On Windows, the return value of socket() should be compared with

net/socket/tcp_server_socket_win.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/socket/tcp_server_socket_win.h"
 
 #include <mstcpip.h>
 
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
@@ skipping 27 matching lines @@
   DCHECK_EQ(socket_, INVALID_SOCKET);
   DCHECK_EQ(socket_event_, WSA_INVALID_EVENT);
 
   socket_event_ = WSACreateEvent();
   if (socket_event_ == WSA_INVALID_EVENT) {
     PLOG(ERROR) << "WSACreateEvent()";
     return ERR_FAILED;
   }
 
   socket_ = socket(address.GetSockAddrFamily(), SOCK_STREAM, IPPROTO_TCP);
-  if (socket_ < 0) {
+  if (socket_ == INVALID_SOCKET) {

[wtc, 2013/08/12 17:31:30]

See the "Return value" section and example code in
http://msdn.microsoft.com/en-us/library/windows/desktop/ms740506%28v=vs.85%29...

     PLOG(ERROR) << "socket() returned an error";
     return MapSystemError(WSAGetLastError());
   }
 
   if (SetNonBlocking(socket_)) {
     int result = MapSystemError(WSAGetLastError());
     Close();
     return result;
   }
 
@@ skipping 149 matching lines @@
     if (result != ERR_IO_PENDING) {
       accept_socket_ = NULL;
       CompletionCallback callback = accept_callback_;
       accept_callback_.Reset();
       callback.Run(result);
     }
   }
 }
 
 }  // namespace net