Test and fix for self-assigned port from net.Server

lib/net.js

@@ -1075,7 +1075,7 @@ Server.prototype.listen = function () {
     self.addListener('listening', lastArg);
   }
 
-  var port = toPort(arguments[0]);
+  var port = toPort(arguments[0] != lastArg ? arguments[0] : null);
   if (port === false) {
     // the first argument specifies a path
     self.fd = socket('unix');

test/simple/test-net-server-listen-assigned-port.js

@@ -0,0 +1,19 @@
+var common = require('../common');
+net = require('net');
+assert = require('assert');
+
+var address;
+
+var server = net.createServer(function (socket) {
+});
+
+server.listen(function() {
+  address = server.address();
+  console.log("opened server on %j", address);
+  server.close();
+});
+
+process.on('exit', function () {
+  assert.ok(address.port > 100);
+});
+