Add support to specify the source address for socket connect

sdk/lib/io/socket.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 
 /**
  * [InternetAddressType] is the type an [InternetAddress]. Currently,
  * IP version 4 (IPv4) and IP version 6 (IPv6) are supported.
@@ skipping 435 matching lines @@
   /**
    * Creates a new socket connection to the host and port and returns a [Future]
    * that will complete with either a [RawSocket] once connected or an error
    * if the host-lookup or connection failed.
    *
    * [host] can either be a [String] or an [InternetAddress]. If [host] is a
    * [String], [connect] will perform a [InternetAddress.lookup] and try
    * all returned [InternetAddress]es, until connected. Unless a
    * connection was established, the error from the first failing connection is
    * returned.
+   *
+   * The argument [sourceAddress] can be used to specify the local
+   * address to bind when making the connection. `sourceAddress` can either
+   * be a `String` or an `InternetAddress`. If a `String` is passed it must
+   * hold a numeric IP address.
    */
-  external static Future<RawSocket> connect(host, int port);
+  external static Future<RawSocket> connect(host, int port, {sourceAddress});
 
   /**
    * Returns the number of received and non-read bytes in the socket that
    * can be read.
    */
   int available();
 
   /**
    * Read up to [len] bytes from the socket. This function is
    * non-blocking and will only return data if data is available. The
@@ skipping 71 matching lines @@
   /**
    * Creates a new socket connection to the host and port and returns a [Future]
    * that will complete with either a [Socket] once connected or an error
    * if the host-lookup or connection failed.
    *
    * [host] can either be a [String] or an [InternetAddress]. If [host] is a
    * [String], [connect] will perform a [InternetAddress.lookup] and try
    * all returned [InternetAddress]es, until connected. Unless a
    * connection was established, the error from the first failing connection is
    * returned.
+   *
+   * The argument [sourceAddress] can be used to specify the local
+   * address to bind when making the connection. `sourceAddress` can either
+   * be a `String` or an `InternetAddress`. If a `String` is passed it must
+   * hold a numeric IP address.
    */
-  external static Future<Socket> connect(host, int port);
+  external static Future<Socket> connect(host, int port, {sourceAddress});
 
   /**
    * Destroy the socket in both directions. Calling [destroy] will make the
    * send a close event on the stream and will no longer react on data being
    * piped to it.
    *
    * Call [close](inherited from [IOSink]) to only close the [Socket]
    * for sending data.
    */
   void destroy();
@@ skipping 179 matching lines @@
     }
     if (address != null) {
       sb.write(", address = ${address.host}");
     }
     if (port != null) {
       sb.write(", port = $port");
     }
     return sb.toString();
   }
 }