Make event-handlers edge-triggered and move socket-state to Dart.

tests/standalone/io/socket_exception_test.dart

 // Copyright (c) 2013, 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:async";
 import "dart:io";
 
 import "package:async_helper/async_helper.dart";
@@ skipping 22 matching lines @@
       ServerSocket.bind("__INVALID_HOST__", 0)
         .then((server) { })
         .catchError((e) => e is SocketException);
     });
   }
 
   static void serverSocketCloseListenTest() {
     asyncStart();
     ServerSocket.bind("127.0.0.1", 0).then((server) {
       Socket.connect("127.0.0.1", server.port).then((socket) {
+        socket.destroy();
         server.close();
         server.listen(
           (incoming) => Expect.fail("Unexpected socket"),
           onDone: asyncEnd);
       });
     });
   }
 
   static void serverSocketListenCloseTest() {
     asyncStart();
     ServerSocket.bind("127.0.0.1", 0).then((server) {
       Socket.connect("127.0.0.1", server.port).then((socket) {
         server.listen(
-          (incoming) => server.close(),
-          onDone: asyncEnd);
+          (incoming) {
+            incoming.destroy();
+            socket.destroy();
+            server.close();
+          }, onDone: asyncEnd);
       });
     });
   }
 
   static void clientSocketExceptionTest() {
     bool exceptionCaught = false;
     bool wrongExceptionCaught = false;
 
     ServerSocket.bind("127.0.0.1", 0).then((server) {
       Expect.isNotNull(server);
@@ skipping 165 matching lines @@
     unknownHostTest();
   }
 }
 
 main() {
   asyncStart();
   SocketExceptionTest.testMain();
   asyncEnd();
 }