socket学习（一）

环境vs2008
1.把WinSock2.h头文件包含进来；
2.把Ws2_32.lib链接库加进来；
3.相关代码：
 1 void DoSocket()
 2 {
 3     WSADATA wsaData;
 4     WSAStartup(MAKEWORD(2, 0), &wsaData);
 5     SOCKET sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
 6     SOCKADDR_IN sa;
 7     sa.sin_family = AF_INET;
 8 
 9     sa.sin_port = htons(IPPORT_SMTP);
10     // 123.125.50.133 网易邮箱ip
11     sa.sin_addr.S_un.S_addr = inet_addr("123.125.50.133");
12     if (connect(sock, (SOCKADDR *)&sa, sizeof(sa)) == SOCKET_ERROR)
13     {
14         ShowError();
15         return;
16     }
17 
18     char buffer[256];
19     ZeroMemory(buffer, sizeof(buffer) / sizeof(char));
20     recv(sock, buffer, 256, 0);
21     MessageBox(NULL, buffer, "", 0);
22 
23     TCHAR cQuit[] = "QUIT\n";
24     send(sock, cQuit, lstrlen(cQuit), 0);
25     ZeroMemory(buffer, sizeof(buffer) / sizeof(char));
26 
27     recv(sock, buffer, 256, 0);
28     MessageBox(NULL, buffer, "", 0);
29 
30     closesocket(sock);
31     WSACleanup();
32 }
33 
34 void ShowError()
35 {
36     TCHAR* lpMsgBuf;
37     FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|
38         FORMAT_MESSAGE_FROM_SYSTEM,
39         NULL, GetLastError(),
40         MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
41         (LPTSTR)&lpMsgBuf,
42         0,
43         NULL);
44     MessageBox(NULL, lpMsgBuf, "", MB_ICONERROR);
45 }