_SOCKETSERVER
+    vim_free(client);
+#endif
 }
 #endif
 
@@ -890,11 +1061,20 @@ f_remote_peek(typval_T *argvars UNUSED, typval_T *rettv)
 	rettv->vval.v_number = (s != NULL);
     }
 # else
-    if (check_connection() == FAIL)
+#  ifdef FEAT_SOCKETSERVER
-	return;
+    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+	rettv->vval.v_number = socket_server_peek_reply(serverid, &s);
+#  endif
+#  ifdef FEAT_X11
+    if (clientserver_method == CLIENTSERVER_METHOD_X11)
+    {
+	if (check_connection() == FAIL)
+	    return;
 
-    rettv->vval.v_number = serverPeekReply(X_DISPLAY,
+	rettv->vval.v_number = serverPeekReply(X_DISPLAY,
-						serverStrToWin(serverid), &s);
+		serverStrToWin(serverid), &s);
+    }
+#  endif
 # endif
 
     if (argvars[1].v_type != VAR_UNKNOWN && rettv->vval.v_number > 0)
@@ -943,12 +1123,21 @@ f_remote_read(typval_T *argvars UNUSED, typval_T *rettv)
 	if (n != 0)
 	    r = serverGetReply((HWND)n, FALSE, TRUE, TRUE, timeout);
 	if (r == NULL)
-# else
-	if (check_connection() == FAIL
-		|| serverReadReply(X_DISPLAY, serverStrToWin(serverid),
-						       &r, FALSE, timeout) < 0)
-# endif
 	    emsg(_(e_unable_to_read_server_reply));
+# else
+#  ifdef FEAT_SOCKETSERVER
+	if (clientserver_method == CLIENTSERVER_METHOD_SOCKET &&
+		socket_server_read_reply(serverid, &r, timeout * 1000) == FAIL)
+	    emsg(_(e_unable_to_read_server_reply));
+#  endif
+#  ifdef FEAT_X11
+	if (clientserver_method == CLIENTSERVER_METHOD_X11 &&
+		(check_connection() == FAIL
+		|| serverReadReply(X_DISPLAY, serverStrToWin(serverid),
+						       &r, FALSE, timeout) < 0))
+	    emsg(_(e_unable_to_read_server_reply));
+#  endif
+# endif
     }
 #endif
     rettv->v_type = VAR_STRING;
@@ -992,11 +1181,18 @@ f_remote_startserver(typval_T *argvars UNUSED, typval_T *rettv UNUSED)
     }
 
     char_u *server = tv_get_string_chk(&argvars[0]);
-# ifdef FEAT_X11
+# ifdef MSWIN
-    if (check_connection() == OK)
-	serverRegisterName(X_DISPLAY, server);
-# else
     serverSetName(server);
+# else
+# ifdef FEAT_SOCKETSERVER
+    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+	socket_server_init(server);
+# endif
+# ifdef FEAT_X11
+    if (clientserver_method == CLIENTSERVER_METHOD_X11 &&
+	    check_connection() == OK)
+	serverRegisterName(X_DISPLAY, server);
+# endif
 # endif
 
 #else
@@ -1026,13 +1222,30 @@ f_server2client(typval_T *argvars UNUSED, typval_T *rettv)
     if (server == NULL || reply == NULL)
 	return;
 
-# ifdef FEAT_X11
+#ifdef FEAT_SOCKETSERVER
-    if (check_connection() == FAIL)
+    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET &&
-	return;
+	    socket_server_send_reply(server, reply) == FAIL)
-# endif
+	goto fail;
+#endif
 
