C++ redefinition due to including header files multiple times

As, the title says. I'm encountering redefinition errors due to including header files multiple times. I know its because of that, but I don't know how to resolve. Yes, I previously posted the same problem in SO an hour ahead. But I wasn't able to explain properly (I think so) and didn't get answers expected. Here is the link: C++ Redefinition Header Files I'm not editing that question since it has been filled up :). Okay I have some classes and the structure of them is like this: main.cpp: ``` #include "Server.h" #include "Handler.h" #include "Processor.h" int main(int argc, char* argv[]) { } ``` Server.h: ``` // Server.h #pragma once #include <winsock2.h> ``` Handler.h: ``` // Handler.h #pragma once #include <string> #include <vector> #include "Server.h" ``` Processor.cpp: ``` // Processor.cpp #include "StdAfx.h" #include "Processor.h" #include "Handler.h" ``` Server.cpp: ``` // Server.cpp #include "Server.h" #include "Processor.h" ``` The problem is that `<winsock2.h>` is included multiple times, don't know where but it is. #pragma once serves the same purpose as ``` #ifndef SOME_FILE_H #define SOME_FILE_H // code here #endif // SOME_FILE_H ``` in my compiler (MSVC2008 in this case). So I'm pretty much sure I don't need the header include guards. But can you spot where I'm doing the mistake by which `<winsock2.>` is included twice and how may I resolve? Thanks