Start better error reporting for sockets

tests/standalone/src/io/EchoServerTest.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.
 //
 // Echo server test program for testing sockets.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
@@ skipping 57 matching lines @@
             sendData();
           } else {
             shutdown();
           }
         }
       }
 
       handleRead();
     }
 
-    void errorHandler() {
-      Expect.fail("Socket error");
+    void errorHandler(Exception e) {
+      Expect.fail("Socket error $e");
     }
 
     void connectHandler() {
 
       void writeMessage() {
         int bytesWritten = 0;
 
         void handleWrite() {
           bytesWritten += _socket.writeList(
               _buffer, bytesWritten, MSGSIZE - bytesWritten);
@@ skipping 86 matching lines @@
         }
       }
 
       handleRead();
     }
 
     void closeHandler() {
       connection.close();
     }
 
-    void errorHandler() {
-      Expect.fail("Socket error");
+    void errorHandler(Exception e) {
+      Expect.fail("Socket error $e");
     }
 
     connection.onData = messageHandler;
     connection.onClosed = closeHandler;
     connection.onError = errorHandler;
   }
 }
 
 main() {
   EchoServerTest.testMain();
 }