+#ifdef FEAT_X11
+    if (clientserver_method == CLIENTSERVER_METHOD_X11 &&
+	    check_connection() == FAIL)
+	return;
+
+    if (clientserver_method == CLIENTSERVER_METHOD_X11 &&
+	    serverSendReply(server, reply) < 0)
+#endif
+#ifdef MSWIN
     if (serverSendReply(server, reply) < 0)
+#endif
+#if defined(FEAT_SOCKETSERVER) && !defined(FEAT_X11) && !defined(MSWIN)
+    if (FALSE)
+#endif
     {
+#ifdef FEAT_SOCKETSERVER
+fail:
+#endif
 	emsg(_(e_unable_to_send_to_client));
 	return;
     }
@@ -1051,9 +1264,18 @@ f_serverlist(typval_T *argvars UNUSED, typval_T *rettv)
 # ifdef MSWIN
     r = serverGetVimNames();
 # else
+#  ifdef FEAT_SOCKETSERVER
+    if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+	r = socket_server_list_sockets();
+#  endif
+#  ifdef FEAT_X11
+    if (clientserver_method == CLIENTSERVER_METHOD_X11)
+    {
     make_connection();
     if (X_DISPLAY != NULL)
 	r = serverGetVimNames(X_DISPLAY);
+    }
+#  endif
 # endif
 #endif
     rettv->v_type = VAR_STRING;

src/config.h.in

@@ -406,6 +406,12 @@
 /* Define if you want to always define a server name at vim startup. */
 #undef FEAT_AUTOSERVERNAME
 
+/* Define if you want to use sockets for clientserver communication. */
+#undef WANT_SOCKETSERVER
+
+/* Define if you want to use sockets for clientserver communication if it makes sense. */
+#undef MAYBE_SOCKETSERVER
+
 /* Define if you want to include fontset support. */
 #undef FEAT_XFONTSET
 

src/configure.ac

@@ -2340,6 +2340,24 @@ if test "$enable_autoservername" = "yes"; then
   AC_DEFINE(FEAT_AUTOSERVERNAME)
 fi
 
+AC_MSG_CHECKING(--enable-socketserver argument)
+AC_ARG_ENABLE(socketserver,
+	[  --enable-socketserver Use sockets for clientserver communication.],
+	[enable_socketserver=$enableval],
+	AS_IF([test "x$features" = xtiny], 
+			[enable_socketserver=no_auto
+			 AC_MSG_RESULT([cannot use socketserver with tiny features])],
+			[enable_socketserver=auto]))
+if test "$enable_socketserver" = "yes"; then
+  AC_DEFINE(WANT_SOCKETSERVER)
+  AC_MSG_RESULT([yes])
+elif test "$enable_socketserver" = "auto"; then
+  AC_DEFINE(MAYBE_SOCKETSERVER)
+  AC_MSG_RESULT([auto])
+elif test "$enable_socketserver" = "no"; then
+  AC_MSG_RESULT([no])
+fi
+
 AC_MSG_CHECKING(--enable-multibyte argument)
 AC_ARG_ENABLE(multibyte,
 	[  --enable-multibyte      Include multibyte editing support.], ,

src/errors.h

@@ -3782,3 +3782,15 @@ EXTERN char e_duplicate_type_var_name_str[]
 EXTERN char e_diff_anchors_with_hidden_windows[]
 	INIT(= N_("E1562: Diff anchors cannot be used with hidden diff windows"));
 #endif
+#ifdef FEAT_SOCKETSERVER
+EXTERN char e_socket_path_too_big[]
+	INIT(= N_("E1563: Socket path is too big"));
+EXTERN char e_socket_name_no_slashes[]
+	INIT(= N_("E1564: Socket name cannot have slashes in it without being a path"));
+EXTERN char e_socket_server_not_online[]
+	INIT(= N_("E1565: Socket server is not online, call remote_startserver() first"));
+EXTERN char e_socket_server_failed_connecting[]
+	INIT(= N_("E1566: Failed connecting to socket %s: %s"));
+EXTERN char e_socket_server_unavailable[]
+	INIT(= N_("E1567: Cannot start socket server, socket path is unavailable"));
+#endif

src/evalfunc.c

@@ -6765,6 +6765,13 @@ f_has(typval_T *argvars, typval_T *rettv)
 		1
 #else
 		0
+#endif
+		},
+	{"socketserver",
+#ifdef FEAT_SOCKETSERVER
+		1
+#else
+		0
 #endif
 		},
 	{"balloon_eval",

