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

tests/standalone/io/socket_exception_test.dart

Index: tests/standalone/io/socket_exception_test.dart
diff --git a/tests/standalone/io/socket_exception_test.dart b/tests/standalone/io/socket_exception_test.dart
index 6381558f72a01ddcb5df0e0a2e6c541d670bf636..58abb85cbec6aee0fd5c358261195b25902aaf66 100644
--- a/tests/standalone/io/socket_exception_test.dart
+++ b/tests/standalone/io/socket_exception_test.dart
@@ -40,6 +40,7 @@ class SocketExceptionTest {
     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"),
@@ -53,8 +54,11 @@ class SocketExceptionTest {
     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);
       });
     });
   }