Fixed racey testShutdown test, where echoServer was throwing an exception after trying to write to …

tests/standalone/io/raw_synchronous_socket_test.dart

 // Copyright (c) 2017, 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.
 
 import "dart:async";
 import "dart:io";
 import "dart:isolate";
 import "dart:math";
 
 import "package:async_helper/async_helper.dart";
@@ skipping 370 matching lines @@
 
     // Close from both directions. Shouldn't be able to read/write to the
     // socket.
     socket.shutdown(SocketDirection.BOTH);
     Expect.throws(
         () => socket.writeFromSync(data), (e) => e is SocketException);
     Expect.throws(
         () => socket.readSync(data.length), (e) => e is SocketException);
     socket.closeSync();
 
-    // Close the socket for reading, do a write, and see if we can get any
-    // response from the server (we shouldn't be able to).
+    // Close the socket for reading then try and perform a read. This should
+    // cause a SocketException.
     socket = RawSynchronousSocket.connectSync(
         LOOPBACK_IP_V4_STRING, serverInternetPort);
     socket.shutdown(SocketDirection.RECEIVE);

[siva, 2017/04/27 18:28:56]

Instead of deleting the write which is a good test to see if we are still able
to write after doing a READ shutdown, why not send some data which the echo
server recognizes and does not echo it back.

-    socket.writeFromSync(data);
     // Throws exception when the socket is closed for RECEIVE.
     Expect.throws(
         () => socket.readSync(data.length), (e) => e is SocketException);
     socket.closeSync();
 
     // Close the socket for writing and try to do a write. This should cause an
     // OSError to be throw as the pipe is closed for writing.
     socket = RawSynchronousSocket.connectSync(
         LOOPBACK_IP_V4_STRING, serverInternetPort);
     socket.shutdown(SocketDirection.SEND);
@@ skipping 74 matching lines @@
   await testShutdown();
   testSimpleConnect();
   testServerListenAfterConnect();
   await testSimpleReadWrite();
   await testPartialRead();
   await testPartialWrite();
   testInvalidReadWriteOperations();
   testClosedError();
   asyncEnd();
 }