Start better error reporting for sockets

tests/standalone/src/io/SocketManyConnectionsTest.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.
 //
 // Test creating a large number of socket connections.
 
 #import("dart:io");
 #import("dart:isolate");
 #source("TestingServer.dart");
 
@@ skipping 56 matching lines @@
 
 class TestServer extends TestingServer {
 
   void onConnection(Socket connection) {
     Socket _client;
 
     void closeHandler() {
       connection.close();
     }
 
-    void errorHandler() {
-      print("Socket error");
+    void errorHandler(Exception e) {
+      print("Socket error $e");
       connection.close();
     }
 
     _connections++;
     connection.onClosed = closeHandler;
     connection.onError = errorHandler;
   }
 
   int _connections = 0;
 }
 
 main() {
   SocketManyConnectionsTest test = new SocketManyConnectionsTest.start();
 }