src/ex_docmd.c

@@ -10039,9 +10039,29 @@ eval_vars(
 
 #ifdef FEAT_CLIENTSERVER
 	case SPEC_CLIENT:	// Source of last submitted input
+#ifdef MSWIN
 		sprintf((char *)strbuf, PRINTF_HEX_LONG_U,
 							(long_u)clientWindow);
 		result = strbuf;
+#else
+# ifdef FEAT_SOCKETSERVER
+		if (clientserver_method == CLIENTSERVER_METHOD_SOCKET)
+		{
+		    if (client_socket == NULL)
+			result = (char_u *)"";
+		    else
+			result = client_socket;
+		}
+# endif
+# ifdef FEAT_X11
+		if (clientserver_method == CLIENTSERVER_METHOD_X11)
+		{
+		    sprintf((char *)strbuf, PRINTF_HEX_LONG_U,
+							(long_u)clientWindow);
+		    result = strbuf;
+		}
+# endif
+#endif
 		break;
 #endif
 

src/feature.h

@@ -945,11 +945,20 @@
 # define FIND_REPLACE_DIALOG 1
 #endif
 
+/*
+ * +socketserver	 Use UNIX domain sockets for clientserver communication
+ */
+#if defined(UNIX) && (defined(WANT_SOCKETSERVER) || \
+	(defined(MAYBE_SOCKETSERVER) && !defined(HAVE_X11)))
+#define FEAT_SOCKETSERVER
+#endif
+
 /*
  * +clientserver	Remote control via the remote_send() function
  *			and the --remote argument
  */
-#if (defined(MSWIN) || defined(FEAT_XCLIPBOARD)) && defined(FEAT_EVAL)
+#if (defined(MSWIN) || defined(FEAT_XCLIPBOARD) || defined(FEAT_SOCKETSERVER)) \
+    && defined(FEAT_EVAL)
 # define FEAT_CLIENTSERVER
 #endif
 

src/globals.h

@@ -1868,7 +1868,7 @@ EXTERN Window	commWindow INIT(= None);
 EXTERN Window	clientWindow INIT(= None);
 EXTERN Atom	commProperty INIT(= None);
 EXTERN char_u	*serverDelayedStartName INIT(= NULL);
-# else
+# elif defined(MSWIN)
 #  ifdef PROTO
 typedef int HWND;
 #  endif
@@ -2090,3 +2090,35 @@ EXTERN char *wayland_display_name INIT(= NULL);
 EXTERN int wayland_display_fd;
 
 #endif
+
+#if defined(FEAT_CLIENTSERVER) && !defined(MSWIN)
+
+// Backend for clientserver functionality
+typedef enum {
+    CLIENTSERVER_METHOD_NONE,
+    CLIENTSERVER_METHOD_X11,
+    CLIENTSERVER_METHOD_SOCKET
+} clientserver_method_T;
+
+// Default to X11 if compiled with support for it, else use socket server.
+# if defined(FEAT_X11) && defined(FEAT_SOCKETSERVER)
+EXTERN clientserver_method_T clientserver_method
+# else
+// Since we aren't going to be changing clientserver_method, make it constant to
+// allow compiler optimizations.
+EXTERN const clientserver_method_T clientserver_method
+# endif
+# ifdef FEAT_X11
+INIT(= CLIENTSERVER_METHOD_X11);
+# elif defined(FEAT_SOCKETSERVER)
+INIT(= CLIENTSERVER_METHOD_SOCKET);
+# else
+INIT(= CLIENTSERVER_METHOD_NONE);
+# endif
+
+#endif
+
+#ifdef FEAT_SOCKETSERVER
+// Path to socket of last client that communicated with us
+EXTERN char_u *client_socket INIT(= NULL);
+#endif

src/gui.c

@@ -150,6 +150,12 @@ gui_start(char_u *arg UNUSED)
 	// Reset clipmethod to CLIPMETHOD_NONE
 	choose_clipmethod();
 
+#ifdef FEAT_SOCKETSERVER
+    // Install socket server listening socket if we are running it
+    if (socket_server_valid())
+	gui_gtk_init_socket_server();
+#endif
+
     vim_free(old_term);
 
