Windows Sockets startup

/**
 * main.c
 * startup Windows Sockets demo
 * @author  : MJN
 * @date    : 2011-10-09
 */

#include < stdio.h >
#include < winsock2.h >
#pragma comment(lib, "ws2_32")

int main(int argc, char* argv[])
{
    WSADATA wsaData;
    
    /*
     * socket version: 2.2
     * return 0 if startup success
     */
    int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != 0)
    {
        printf("WSAStartup failed with error: %d\n", iResult);
        return -1;
    }
    if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) 
    {
        /* Tell the user that we could not find a usable */
        /* WinSock DLL.                                  */
        WSACleanup( );
        return -1; 
    }
    printf("WSAStartup succeeded.\n");
    printf("version:%x\n", wsaData.wVersion);       /* output: 202 (means 0x0202) */
    printf("high version:%x\n", wsaData.wHighVersion);
    printf("description:%s\n", wsaData.szDescription);
    printf("status:%s\n", wsaData.szSystemStatus);

    WSACleanup();

    return 0;
}

程序输出:

WSADATA的定义如下:

typedef struct WSAData {
  WORD           wVersion;
  WORD           wHighVersion;
  char           szDescription[WSADESCRIPTION_LEN+1];
  char           szSystemStatus[WSASYS_STATUS_LEN+1];
  unsigned short iMaxSockets;
  unsigned short iMaxUdpDg;
  char FAR       *lpVendorInfo;
} WSADATA, *LPWSADATA;

WSADATA的成员

wVersion:

Ws2_32.dll期望调用者使用的Windows Sockets规范的版本号. 高字节为次版本号, 低字节为主版本号

wHighVersion:Ws2_32.dll支持的最高版本号.

szDescription:

关于Windows Sockets实现的描述

szSystemStatus:

Windows Sockets的状态.

iMaxSockets, iMaxUdpDg, lpVendorInfo:

Windows Sockets版本2及以后的版本, 这三个成员被忽略.

程序在调用Windows socket 函数之前, 需要先初始化Windows socket动态链接库. 函数WSAStartup的声明如下:

int WSAStartup(
  __in   WORD wVersionRequested,
  __out  LPWSADATA lpWSAData
);

参数wVersionRequested是调用者可用的Windows Sockets最高版本号

参考:

1. MSDN

2. NNU姜老师网络编程课件

3. 《TCP/IP协议与网络编程》任泰明 编著 西安电子科技大学出版社

环境:

1. 开发: Microsoft Visual C++

2. 系统: Windows XP Professional