Throw an error if the ServerSocket host argument is invalid.

tests/standalone/io/socket_exception_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 //
 // Tests socket exceptions.
 
 #import("dart:isolate");
 #import("dart:io");
 
 class SocketExceptionTest {
@@ skipping 10 matching lines @@
     server.close();
     try {
       server.close();
     } on SocketIOException catch(ex) {
       exceptionCaught = true;
     } on Exception catch (ex) {
       wrongExceptionCaught = true;
     }
     Expect.equals(false, exceptionCaught);
     Expect.equals(true, !wrongExceptionCaught);
+
+    // Test invalid host.
+    Expect.throws(() => new ServerSocket("__INVALID_HOST__", PORT, 10),
+                  (e) => e is SocketIOException);
   }
 
   static void clientSocketExceptionTest() {
     bool exceptionCaught = false;
     bool wrongExceptionCaught = false;
 
     ServerSocket server = new ServerSocket(HOST, PORT, 10);
     Expect.equals(true, server !== null);
     int port = server.port;
     Socket client = new Socket(HOST, port);
@@ skipping 150 matching lines @@
     Socket s =  new Socket("127.0.0.1", 65535);
     s.onError = (e) => port.close();
     s.onConnect = () => Expect.fail("Connection completed");
   }
 
   static void testMain() {
     serverSocketExceptionTest();
     clientSocketExceptionTest();
     indexOutOfRangeExceptionTest();
     unknownHostTest();
+
     // TODO(sgjesse): This test seems to fail on the buildbot.
     //unresponsiveHostTest();
   }
 }
 
 main() {
   SocketExceptionTest.testMain();
 }