     // If the GUI started successfully, trigger the GUIEnter event, otherwise

src/gui_gtk_x11.c

@@ -99,6 +99,13 @@ extern void bonobo_dock_item_set_behavior(BonoboDockItem *dock_item, BonoboDockI
 # include <X11/Sunkeysym.h>
 #endif
 
+#ifdef FEAT_SOCKETSERVER
+# include <glib-unix.h>
+
+// Used to track the source for the listening socket
+static uint socket_server_source_id = 0;
+#endif
+
 /*
  * Easy-to-use macro for multihead support.
  */
@@ -2688,6 +2695,53 @@ global_event_filter(GdkXEvent *xev,
 }
 #endif // !USE_GNOME_SESSION
 
+#ifdef FEAT_SOCKETSERVER
+
+/*
+ * Callback for new events from the socket server listening socket
+ */
+    static int
+socket_server_poll_in(int fd UNUSED, GIOCondition cond, void *user_data UNUSED)
+{
+    if (cond & G_IO_IN)
+	socket_server_accept_client();
+    else if (cond & (G_IO_ERR | G_IO_HUP))
+    {
+	socket_server_uninit();
+	return FALSE;
+    }
+
+    return TRUE;
+}
+
+/*
+ * Initialize socket server for use in the GUI (does not actually initialize the
+ * socket server, only attaches a source).
+ */
+    void
+gui_gtk_init_socket_server(void)
+{
+    if (socket_server_source_id > 0)
+	return;
+    // Register source for file descriptor to global default context
+    socket_server_source_id = g_unix_fd_add(socket_server_get_fd(),
+	    G_IO_IN | G_IO_ERR | G_IO_HUP, socket_server_poll_in, NULL);
+}
+
+/*
+ * Remove the source for the socket server listening socket.
+ */
+    void
+gui_gtk_uninit_socket_server(void)
+{
+    if (socket_server_source_id > 0)
+    {
+	g_source_remove(socket_server_source_id);
+	socket_server_source_id = 0;
+    }
+}
+
+#endif
 
 /*
  * Setup the window icon & xcmdsrv comm after the main window has been realized.
@@ -2754,7 +2808,7 @@ mainwin_realize(GtkWidget *widget UNUSED, gpointer data UNUSED)
 	setup_save_yourself();
 
 #ifdef FEAT_CLIENTSERVER
-    if (gui_mch_get_display())
+    if (clientserver_method == CLIENTSERVER_METHOD_X11 && gui_mch_get_display())
     {
 	if (serverName == NULL && serverDelayedStartName != NULL)
 	{

src/if_xcmdsrv.c

@@ -14,7 +14,7 @@
 #include "vim.h"
 #include "version.h"
 
-#if defined(FEAT_CLIENTSERVER) || defined(PROTO)
+#if (defined(FEAT_CLIENTSERVER) && defined(FEAT_X11)) || defined(PROTO)
 
 # ifdef FEAT_X11
 #  include <X11/Intrinsic.h>

src/main.c

@@ -1855,7 +1855,8 @@ getout(int exitval)
  * Get the name of the display, before gui_prepare() removes it from
  * argv[].  Used for the xterm-clipboard display.
  *
- * Also find the --server... arguments and --socketid and --windowid
+ * Also find the --server, --clientserver... arguments and --socketid and
+ * --windowid
  */
     static void
 early_arg_scan(mparm_T *parmp UNUSED)
@@ -1900,6 +1901,22 @@ early_arg_scan(mparm_T *parmp UNUSED)
 		gui.dofork = FALSE;
 #  endif
 	}
+#  if defined(FEAT_X11) && defined(FEAT_SOCKETSERVER)
+	else if (STRNICMP(argv[i], "--clientserver", 14) == 0)
+	{
+	    char_u *arg;
+	    if (i == argc - 1)
+		mainerr_arg_missing((char_u *)argv[i]);
+	    arg = (char_u *)argv[++i];
+
+	    if (STRICMP(arg, "socket") == 0)
+		clientserver_method = CLIENTSERVER_METHOD_SOCKET;
+	    else if (STRICMP(arg, "x11") == 0)
+		clientserver_method = CLIENTSERVER_METHOD_X11;
+	    else
+		mainerr(ME_UNKNOWN_OPTION, arg);
+	}
+#  endif
 # endif
 
