Add a web socket client

runtime/bin/websocket.dart

Index: runtime/bin/websocket.dart
diff --git a/runtime/bin/websocket.dart b/runtime/bin/websocket.dart
index f7a36f8fcfde41fe3e50c8a29e0e99ba28968bc9..cca6747b4ce60edb947764cd99b43ba3015905d9 100644
--- a/runtime/bin/websocket.dart
+++ b/runtime/bin/websocket.dart
@@ -34,7 +34,7 @@ interface WebSocketHandler default _WebSocketHandler {
 
 
 /**
- * Web socket connection.
+ * Server web socket connection.
  */
 interface WebSocketConnection {
   /**
@@ -71,6 +71,76 @@ interface WebSocketConnection {
 }
 
 
+/**
+ * Client web socket connection.
+ */
+interface WebSocketClientConnection default _WebSocketClientConnection {
+  /**
+   * Creates a new web socket client connection based on a HTTP client
+   * connection. The HTTP client connection must be freshly opened.
+   */
+  WebSocketClientConnection(HttpClientConnection conn,
+                            [List<String> protocols]);
+
+  /**
+   * Sets the callback to be called when the request object for the
+   * opening handshake request is ready. This callback can be used if
+   * one need to add additional headers to the opening handshake
+   * request.
+   */
+  void set onRequest(void callback(HttpClientRequest request));
+
+  /**
+   * Sets the callback to be called when a web socket connection has
+   * been established.
+   */
+  void set onOpen(void callback());
+
+  /**
+   * Sets the callback to be called when a message have been
+   * received. The type of [message] is either [:String:] or
+   * [:List<int>:] depending on whether it is a text or binary
+   * message. If the message is empty [message] will be [:null:].
+   */
+  void set onMessage(void callback(message));
+
+  /**
+   * Sets the callback to be called when the web socket connection is
+   * closed.
+   */
+  void set onClosed(void callback(int status, String reason));
+
+  /**
+   * Sets the callback to be called when the response object for the
+   * opening handshake did not cause a web socket connection
+   * upgrade. This will be called in case the response status code is
+   * not 101 (Switching Protocols). If this callback is not set the
+   * [:onError:] callback will be called if the server did not upgrade
+   * the connection.
+   */
+  void set onNoUpgrade(void callback(HttpClientResponse response));
+
+  /**
+   * Sets the callback to be called when the web socket connection
+   * encountered an error.
+   */
+  void set onError(void callback(e));
+
+  /**
+   * Sends a message. The [message] must be a [:String:] or a
+   * [:List<int>:]. To send an empty message use either an empty
+   * [:String:] or an empty [:List<int>:]. [:null:] cannot be used.
+   */
+  send(message);
+
+  /**
+   * Close the web socket connection. The default value for [status]
+   * and [reason] are [:null:].
+   */
+  close([int status, String reason]);
+}
+
+
 class WebSocketException implements Exception {
   const WebSocketException([String this.message = ""]);
   String toString() => "WebSocketException: $message";