Use patching for dart:io.

lib/io/socket.dart

 // Copyright (c) 2012, 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.
 
 abstract class ServerSocket {
   /**
    * Constructs a new server socket, binds it to a given address and port,
    * and listens on it.
    */
-  factory ServerSocket(String bindAddress, int port, int backlog) {
-    return new _ServerSocket(bindAddress, port, backlog);
-  }
+  external factory ServerSocket(String bindAddress, int port, int backlog);
 
   /**
    * The connection handler gets called when there is a new incoming
    * connection on the socket.
    */
   void set onConnection(void callback(Socket connection));
 
   /**
    * The error handler gets called when a socket error occurs.
    */
@@ skipping 10 matching lines @@
   void close();
 }
 
 
 abstract class Socket {
   /**
    * Constructs a new socket and initiate connecting it to the given
    * host on the given port. The returned socket is not yet connected
    * but ready for registration of callbacks.
    */
-  factory Socket(String host, int port) => new _Socket(host, port);
+  external factory Socket(String host, int port);
 
   /**
    * Returns the number of received and non-read bytes in the socket that
    * can be read.
    */
   int available();
 
   /**
    * Reads up to [count] bytes of data from the socket and stores them into
    * buffer after buffer offset [offset]. The number of successfully read
@@ skipping 89 matching lines @@
         sb.add(" ($osError)");
       }
     } else if (osError != null) {
       sb.add(": $osError");
     }
     return sb.toString();
   }
   final String message;
   final OSError osError;
 }