 # if defined(FEAT_GUI_GTK) || defined(FEAT_GUI_MSWIN)
@@ -2220,7 +2237,11 @@ command_line_scan(mparm_T *parmp)
 		else if (STRNICMP(argv[0] + argv_idx, "serverlist", 10) == 0)
 		    ; // already processed -- no arg
 		else if (STRNICMP(argv[0] + argv_idx, "servername", 10) == 0
-		       || STRNICMP(argv[0] + argv_idx, "serversend", 10) == 0)
+		       || STRNICMP(argv[0] + argv_idx, "serversend", 10) == 0
+# if defined(FEAT_X11) && defined(FEAT_SOCKETSERVER)
+		       || STRNICMP(argv[0] + argv_idx, "clientserver", 12) == 0
+# endif
+		       )
 		{
 		    // already processed -- snatch the following arg
 		    if (argc > 1)
@@ -3712,6 +3733,9 @@ usage(void)
     main_msg(_("-Y\t\t\tDo not connect to Wayland compositor"));
 #endif
 #ifdef FEAT_CLIENTSERVER
+# if defined(FEAT_X11) && defined(FEAT_SOCKETSERVER)
+    main_msg(_("--clientserver <socket|x11> Backend for clientserver communication"));
+# endif
     main_msg(_("--remote <files>\tEdit <files> in a Vim server if possible"));
     main_msg(_("--remote-silent <files>  Same, don't complain if there is no server"));
     main_msg(_("--remote-wait <files>  As --remote but wait for files to have been edited"));

src/po/vim.pot

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: Vim\n"
 "Report-Msgid-Bugs-To: vim-dev@vim.org\n"
-"POT-Creation-Date: 2025-08-16 17:57+0200\n"
+"POT-Creation-Date: 2025-08-18 21:30+0200\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -254,6 +254,9 @@ msgstr ""
 msgid "%d of %d edited"
 msgstr ""
 
+msgid "Socket server not online:Send expression failed"
+msgstr ""
+
 msgid "No display: Send expression failed.\n"
 msgstr ""
 
@@ -1711,6 +1714,9 @@ msgstr ""
 msgid "-Y\t\t\tDo not connect to Wayland compositor"
 msgstr ""
 
+msgid "--clientserver <socket|x11> Backend for clientserver communication"
+msgstr ""
+
 msgid "--remote <files>\tEdit <files> in a Vim server if possible"
 msgstr ""
 
@@ -2507,6 +2513,10 @@ msgstr ""
 msgid "XSMP SmcOpenConnection failed: %s"
 msgstr ""
 
+#, c-format
+msgid "Failed creating socket directory: %s"
+msgstr ""
+
 msgid "At line"
 msgstr ""
 
@@ -8806,6 +8816,22 @@ msgstr ""
 msgid "E1562: Diff anchors cannot be used with hidden diff windows"
 msgstr ""
 
+msgid "E1563: Socket path is too big"
+msgstr ""
+
+msgid "E1564: Socket name cannot have slashes in it without being a path"
+msgstr ""
+
+msgid "E1565: Socket server is not online, call remote_startserver() first"
+msgstr ""
+
+#, c-format
+msgid "E1566: Failed connecting to socket %s: %s"
+msgstr ""
+
+msgid "E1567: Cannot start socket server, socket path is unavailable"
+msgstr ""
+
 #. type of cmdline window or 0
 #. result of cmdline window or 0
 #. buffer of cmdline window or NULL

src/proto/gui_gtk_x11.pro

@@ -8,6 +8,8 @@ void gui_mch_stop_blink(int may_call_gui_update_cursor);
 void gui_mch_start_blink(void);
 int gui_mch_early_init_check(int give_message);
 int gui_mch_init_check(void);
+void gui_gtk_init_socket_server(void);
+void gui_gtk_uninit_socket_server(void);
 void gui_mch_set_dark_theme(int dark);
 void gui_mch_show_tabline(int showit);
 int gui_mch_showing_tabline(void);

