TCP客户端与服务器的实现

为了更容易理解，我们举一个小例子来说明服务器与客户端之间的连接过程。

有一个饭店，饭店里有服务员，服务员用于招待客人

特别要注意的是：要记住相关函数的各个参数都是什么，什么时候返回SOCKET_ERROR,什么时候返回INVALID_SOCKET

服务器

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

 int main()
 {
     //初始化wsa
     WORD wVersionRequested;
     WSADATA wsaData;
     int err;
     wVersionRequested = MAKEWORD(, );

     err = WSAStartup(wVersionRequested, &wsaData);
     if (err != )
     {

         printf("WSAStartup failed with error: %d\n", err);
         return ;
     }

     if (LOBYTE(wsaData.wVersion) !=  || HIBYTE(wsaData.wVersion) != )
     {

         printf("Could not find a usable version of Winsock.dll\n");
         WSACleanup();
         return ;
     }
     else
         printf("The Winsock 2.2 dll was found okay\n");

     SOCKET sever;
     SOCKET waiter;//服务员用于招待客人
     struct sockaddr_in severaddr;
     struct sockaddr_in clientaddr;     //创建套接字---创建饭店
     sever=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
     if(sever==INVALID_SOCKET)
     {
         WSACleanup();
         return ;
     }
     /*if(sever=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP)==INVALID_SOCKET)
     {
         WSACleanup();
         return 1;
     }*///这么写会导致绑定失败？？
     //绑定---相当于拉客，把客人拉进屋子
     severaddr.sin_family=AF_INET;
     severaddr.sin_port=htons();
     severaddr.sin_addr.S_un.S_addr=inet_addr("192.168.202.1");

     if(bind(sever,(const sockaddr*)&severaddr,sizeof(severaddr))==SOCKET_ERROR)
     {
         WSACleanup();
         closesocket(sever);
         return ;
     }
　　　　　//监听----看客人有没有要点餐的
     if(listen(sever,)==SOCKET_ERROR)
     {
         WSACleanup();
         return ;
     }
     printf("等待连接...\n");
     int clientlen=sizeof(clientaddr);
　　　　//接收
     waiter=accept(sever,(SOCKADDR*)&clientaddr,&clientlen);//如果有要点餐的，派一个服务员去，将客户的地址信息传给店长
     if(waiter==INVALID_SOCKET)//第一个参数为监听套接字
     {
         printf("接受失败\n");
         WSACleanup();
         closesocket(sever);
         return ;
     }
     while()
     {
         char recvbuf[]={};//接受缓冲区
         char sendbuf[]={};//发送缓冲区
         if(recv(waiter,recvbuf,sizeof(recvbuf),)==SOCKET_ERROR)//服务员去负责收客户信息
         {                                                       //waiter去收
             printf("接受数据失败\n");
         }
         printf("%s\n",recvbuf);
         scanf("%s",sendbuf);
         send(waiter,(char *)sendbuf,sizeof(sendbuf),);//waiter去send
     }
     WSACleanup();
     closesocket(sever);
     closesocket(waiter);
     return ;
 }

客户端

 #include<iostream>
 #include <winsock2.h>

 using namespace std;
 #pragma comment(lib, "ws2_32.lib")

 int main()
 {
      WORD wVersionRequested;
     WSADATA wsaData;
     int err;
     wVersionRequested = MAKEWORD(, );

     err = WSAStartup(wVersionRequested, &wsaData);
     if (err != )
     {

         printf("WSAStartup failed with error: %d\n", err);
         return ;
     }

     if (LOBYTE(wsaData.wVersion) !=  || HIBYTE(wsaData.wVersion) != )
     {

         printf("Could not find a usable version of Winsock.dll\n");
         WSACleanup();
         return ;
     }
     else
         printf("The Winsock 2.2 dll was found okay\n");

     //创建socket
     SOCKET sockClient=socket(AF_INET,SOCK_STREAM ,IPPROTO_TCP );
     if(INVALID_SOCKET ==sockClient)
     {
         WSACleanup();
         return ;
     }
     //连接服务器
     sockaddr_in  severaddr;
     severaddr.sin_family=AF_INET;
     severaddr.sin_port=htons();
     severaddr.sin_addr.S_un.S_addr=inet_addr("192.168.202.1");
     if(connect(sockClient,(const sockaddr*)&severaddr,sizeof(severaddr))==SOCKET_ERROR)
     {//客户端去连，连接服务器地址
         WSACleanup();
         closesocket(sockClient);
         return ;
     }
     while()
     {
         char szbuf[]={};
         cin>>szbuf;
         send(sockClient,szbuf,sizeof(szbuf),);//客户端发送
         int nReNum=recv(sockClient,szbuf,sizeof(szbuf),);//客户端接收
         if( nReNum>)
         {
             cout<<szbuf<<endl;
         }
     }
     WSACleanup();
     closesocket(sockClient);
     return ;
 }