net, http: add backlog parameter to .listen()

doc/api/http.markdown

@@ -117,7 +117,7 @@ sent to the server on that socket.
 
 If a client connection emits an 'error' event - it will forwarded here.
 
-### server.listen(port, [hostname], [callback])
+### server.listen(port, [hostname], [backlog], [callback])
 
 Begin accepting connections on the specified port and hostname.  If the
 hostname is omitted, the server will accept connections directed to any
@@ -125,6 +125,11 @@ IPv4 address (`INADDR_ANY`).
 
 To listen to a unix socket, supply a filename instead of port and hostname.
 
+Backlog is the maximum length of the queue of pending connections.
+The actual length will be determined by your OS through sysctl settings such as
+`tcp_max_syn_backlog` and `somaxconn` on linux. The default value of this
+parameter is 511 (not 512).
+
 This function is asynchronous. The last parameter `callback` will be added as
 a listener for the ['listening'](net.html#event_listening_) event.
 See also [net.Server.listen()](net.html#server.listen).

doc/api/net.markdown

@@ -121,12 +121,17 @@ The `connectListener` parameter will be added as an listener for the
 This class is used to create a TCP or UNIX server.
 A server is a `net.Socket` that can listen for new incoming connections.
 
-### server.listen(port, [host], [listeningListener])
+### server.listen(port, [host], [backlog], [listeningListener])
 
 Begin accepting connections on the specified `port` and `host`.  If the
 `host` is omitted, the server will accept connections directed to any
 IPv4 address (`INADDR_ANY`). A port value of zero will assign a random port.
 
+Backlog is the maximum length of the queue of pending connections.
+The actual length will be determined by your OS through sysctl settings such as
+`tcp_max_syn_backlog` and `somaxconn` on linux. The default value of this
+parameter is 511 (not 512).
+
 This function is asynchronous.  When the server has been bound,
 ['listening'](#event_listening_) event will be emitted.
 the last parameter `listeningListener` will be added as an listener for the

lib/net.js

@@ -56,7 +56,7 @@ if (process.env.NODE_DEBUG && /net/.test(process.env.NODE_DEBUG)) {
 
 
 function isPipeName(s) {
-  return typeof s === 'string' && toPort(s) === false;
+  return typeof s === 'string' && toNumber(s) === false;
 }
 
 
@@ -161,7 +161,7 @@ exports.Stream = Socket; // Legacy naming.
 Socket.prototype.listen = function() {
   var self = this;
   self.on('connection', arguments[0]);
-  listen(self, null, null);
+  listen(self, null, null, null);
 };
 
 
@@ -747,7 +747,7 @@ util.inherits(Server, events.EventEmitter);
 exports.Server = Server;
 
 
-function toPort(x) { return (x = Number(x)) >= 0 ? x : false; }
+function toNumber(x) { return (x = Number(x)) >= 0 ? x : false; }
 
 
 var createServerHandle = exports._createServerHandle =
@@ -786,7 +786,7 @@ var createServerHandle = exports._createServerHandle =
 };
 
 
-Server.prototype._listen2 = function(address, port, addressType) {
+Server.prototype._listen2 = function(address, port, addressType, backlog) {
   var self = this;
   var r = 0;
 
@@ -805,7 +805,10 @@ Server.prototype._listen2 = function(address, port, addressType) {
   self._handle.onconnection = onconnection;
   self._handle.socket = self;
 
-  r = self._handle.listen(self._backlog || 128);
+  // Use a backlog of 512 entries. We pass 511 to the listen() call because
+  // the kernel does: backlogsize = roundup_pow_of_two(backlogsize + 1);
+  // which will thus give us a backlog of 512 entries.
+  r = self._handle.listen(backlog || 511);
 
   if (r) {
     self._handle.close();
@@ -822,15 +825,15 @@ Server.prototype._listen2 = function(address, port, addressType) {
 };
 
 
-function listen(self, address, port, addressType) {
+function listen(self, address, port, addressType, backlog) {
   if (process.env.NODE_UNIQUE_ID) {
     var cluster = require('cluster');
     cluster._getServer(self, address, port, addressType, function(handle) {
       self._handle = handle;
-      self._listen2(address, port, addressType);
+      self._listen2(address, port, addressType, backlog);
     });
   } else {
-    self._listen2(address, port, addressType);
+    self._listen2(address, port, addressType, backlog);
   }
 }
 
@@ -843,36 +846,41 @@ Server.prototype.listen = function() {
     self.once('listening', lastArg);
   }
 
-  var port = toPort(arguments[0]);
+  var port = toNumber(arguments[0]);
+
+  // The third optional argument is the backlog size.
+  // When the ip is omitted it can be the second argument.
+  var backlog = toNumber(arguments[1]) || toNumber(arguments[2]);
 
   var TCP = process.binding('tcp_wrap').TCP;
 
   if (arguments.length == 0 || typeof arguments[0] == 'function') {
     // Don't bind(). OS will assign a port with INADDR_ANY.
     // The port can be found with server.address()
-    listen(self, null, null);
+    listen(self, null, null, backlog);
 
   } else if (arguments[0] instanceof TCP) {
     self._handle = arguments[0];
-    listen(self, null, -1, -1);
+    listen(self, null, -1, -1, backlog);
 
   } else if (isPipeName(arguments[0])) {
     // UNIX socket or Windows pipe.
     var pipeName = self._pipeName = arguments[0];
-    listen(self, pipeName, -1, -1);
+    listen(self, pipeName, -1, -1, backlog);
 
   } else if (typeof arguments[1] == 'undefined' ||
-             typeof arguments[1] == 'function') {
+             typeof arguments[1] == 'function' ||
+             typeof arguments[1] == 'number') {
     // The first argument is the port, no IP given.
-    listen(self, '0.0.0.0', port, 4);
+    listen(self, '0.0.0.0', port, 4, backlog);
 
   } else {
-    // The first argument is the port, the second an IP
+    // 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);
+        listen(self, ip || '0.0.0.0', port, ip ? addressType : 4, backlog);
       }
     });
   }

test/simple/test-net-server-bind.js

@@ -62,9 +62,34 @@ server2.listen(common.PORT + 1, function() {
 });
 
 
+// Backlog argument
+
+var address3;
+var server3 = net.createServer(function(socket) { });
+
+server3.listen(common.PORT + 2, '0.0.0.0', 127, function() {
+  address3 = server3.address();
+  console.log('address3 %j', address3);
+  server3.close();
+});
+
+
+// Backlog argument without host argument
+
+var address4;
+var server4 = net.createServer(function(socket) { });
+
+server4.listen(common.PORT + 3, 127, function() {
+  address4 = server4.address();
+  console.log('address4 %j', address4);
+  server4.close();
+});
+
 
 process.on('exit', function() {
   assert.ok(address0.port > 100);
   assert.equal(common.PORT, address1.port);
   assert.equal(common.PORT + 1, address2.port);
+  assert.equal(common.PORT + 2, address3.port);
+  assert.equal(common.PORT + 3, address4.port);
 });