Manage include order of <WinSock2.h> and <Windows.h> [duplicate] - c++

Question

I'm having a problem including both files.
Now, I know I need to either include Winsock2 first, then windows.h, or simply put:
#define WIN32_LEAN_AND_MEAN
but, I'm still having problems
I have a header file that is called XS.h which looks like this
#ifndef XS_H
#define XS_H
#include <winsock2.h>
#include <ws2tcpip.h>
#include <Windows.h>
#endif
and I'm including XS.h in the header Client.h.
Client.h include is looks like this :
#ifndef CLIENT_H
#define CLIENT_H
#include "XS.h"
XS.h is my only include in Client.h, yet I still get errors (and as you can see, Winsockis included before windows.h
I'm getting about 78 errors, here are some of them :
Error 90 error C3861: 'WSASetLastError': identifier not found c:\program files (x86)\windows kits\8.0\include\um\ws2tcpip.h 703
Error 61 error C2375: 'WSAStartup' : redefinition; different linkage c:\program files (x86)\windows kits\8.0\include\um\winsock2.h 2296
Error 49 error C2375: 'send' : redefinition; different linkage c:\program files (x86)\windows kits\8.0\include\um\winsock2.h 2026
How can I solve this issue?
Thanks!
Edit: I've tried to use #define _WINSOCKAPI_ as well, though it did not resolve my problems...
I have winsock.h first, then windows.h, though it still does the error for me.

Answer 1

Make sure that <windows.h> doesn't include <winsock.h> (which provides many of the same declarations as <winsock2.h>). In the <winsock2.h> file on my system there is this line:
#define _WINSOCKAPI_ /* Prevent inclusion of winsock.h in windows.h */
The _WINSOCKAPI_ include guard may be an internal implementation detail, but as a practical solution I would rely on it, just defining this symbol before including <windows.h>, e.g. in the compiler invocation (which for an IDE means in the IDE project settings).
Alternatively you can try to always include <winsock2.h> before <windows.h>, in order to establish the relevant include guard whatever it is (but this is I think much more fragile than just assuming that the above guard is practically well-defined);
or you can define WIN32_LEAN_AND_MEAN, which prevents <windows.h> from including <winsock.h> but also some other headers (listing from source on my system those are <cderr.h>, <dde.h>, <ddeml.h>, <dlgs.h>, <lzexpand.h>, <mmsystem.h>, <nb30.h>, <rpc.h>, <shellapi.h>, <winperf.h>, <wincrypt.h>, <winefs.h>, <winscard.h>, <winspool.h>, <ole2.h>, and <commdlg.h>). I do not recommend relying on WIN32_LEAN_AND_MEAN optimization for correctness.
I.e., minimum:
#undef UNICODE
#define UNICODE
#undef _WINSOCKAPI_
#define _WINSOCKAPI_
#include <windows.h>
#include <winsock2.h>
auto main()
-> int
{}

Answer 2

I made sure that an #include "Winsock2.h" is before any #include "windows.h" and "#include "Winsock.h" and this solved the case.
Just a matter of patience, look at includes one by one and establish this order, first #include "Winsock2.h" then #include "windows.h"
I checked the recursive includes, I spotted the header files which include (recursively) some #include "windows.h" and "#include "Winsock.h"and write a#include "Winsock2.h". in this files, i added#include "Winsock2.h"` as the first include.

Answer 3

Add the includes to pch.h:
// TODO: add headers that you want to pre-compile here
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
// Need to link with Ws2_32.lib, Mswsock.lib, and Advapi32.lib
#pragma comment (lib, "Ws2_32.lib")
#pragma comment (lib, "Mswsock.lib")
#pragma comment (lib, "AdvApi32.lib")