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

tests/standalone/io/socket_port_test.dart

Index: tests/standalone/io/socket_port_test.dart
diff --git a/tests/standalone/io/socket_port_test.dart b/tests/standalone/io/socket_port_test.dart
index d9c75d705454de9e42caa53b8c8f27c06c98fa75..e7a24ec1606d0cc433d64ccb11cc8a881eed994d 100644
--- a/tests/standalone/io/socket_port_test.dart
+++ b/tests/standalone/io/socket_port_test.dart
@@ -9,9 +9,11 @@ void testPort() {
   ServerSocket.bind("127.0.0.1", 0).then((server) {
     Socket.connect("127.0.0.1", server.port).then((clientSocket) {
       server.listen((Socket socket) {
-          Expect.equals(socket.port, server.port);
+        Expect.equals(socket.port, server.port);
         Expect.equals(clientSocket.port, socket.remotePort);
         Expect.equals(clientSocket.remotePort, socket.port);
+        clientSocket.destroy();
+        socket.destroy();
         server.close();
       });
     });