為了更容易理解，我們舉一個小例子來說明服務器與客戶端之間的連接過程。

有一個飯店，飯店裏有服務員，服務員用於招待客人

特別要註意的是：要記住相關函數的各個參數都是什麽，什麽時候返回SOCKET_ERROR,什麽時候返回INVALID_SOCKET

服務器

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

 5 int main()
 6 {
 7     //初始化wsa
 8     WORD wVersionRequested;
 9     WSADATA wsaData;
 
10     int err;
11     wVersionRequested = MAKEWORD(2, 2);
12 
13     err = WSAStartup(wVersionRequested, &wsaData);
14     if (err != 0)
15     {
16                       
17         printf("WSAStartup failed with error: %d\n", err);
18         return 1;
19     }
20 
21     if (LOBYTE(wsaData.wVersion) != 2
 
 || HIBYTE(wsaData.wVersion) != 2) 
22     {
23        
24         printf("Could not find a usable version of Winsock.dll\n");
25         WSACleanup();
26         return 1;
27     }
28     else
29         printf("The Winsock 2.2 dll was found okay\n");
30 
31     SOCKET sever;
32     SOCKET waiter;//服務員用於招待客人
 
33     struct sockaddr_in severaddr;
34     struct sockaddr_in clientaddr;37     //創建套接字---創建飯店
38     sever=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
39     if(sever==INVALID_SOCKET)
40     {
41         WSACleanup();
42         return 1;
43     }
44     /*if(sever=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP)==INVALID_SOCKET)
45     {
46         WSACleanup();
47         return 1;
48     }*///這麽寫會導致綁定失敗？？
49     //綁定---相當於拉客，把客人拉進屋子
50     severaddr.sin_family=AF_INET;
51     severaddr.sin_port=htons(1234);
52     severaddr.sin_addr.S_un.S_addr=inet_addr("192.168.202.1");
53     
54     if(bind(sever,(const sockaddr*)&severaddr,sizeof(severaddr))==SOCKET_ERROR)
55     {
56         WSACleanup();
57         closesocket(sever);
58         return 1;
59     }
　　　　　//監聽----看客人有沒有要點餐的
60     if(listen(sever,4)==SOCKET_ERROR)
61     {
62         WSACleanup();
63         return 1;
64     }
65     printf("等待連接...\n");
66     int clientlen=sizeof(clientaddr);
　　　　//接收
67     waiter=accept(sever,(SOCKADDR*)&clientaddr,&clientlen);//如果有要點餐的，派一個服務員去，將客戶的地址信息傳給店長
68     if(waiter==INVALID_SOCKET)//第一個參數為監聽套接字
69     {
70         printf("接受失敗\n");
71         WSACleanup();
72         closesocket(sever);
73         return 1;
74     }
75     while(1)
76     {
77         char recvbuf[1024]={0};//接受緩沖區
78         char sendbuf[1024]={0};//發送緩沖區
79         if(recv(waiter,recvbuf,sizeof(recvbuf),0)==SOCKET_ERROR)//服務員去負責收客戶信息
80         {                                                       //waiter去收
81             printf("接受數據失敗\n");
82         }
83         printf("%s\n",recvbuf);
84         scanf("%s",sendbuf);
85         send(waiter,(char *)sendbuf,sizeof(sendbuf),0);//waiter去send
86     }
87     WSACleanup();
88     closesocket(sever);
89     closesocket(waiter);
90     return 0;
91 }

客戶端

 1 #include<iostream>
 2 #include <winsock2.h>
 3 
 4 using namespace std;
 5 #pragma comment(lib, "ws2_32.lib")
 6 
 7 int main()
 8 {
 9      WORD wVersionRequested;
10     WSADATA wsaData;
11     int err;
12     wVersionRequested = MAKEWORD(2, 2);
13 
14     err = WSAStartup(wVersionRequested, &wsaData);
15     if (err != 0)
16     {
17                       
18         printf("WSAStartup failed with error: %d\n", err);
19         return 1;
20     }
21 
22     if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 2) 
23     {
24        
25         printf("Could not find a usable version of Winsock.dll\n");
26         WSACleanup();
27         return 1;
28     }
29     else
30         printf("The Winsock 2.2 dll was found okay\n");
31 
32 
33     //創建socket
34     SOCKET sockClient=socket(AF_INET,SOCK_STREAM ,IPPROTO_TCP );
35     if(INVALID_SOCKET ==sockClient)
36     {
37         WSACleanup();
38         return 1;
39     }
40     //連接服務器
41     sockaddr_in  severaddr;
42     severaddr.sin_family=AF_INET;
43     severaddr.sin_port=htons(1234);
44     severaddr.sin_addr.S_un.S_addr=inet_addr("192.168.202.1");
45     if(connect(sockClient,(const sockaddr*)&severaddr,sizeof(severaddr))==SOCKET_ERROR)
46     {//客戶端去連，連接服務器地址
47         WSACleanup();
48         closesocket(sockClient);
49         return 1;
50     }
51     while(1)
52     {
53         char szbuf[1024]={0};
54         cin>>szbuf;
55         send(sockClient,szbuf,sizeof(szbuf),0);//客戶端發送
56         int nReNum=recv(sockClient,szbuf,sizeof(szbuf),0);//客戶端接收
57         if( nReNum>0)
58         {
59             cout<<szbuf<<endl;
60         }
61     }
62     WSACleanup();
63     closesocket(sockClient);
64     return 0;
65 }

TCP客戶端與服務器的實現