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The original include file for use with Windows Sockets 1.1 was the
Winsock.h
header file. To ease porting existing source code based on Berkeley UNIX sockets to Windows sockets, Windows Sockets development kits for Winsock 1.1 were encouraged to be supplied with several include files with the same names as standard UNIX include files (the
sys/socket.h
and arpa/inet.h header files, for example). However, these similarly-name Winsock header files merely contained a directive to include the
Winsock2.h
header file.
When Windows Sockets 2 was released, the primary include file for use with Windows Sockets was renamed to
Winsock2.h
. The older original
Winsock.h
header file for Winsock 1.1 was also retained for compatibility with older applications. The development of Winsock 1.1 compatible applications has been deprecated since Windows 2000 was released. All applications should now use use the include
Winsock2.h
directive in Winsock application source files.
The
Winsock2.h
header file contains most of the Winsock functions, structures, and definitions. The
Ws2tcpip.h
header file contains definitions introduced in the WinSock 2 Protocol-Specific Annex document for TCP/IP that includes newer functions and structures used to retrieve IP addresses. These include the
getaddrinfo
and
getnameinfo
family of functions that provide name resolution for both IPv4 or IPv6 addresses. The
Ws2tcpip.h
header file is only needed if these IP-agnostic naming functions are required by the application.
The
Mswsock.h
header file contains definitions for Microsoft-specific extensions to the Windows Sockets 2 (
TransmitFile
,
AcceptEx
, and
ConnectEx
, for example). The
Mswsock.h
header file is not normally needed unless these Microsoft-specific extensions are used by the application.
The
Winsock2.h
header file internally includes core elements from the
Windows.h
header file, so there is not usually an #include line for the
Windows.h
header file in Winsock applications. If an #include line is needed for the
Windows.h
header file, this should be preceded with the #define WIN32_LEAN_AND_MEAN macro. For historical reasons, the
Windows.h
header defaults to including the
Winsock.h
header file for Windows Sockets 1.1. The declarations in the
Winsock.h
header file will conflict with the declarations in the
Winsock2.h
header file required by Windows Sockets 2. The WIN32_LEAN_AND_MEAN macro prevents the
Winsock.h
from being included by the
Windows.h
header. An example illustrating this is shown below.
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#pragma comment(lib, "Ws2_32.lib")
int main() {
return 0;
Creating a Basic Winsock Application
Getting Started With Winsock
Porting Socket Applications to Winsock
Winsock Programming Considerations
