net: bind to :: TCP address by default

Try binding TCP socket to `::` first before falling back to
`0.0.0.0`.

Author: indutny

lib/net.js

@@ -1083,8 +1083,16 @@ var createServerHandle = exports._createServerHandle =
   }
 
   if (address || port) {
-    debug('bind to ' + address);
-    if (addressType === 6) {
+    debug('bind to ' + (address || 'anycast'));
+    if (!address) {
+      // Try binding to ipv6 first
+      err = handle.bind6('::', port);
+      if (err) {
+        handle.close();
+        // Fallback to ipv4
+        return createServerHandle('0.0.0.0', port);
+      }
+    } else if (addressType === 6) {
       err = handle.bind6(address, port);
     } else {
       err = handle.bind(address, port);
@@ -1214,7 +1222,7 @@ Server.prototype.listen = function() {
 
   if (arguments.length == 0 || util.isFunction(arguments[0])) {
     // Bind to a random port.
-    listen(self, '0.0.0.0', 0, null, backlog);
+    listen(self, null, 0, null, backlog);
 
   } else if (arguments[0] && util.isObject(arguments[0])) {
     var h = arguments[0];
@@ -1240,15 +1248,15 @@ Server.prototype.listen = function() {
              util.isFunction(arguments[1]) ||
              util.isNumber(arguments[1])) {
     // The first argument is the port, no IP given.
-    listen(self, '0.0.0.0', port, 4, backlog);
+    listen(self, null, port, 4, backlog);
 
   } else {
     // The first argument is the port, the second an IP.
     require('dns').lookup(arguments[1], function(err, ip, addressType) {
       if (err) {
         self.emit('error', err);
       } else {
-        listen(self, ip || '0.0.0.0', port, ip ? addressType : 4, backlog);
+        listen(self, ip, port, ip ? addressType : 4, backlog);
       }
     });
   }