src/proto/option.pro

@@ -68,6 +68,7 @@ char *did_set_shellslash(optset_T *args);
 char *did_set_shiftwidth_tabstop(optset_T *args);
 char *did_set_showtabline(optset_T *args);
 char *did_set_smoothscroll(optset_T *args);
+char *did_set_socktimeoutlen(optset_T *args);
 char *did_set_spell(optset_T *args);
 char *did_set_swapfile(optset_T *args);
 char *did_set_termguicolors(optset_T *args);

src/proto/optionstr.pro

@@ -34,6 +34,8 @@ int expand_set_casemap(optexpand_T *args, int *numMatches, char_u ***matches);
 int expand_set_clipboard(optexpand_T *args, int *numMatches, char_u ***matches);
 char *did_set_clipmethod(optset_T *args);
 int expand_set_clipmethod(optexpand_T *args, int *numMatches, char_u ***matches);
+char *did_set_clientserver(optset_T *args UNUSED);
+int expand_set_clientserver(optexpand_T *args, int *numMatches, char_u ***matches);
 char *did_set_chars_option(optset_T *args);
 int expand_set_chars_option(optexpand_T *args, int *numMatches, char_u ***matches);
 char *did_set_cinoptions(optset_T *args);

src/proto/os_unix.pro

@@ -94,4 +94,15 @@ void stop_timeout(void);
 volatile sig_atomic_t *start_timeout(long msec);
 void delete_timer(void);
 int mch_create_anon_file(void);
+int socket_server_init(char_u *sock_path);
+void socket_server_uninit(void);
+char_u *socket_server_list_sockets(void);
+void socket_server_accept_client(void);
+int socket_server_valid(void);
+int socket_server_send(char_u *sock_path, char_u *cmd, char_u **result, char_u **receiver, int is_expr, int timeout, int silent);
+int socket_server_read_reply(char_u *sender, char_u **str, int timeout);
+int socket_server_peek_reply(char_u *sender, char_u **str);
+int socket_server_send_reply(char_u *client, char_u *str);
+int socket_server_get_fd(void);
+int socket_server_waiting_accept(void);
 /* vim: set ft=c : */

src/testdir/test_clientserver.vim

@@ -10,6 +10,12 @@ CheckFeature clientserver
 
 source util/shared.vim
 
+" Unlike X11, we need the socket server running if we want to send commands to
+" a server via sockets.
+if v:servername == ""
+  call remote_startserver('VIMSOCKETSERVERTEST')
+endif
+
 func Check_X11_Connection()
   if has('x11')
     CheckX11
@@ -184,10 +190,18 @@ func Test_client_server()
   call assert_fails('call remote_startserver("")', 'E1175:')
   call assert_fails('call remote_startserver([])', 'E1174:')
   call assert_fails("let x = remote_peek([])", 'E730:')
-  call assert_fails("let x = remote_read('vim10')",
+
-        \ has('unix') ? ['E573:.*vim10'] : 'E277:')
+  " When using socket server, server id is not a number, but the path to the
-  call assert_fails("call server2client('abc', 'xyz')",
+  " socket.
-        \ has('unix') ? ['E573:.*abc'] : 'E258:')
+  if has('socketserver') && !has('X11')
+    call assert_fails("let x = remote_read('vim/10')", ['E573:.*vim/10'])
+    call assert_fails("call server2client('a/b/c', 'xyz')", ['E573:.*a/b/c'])
+  else
+    call assert_fails("let x = remote_read('vim10')",
+          \ has('unix') ? ['E573:.*vim10'] : 'E277:')
+    call assert_fails("call server2client('abc', 'xyz')",
+          \ has('unix') ? ['E573:.*abc'] : 'E258:')
+  endif
 endfunc
 
 func Test_client_server_stopinsert()
@@ -231,6 +245,121 @@ func Test_client_server_stopinsert()
   endtry
 endfunc
 
