--- a/mapsearch.c	Thu Jun 11 13:11:05 2020 +0300
+++ b/mapsearch.c	Tue Jun 30 13:43:01 2020 +0300
@@ -51,6 +51,8 @@
     char *vhostname;         // Vhost name
     int port;                // Port number
 
+    int ipvMode;             // Enable/disable IPv4/6 support for this listener
+
     BOOL useSSL;             // Use SSL/TLS?
     char *sslCertFile,       // Certificate file
          *sslKeyFile,        // Key file
@@ -129,16 +131,18 @@
     fprintf(stdout,
         "\n"
         "Listening interface(s) are specified with following syntax:\n"
-        "-l \"<interface/IP/host>:<port>[=<SSL/TLS spec>]\"\n"
+        "-l \"<interface/IP/host>:<port>[:no-ipv(4|6)][=<SSL/TLS spec>]\"\n"
         "\n"
         "IPv6 addresses should be specified with the square bracket notation [].\n"
         "To listen to all interfaces, you can specify an asterisk (*) as host:\n"
         "\n"
         "-l *:3491 -l *:3492=<vhostname for SNI>:<ssl_cert_file.crt>:<ssl_key_file.key>:<ca_file.crt>\n"
         "\n"
-        "Would listen for normal WebSocket (ws://) connections on port 3491 and for\n"
+        "This would listen for normal WebSocket (ws://) connections on port 3491 and for\n"
         "secure SSL/TLS WebSocket (wss://) connections on port 3492 of all interfaces.\n"
         "\n"
+        "To disable listening on IPv4/6 addresses, specify :no-ipv4 or :no-ipv6\n"
+        "\n"
         "Maps and location files for each map are specified as follows:\n"
         "<filename.map>:<locfilename.loc>:<map/continent name>[:<world x-offset>:<world y-offset>]\n"
         "World offsets are optional and default to 0, 0 if not specified.\n"
@@ -346,7 +350,19 @@
     *end++ = 0;
     start = end;
 
-    // Check for '=flags' at the end
+    // Check for ':no-ipv4' or ':no-ipv6' flag
+    if ((end = strstr(start, ":no-ipv")) != NULL &&
+        (end[7] == '4' || end[7] == '6'))
+    {
+        *end = 0;
+
+        if (end[7] == '4')
+            ctx->ipvMode = 6;
+        else
+            ctx->ipvMode = 4;
+    }
+
+    // Check for '=<SSL/TLS spec>' at the end
     if ((flags = strchr(start, '=')) != NULL)
         *flags++ = 0;
 
@@ -1866,14 +1882,37 @@
     // Create listener LWS vhosts ..
     for (int n = 0; n < optNListenTo; n++)
     {
+        char *ipvMode = "";
         ctx = optListenTo[n];
 
+        info.port = ctx->port;
+        info.iface = ctx->interface;
+        info.options = 0;
+
+        switch (ctx->ipvMode)
+        {
+            case 0:
+                ipvMode = " [IPv4 + IPv6]";
+                break;
+
+            case 4:
+                ipvMode = " [IPv4 only]";
+                info.options |= LWS_SERVER_OPTION_DISABLE_IPV6;
+                break;
+
+            case 6:
+                ipvMode = " [IPv6 only]";
+                info.options |= LWS_SERVER_OPTION_IPV6_V6ONLY_MODIFY | LWS_SERVER_OPTION_IPV6_V6ONLY_VALUE;
+                break;
+        }
+
         if (ctx->useSSL)
         {
-            mapMSG(1, "Listen to %s:%d (wss) [vhost='%s', cert='%s', key='%s', ca='%s']\n",
+            mapMSG(1, "Listen to %s:%d (wss) [vhost='%s', cert='%s', key='%s', ca='%s']%s\n",
                 ctx->interface != NULL ? ctx->interface : "*", ctx->port,
                 ctx->vhostname,
-                ctx->sslCertFile, ctx->sslKeyFile, ctx->sslCAFile);
+                ctx->sslCertFile, ctx->sslKeyFile, ctx->sslCAFile,
+                ipvMode);
 
             info.vhost_name = ctx->vhostname;
             info.ssl_cert_filepath = ctx->sslCertFile;
@@ -1882,8 +1921,10 @@
         }
         else
         {
-            mapMSG(1, "Listen to %s:%d (ws)\n",
-                ctx->interface != NULL ? ctx->interface : "*", ctx->port);
+            mapMSG(1, "Listen to %s:%d (ws)%s\n",
+                ctx->interface != NULL ? ctx->interface : "*",
+                ctx->port,
+                ipvMode);
 
             info.vhost_name = NULL;
             info.ssl_cert_filepath = NULL;
@@ -1891,9 +1932,6 @@
             info.ssl_ca_filepath = NULL;
         }
 
-        info.port = ctx->port;
-        info.iface = ctx->interface;
-
         if ((ctx->vhost = lws_create_vhost(setLWSContext, &info)) == NULL)
         {
             mapERR("LWS vhost creation failed!\n");