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

tests/standalone/io/socket_info_test.dart

Index: tests/standalone/io/socket_info_test.dart
diff --git a/tests/standalone/io/socket_info_test.dart b/tests/standalone/io/socket_info_test.dart
index 7a5a20f4861e9cb32616dc0f886cba0c4c1c86da..eb14246bc618a35db6cad794d2fe5c205bc553be 100644
--- a/tests/standalone/io/socket_info_test.dart
+++ b/tests/standalone/io/socket_info_test.dart
@@ -15,7 +15,8 @@ void testHostAndPort() {
         Expect.equals(clientSocket.remotePort, socket.port);
         Expect.equals(socket.remoteAddress.address, "127.0.0.1");
         Expect.equals(clientSocket.remoteAddress.address, "127.0.0.1");
-
+        socket.destroy();
+        clientSocket.destroy();
         server.close();
       });
     });