+" Test if socket server and X11 backends can be chosen and work properly.
+func Test_client_server_x11_and_socket_server()
+  CheckNotMSWindows
+  CheckFeature socketserver
+  CheckFeature x11
+
+  let g:test_is_flaky = 1
+  let cmd = GetVimCommand()
+
+  if cmd == ''
+    throw 'GetVimCommand() failed'
+  endif
+  call Check_X11_Connection()
+
+  let types = ['socket', 'x11']
+
+  for type in types
+    let name = 'VIMTEST_' .. toupper(type)
+    let actual_cmd = cmd .. ' --clientserver ' .. type
+    let actual_cmd .= ' --servername ' .. name
+    let job = job_start(actual_cmd, {'stoponexit': 'kill', 'out_io': 'null'})
+
+    call WaitForAssert({-> assert_equal("run", job_status(job))})
+    call WaitForAssert({-> assert_match(name, system(cmd .. ' --clientserver ' .. type .. ' --serverlist'))})
+
+    call assert_match(name, system(actual_cmd .. ' --remote-expr "v:servername"'))
+
+    call system(actual_cmd .. " --remote-expr 'execute(\"qa!\")'")
+    try
+      call WaitForAssert({-> assert_equal("dead", job_status(job))})
+    finally
+      if job_status(job) != 'dead'
+        call assert_report('Server did not exit')
+        call job_stop(job, 'kill')
+      endif
+    endtry
+  endfor
+endfunc
+
+" Test if socket server works in the GUI
+func Test_client_socket_server_server_gui()
+  CheckNotMSWindows
+  CheckFeature socketserver
+  CheckFeature gui_gtk
+
+  let g:test_is_flaky = 1
+  let cmd = GetVimCommand()
+
+  if cmd == ''
+    throw 'GetVimCommand() failed'
+  endif
+  call Check_X11_Connection()
+
+  let name = 'VIMTESTSOCKET'
+  let cmd .= ' --clientserver socket'
+  let cmd .= ' --servername ' .. name
+
+  let job = job_start(cmd, {'stoponexit': 'kill', 'out_io': 'null'})
+
+  call WaitForAssert({-> assert_equal("run", job_status(job))})
+  call WaitForAssert({-> assert_match(name, system(cmd .. ' --serverlist'))})
+
+  call system(cmd .. " --remote-expr 'execute(\"gui\")'")
+
+  call assert_match('1', system(cmd .. " --remote-expr 'has(\"gui_running\")'"))
+  call assert_match(name, system(cmd .. ' --remote-expr "v:servername"'))
+
+  call system(cmd .. " --remote-expr 'execute(\"qa!\")'")
+  try
+    call WaitForAssert({-> assert_equal("dead", job_status(job))})
+  finally
+    if job_status(job) != 'dead'
+      call assert_report('Server did not exit')
+      call job_stop(job, 'kill')
+    endif
+  endtry
+endfunc
+
+" Test if custom paths work for socketserver
+func Test_client_socket_server_custom_path()
+  CheckNotMSWindows
+  CheckFeature socketserver
+  CheckNotFeature x11
+
+  let g:test_is_flaky = 1
+  let cmd = GetVimCommand()
+
+  if cmd == ''
+    throw 'GetVimCommand() failed'
+  endif
+
+  let name = 'VIMTESTSOCKET2'
+
+  let paths = ['./' .. name, '../testdir/' .. name, getcwd(-1) .. '/' .. name]
+
+  for path in paths
+    let actual = cmd .. ' --servername ' .. path
+
+    let job = job_start(actual, {'stoponexit': 'kill', 'out_io': 'null'})
+
+    call WaitForAssert({-> assert_equal("run", job_status(job))})
+    call WaitForAssert({-> assert_equal(path, glob(path))})
+
+    call system(actual .. " --remote-expr 'execute(\"qa!\")'")
+    try
+      call WaitForAssert({-> assert_equal("dead", job_status(job))})
+    finally
+      if job_status(job) != 'dead'
+        call assert_report('Server did not exit')
+        call job_stop(job, 'kill')
+      endif
+    endtry
+  endfor
+endfunc
+
 " Uncomment this line to get a debugging log
 " call ch_logfile('channellog', 'w')
 

src/testdir/test_vim9_builtin.vim

@@ -3,6 +3,11 @@
 source util/screendump.vim
 import './util/vim9.vim' as v9
 
+" Socket backend for remote functions require the socket server to be running
+if v:servername == ""
+  call remote_startserver('VIMSOCKETSERVERTEST')
+endif
+
 " Test for passing too many or too few arguments to builtin functions
 func Test_internalfunc_arg_error()
   let l =<< trim END

src/testdir/test_wayland.vim

@@ -79,6 +79,10 @@ func Test_wayland_startup()
   call s:PreTest()
   call s:CheckXConnection()
 
