Use write instead of writeln for client/server communication.

pkg/analysis_server/lib/src/channel/byte_stream_channel.dart

 // Copyright (c) 2014, 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.
 
 library channel.byte_stream;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 31 matching lines @@
   }
 
   @override
   Future close() {
     return output.close();
   }
 
   @override
   Future<Response> sendRequest(Request request) {
     String id = request.id;
-    output.writeln(JSON.encode(request.toJson()));
+    output.write(JSON.encode(request.toJson()) + '\n');
     return responseStream.firstWhere((Response response) => response.id == id);
   }
 }
 
 /**
  * Instances of the class [ByteStreamServerChannel] implement a
  * [ServerCommunicationChannel] that uses a stream and a sink (typically,
  * standard input and standard output) to communicate with clients.
  */
 class ByteStreamServerChannel implements ServerCommunicationChannel {
@@ skipping 40 matching lines @@
   @override
   void sendNotification(Notification notification) {
     // Don't send any further notifications after the communication channel is
     // closed.
     if (_closed.isCompleted) {
       return;
     }
     ServerCommunicationChannel.ToJson.start();
     String jsonEncoding = JSON.encode(notification.toJson());
     ServerCommunicationChannel.ToJson.stop();
-    output.writeln(jsonEncoding);
+    output.write(jsonEncoding + '\n');
   }
 
   @override
   void sendResponse(Response response) {
     // Don't send any further responses after the communication channel is
     // closed.
     if (_closed.isCompleted) {
       return;
     }
     ServerCommunicationChannel.ToJson.start();
     String jsonEncoding = JSON.encode(response.toJson());
     ServerCommunicationChannel.ToJson.stop();
-    output.writeln(jsonEncoding);
+    output.write(jsonEncoding + '\n');
   }
 
   /**
    * Read a request from the given [data] and use the given function to handle
    * the request.
    */
   void _readRequest(Object data, void onRequest(Request request)) {
     // Ignore any further requests after the communication channel is closed.
     if (_closed.isCompleted) {
       return;
     }
     // Parse the string as a JSON descriptor and process the resulting
     // structure as a request.
     ServerCommunicationChannel.FromJson.start();
     Request request = new Request.fromString(data);
     ServerCommunicationChannel.FromJson.stop();
     if (request == null) {
       sendResponse(new Response.invalidRequestFormat());
       return;
     }
     onRequest(request);
   }
 }