Use 'print' to send responses/notifications to the client.

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 229 matching lines @@
     ServerCommunicationChannel.FromJson.start();
     Request request = new Request.fromString(data);
     ServerCommunicationChannel.FromJson.stop();
     if (request == null) {
       sendResponse(new Response.invalidRequestFormat());
       return;
     }
     onRequest(request);
   }
 }
+
+/**
+ * Instances of the class [PrintServerChannel] implement a
+ * [ServerCommunicationChannel] that uses standard input and [print]
+ * to communicate with clients.
+ */
+class PrintServerChannel implements ServerCommunicationChannel {
+  /**
+   * The instrumentation service that is to be used by this analysis server.
+   */
+  final InstrumentationService instrumentationService;
+
+  /**
+   * Completer that will be signalled when the input stream is closed.
+   */
+  final Completer _closed = new Completer();
+
+  /**
+   * True if [close] has been called.
+   */
+  bool _closeRequested = false;
+
+  PrintServerChannel(this.instrumentationService);
+
+  /**
+   * Future that will be completed when the input stream is closed.
+   */
+  Future get closed {
+    return _closed.future;
+  }
+
+  @override
+  void close() {
+    if (!_closeRequested) {
+      _closeRequested = true;
+      assert(!_closed.isCompleted);
+      _closed.complete();
+    }
+  }
+
+  @override
+  void listen(void onRequest(Request request), {Function onError, void
+      onDone()}) {
+    stdin.transform(
+        (new Utf8Codec()).decoder).transform(
+            new LineSplitter()).listen(
+                (String data) => _readRequest(data, onRequest),
+                onError: onError,
+                onDone: () {
+      close();
+      onDone();
+    });
+  }
+
+  @override
+  void sendNotification(Notification notification) {
+    // Don't send any further notifications after the communication channel is
+    // closed.
+    if (_closeRequested) {
+      return;
+    }
+    ServerCommunicationChannel.ToJson.start();
+    String jsonEncoding = JSON.encode(notification.toJson());
+    ServerCommunicationChannel.ToJson.stop();
+    print(jsonEncoding);
+    instrumentationService.logNotification(jsonEncoding);
+  }
+
+  @override
+  void sendResponse(Response response) {
+    // Don't send any further responses after the communication channel is
+    // closed.
+    if (_closeRequested) {
+      return;
+    }
+    ServerCommunicationChannel.ToJson.start();
+    String jsonEncoding = JSON.encode(response.toJson());
+    ServerCommunicationChannel.ToJson.stop();
+    print(jsonEncoding);
+    instrumentationService.logResponse(jsonEncoding);
+  }
+
+  /**
+   * 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;
+    }
+    instrumentationService.logRequest(data);
+    // 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);
+  }
+}