+  if v:servername == ""
+    call remote_startserver('VIMSOCKETSERVER')
+  endif
+
   let l:name = 'WLVIMTEST'
   let l:cmd = GetVimCommand() .. ' --servername ' .. l:name
   let l:job = job_start(cmd, {'stoponexit': 'kill', 'out_io': 'null'})
@@ -372,6 +376,10 @@ func Test_wayland_autoselect_works()
 
   call writefile(l:lines, 'Wltester', 'D')
 
+  if v:servername == ""
+    call remote_startserver('VIMSOCKETSERVER')
+  endif
+
   let l:name = 'WLVIMTEST'
   let l:cmd = GetVimCommand() .. ' -S Wltester --servername ' .. l:name
   let l:job = job_start(cmd, {'stoponexit': 'kill', 'out_io': 'null'})
@@ -415,6 +423,10 @@ func Test_no_wayland_connect_cmd_flag()
   call s:PreTest()
   call s:CheckXConnection()
 
+  if v:servername == ""
+    call remote_startserver('VIMSOCKETSERVER')
+  endif
+
   let l:name = 'WLFLAGVIMTEST'
   let l:cmd = GetVimCommand() .. ' -Y --servername ' .. l:name
   let l:job = job_start(cmd, {'stoponexit': 'kill', 'out_io': 'null'})
@@ -453,6 +465,10 @@ func Test_wayland_become_inactive()
   call s:PreTest()
   call s:CheckXConnection()
 
+  if v:servername == ""
+    call remote_startserver('VIMSOCKETSERVER')
+  endif
+
   let l:name = 'WLLOSEVIMTEST'
   let l:cmd = GetVimCommand() .. ' --servername ' .. l:name
   let l:job = job_start(cmd, {
@@ -544,6 +560,10 @@ func Test_wayland_bad_environment()
   let l:old = $XDG_RUNTIME_DIR
   unlet $XDG_RUNTIME_DIR
 
+  if v:servername == ""
+    call remote_startserver('VIMSOCKETSERVER')
+  endif
+
   let l:name = 'WLVIMTEST'
   let l:cmd = GetVimCommand() .. ' --servername ' .. l:name
   let l:job = job_start(cmd, {

src/ui.c

@@ -407,7 +407,19 @@ inchar_loop(
 
 	if ((resize_func != NULL && resize_func(TRUE))
 #if defined(FEAT_CLIENTSERVER) && defined(UNIX)
-		|| server_waiting()
+		|| (
+# ifdef FEAT_X11
+		    (clientserver_method == CLIENTSERVER_METHOD_X11 &&
+		    server_waiting())
+# endif
+# if defined(FEAT_X11) && defined(FEAT_SOCKETSERVER)
+		    ||
+# endif
+# ifdef FEAT_SOCKETSERVER
+		    (clientserver_method == CLIENTSERVER_METHOD_SOCKET &&
+		     socket_server_waiting_accept())
+# endif
+		)
 #endif
 #ifdef MESSAGE_QUEUE
 		|| interrupted

src/version.c

@@ -516,6 +516,11 @@ static char *(features[]) =
 	"-signs",
 #endif
 	"+smartindent",
+#ifdef FEAT_SOCKETSERVER
+	"+socketserver",
+#else
+	"-socketserver",
+#endif
 #ifdef FEAT_SODIUM
 # ifdef DYNAMIC_SODIUM
 	"+sodium/dyn",
@@ -719,6 +724,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1651,
 /**/
     1650,
 /**/