From: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Date: Sun, 15 Mar 2026 09:22:29 +0000 (+0000)
Subject: patch 9.2.0170: channel: some issues in ch_listen()
X-Git-Tag: v9.2.0170^0
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e05d897258a6c3d0463fb6d76aaeb4f0534cd13f;p=thirdparty%2Fvim.git

patch 9.2.0170: channel: some issues in ch_listen()

Problem:  channel: some issues in ch_listen()
          (char101, after v9.2.0153)
Solution: On MS-Windows, initialize using channel_init_winsock() and use
          SO_EXCLUSIVEADDRUSE instead of SO_REUSEADDR, allow to use port
          0 to have the OS assign a port (Yasuhiro Matsumoto).

related: #19231
closes:  #19690

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Yasuhiro Matsumoto <mattn.jp@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
---

diff --git a/src/channel.c b/src/channel.c
index f35cbf8ead..6f06517fd7 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -1440,7 +1440,7 @@ channel_listen_func(typval_T *argvars)
 	    return NULL;
 	}
 	port = strtol((char *)(p + 1), &rest, 10);
-	if (port <= 0 || port >= 65536 || *rest != NUL)
+	if (port < 0 || port >= 65536 || *rest != NUL)
 	{
 	    semsg(_(e_invalid_argument_str), address);
 	    return NULL;
@@ -1459,7 +1459,7 @@ channel_listen_func(typval_T *argvars)
 	    return NULL;
 	}
 	port = strtol((char *)(p + 1), &rest, 10);
-	if (port <= 0 || port >= 65536 || *rest != NUL)
+	if (port < 0 || port >= 65536 || *rest != NUL)
 	{
 	    semsg(_(e_invalid_argument_str), address);
 	    return NULL;
@@ -1511,6 +1511,10 @@ channel_listen(
     int			val = 1;
     channel_T		*channel;
 
+#ifdef MSWIN
+    channel_init_winsock();
+#endif
+
     channel = add_channel();
     if (channel == NULL)
     {
@@ -1555,7 +1559,7 @@ channel_listen(
     }
 
 #ifdef MSWIN
-    if (setsockopt(sd, SOL_SOCKET, SO_REUSEADDR,
+    if (setsockopt(sd, SOL_SOCKET, SO_EXCLUSIVEADDRUSE,
 				    (const char *)&val, sizeof(val)) < 0)
 #else
     if (setsockopt(sd, SOL_SOCKET, SO_REUSEADDR,
@@ -1591,6 +1595,16 @@ channel_listen(
 	return NULL;
     }
 
+    // When port 0 was specified, retrieve the actual port assigned by the OS.
+    if (port_in == 0)
+    {
+	struct sockaddr_in	addr;
+	socklen_t		addr_len = sizeof(addr);
+
+	if (getsockname(sd, (struct sockaddr *)&addr, &addr_len) == 0)
+	    port_in = ntohs(addr.sin_port);
+    }
+
     channel->ch_listen = TRUE;
     channel->CH_SOCK_FD = (sock_T)sd;
     channel->ch_nb_close_cb = nb_close_cb;
diff --git a/src/testdir/test_channel.vim b/src/testdir/test_channel.vim
index 431eaab261..94dec0d973 100644
--- a/src/testdir/test_channel.vim
+++ b/src/testdir/test_channel.vim
@@ -2798,8 +2798,11 @@ func Test_listen_invalid_address()
     " port number too large
     call assert_fails("call ch_listen('localhost:99999')", 'E475:')
 
-    " port number zero
-    call assert_fails("call ch_listen('localhost:0')", 'E475:')
+    " port number zero should let the OS assign an available port
+    let ch = ch_listen('localhost:0')
+    call assert_equal('open', ch_status(ch))
+    call assert_notequal(0, ch_info(ch).port)
+    call ch_close(ch)
 
     " port number negative
     call assert_fails("call ch_listen('localhost:-1')", 'E475:')
diff --git a/src/version.c b/src/version.c
index 4f9c944a62..38e48f4a11 100644
--- a/src/version.c
+++ b/src/version.c
@@ -734,6 +734,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    170,
 /**/
     169,
 /**/