net: type check createServer options object

net.createServer('aPipe') and net.createServer(8080) are mistakes,
and now throw a TypeError instead of silently being treated as an
object.

PR-URL: https://github.com/nodejs/node/pull/2904
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

lib/net.js

@@ -1090,12 +1090,14 @@ function Server(options, connectionListener) {
     connectionListener = options;
     options = {};
     self.on('connection', connectionListener);
-  } else {
+  } else if (options == null || typeof options === 'object') {
     options = options || {};
 
     if (typeof connectionListener === 'function') {
       self.on('connection', connectionListener);
     }
+  } else {
+    throw new TypeError('options must be an object');
   }
 
   this._connections = 0;

test/parallel/test-net-server-options.js

@@ -0,0 +1,7 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const net = require('net');
+
+assert.throws(function() { net.createServer('path'); }, TypeError);
+assert.throws(function() { net.createServer(common.PORT); }, TypeError);