Test for server.listen() more carefully, fix bug

lib/net.js

@@ -1075,8 +1075,15 @@ Server.prototype.listen = function () {
     self.addListener('listening', lastArg);
   }
 
-  var port = toPort(arguments[0] != lastArg ? arguments[0] : null);
-  if (port === false) {
+  var port = toPort(arguments[0]);
+
+  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()
+    self.type = 'tcp4';
+    self.fd = socket(self.type);
+    self._doListen(port);
+  } else if (port === false) {
     // the first argument specifies a path
     self.fd = socket('unix');
     self.type = 'unix';
@@ -1101,12 +1108,6 @@ Server.prototype.listen = function () {
         }
       }
     });
-  } else if (!arguments[1]) {
-    // Don't bind(). OS will assign a port with INADDR_ANY.
-    // The port can be found with server.address()
-    self.type = 'tcp4';
-    self.fd = socket(self.type);
-    self._doListen(port);
   } else {
     // the first argument is the port, the second an IP
     require('dns').lookup(arguments[1], function (err, ip, addressType) {

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

@@ -0,0 +1,49 @@
+var common = require('../common');
+var assert = require('assert');
+var net = require('net');
+
+
+// With only a callback, server should get a port assigned by the OS
+
+var address0;
+var server0 = net.createServer(function (socket) { });
+
+server0.listen(function() {
+  address0 = server0.address();
+  console.log("address0 %j", address0);
+  server0.close();
+});
+
+
+// No callback to listen(), assume we can bind in 100 ms
+
+var address1;
+var server1 = net.createServer(function(socket) { });
+
+server1.listen(common.PORT);
+
+setTimeout(function () {
+  address1 = server1.address()
+  console.log("address1 %j", address1);
+  server1.close();
+}, 100);
+
+
+// Callback to listen()
+
+var address2;
+var server2 = net.createServer(function(socket) { });
+
+server2.listen(common.PORT+1, function () {
+  address2 = server2.address()
+  console.log("address2 %j", address2);
+  server2.close();
+});
+
+
+
+process.on('exit', function () {
+  assert.ok(address0.port > 100);
+  assert.equal(common.PORT, address1.port);
+  assert.equal(common.PORT+1, address2.port);
+});

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

@@ -1,19 +0,0 @@
-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);
-});
-