ECHO网络程序的演变史 (2) --- TCP Echo

Andrew Haung

 

 

一.TCP编程流程

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 服务器编程流程

 

 客户端编程流程

      

 

二.TCP Echo实现代码

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服务器代码 tcp_echo_svr.c

 

 

/*
  TCP Echo Server 
  Author :Andrew Huang
 
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>


#include <stdio.h>
#include <string.h>


int main(int argc ,char * argv[])
{
  unsigned short port = 9000;
   
   int listen_fd ;
   int client_fd;

   struct sockaddr_in addr; //ipv4的地址结构

   struct sockaddr_in client_addr ;
   socklen_t addr_len;

    char buf[1024];
   int len ;
  
   if(argc >1)
     {
         port = (unsigned short)atoi(argv[1]);
     }

  //第一步：创建一个IPV4,TCP，可以运行所有协议的SOCKET

  listen_fd = socket(PF_INET,SOCK_STREAM,0);
  if(listen_fd == -1)
   {
        perror("socket");
         return -1;
   }


   //第二步:用bind来指定端口

   memset(&addr,0,sizeof(addr));
    addr.sin_port = htons(port); //转成网络序的端口

   addr.sin_family = AF_INET; //ipv4的地址类型

   //addr.sin_addr.s_addr = inet_addr("0.0.0.0"); //bind 的sin_addr表示在哪一个网卡上有效,

   //绑定在0.0.0.0上表示这个SOCKET在所有网卡侦听

   addr.sin_addr.s_addr = INADDR_ANY; //INADDR_ANY = 0 = inet_addr("0.0.0.0")


    if(bind(listen_fd,(const struct sockaddr *)&addr,sizeof(addr)) == -1)
       {
          perror("bind");
            close(listen_fd);
          return -2;
       }

   //第三步： 通知内核里的TCP／IP协议栈，让这个SOCKET开始侦听网络上的请求

   // listen只是通知一下，通知成功立即执行后面代码

     if(listen(listen_fd,20) == -1)
       {
             perror("listen");
        close(listen_fd);
             return -3;
       }


      fprintf(stdout,"TCP Echo Server listen on %d\n",port);
   
      
     while(1)
       {
           memset(&client_addr,0,sizeof(client_addr));
           client_addr.sin_family = AF_INET;
           addr_len = sizeof(client_addr); //必须赋值！


           //第四步：服务器在侦听客户端请求

                printf("accept client ...\n");
           client_fd = accept(listen_fd,(struct sockaddr *)&client_addr,&addr_len);
             if(client_fd == -1)
               {
                  perror("accept");
                     continue;
               }

             fprintf(stdout,"client socket %d,addr %s,port %d\n",client_fd,
                    inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port));

             //第五步：与客户端在新的socket进行通讯

             //注意，是从client_fd,

               len = recv(client_fd,buf,sizeof(buf),0);
                  if(len <= 0)
                           continue;
                  
                  buf[len] = 0;
                  fprintf(stdout,"RECV:\"%s\"\n",buf);
                  
              //第六步：用send把数据照原样发给客户端

                   send(client_fd,buf,len,0);

                close(client_fd);
       }

     printf("exit");
      close(listen_fd);

}


客户端代码 tcp_echo_cli.c

 

/*
  TCP Echo Client
 
   Author :Andrew Huang

 */

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include <stdio.h>
#include <string.h>


int main(int argc ,char * argv[])
{
   unsigned short port = 9000;
   
   int sock ;
    char ipaddr[32] = "127.0.0.1";
    char buf[32] = "hello server";
    struct sockaddr_in serv_addr;
    int len;

     if(argc >1)
     {
         port = (unsigned short)atoi(argv[1]);
     }

    if(argc >2)
     {
          memset(ipaddr,0,sizeof(ipaddr));
         strncpy(ipaddr,argv[2],sizeof(ipaddr)-1);
     }

    if(argc > 3)
       {
            memset(buf,0,sizeof(buf));
         strncpy(buf,argv[3],sizeof(buf)-1);
        }


   printf("connect server %s:%d,buf %s\n",ipaddr,port,buf);

  //第一步：创建一个IPV4,TCP，可以运行所有协议的SOCKET

   sock = socket(PF_INET,SOCK_STREAM,0);
   if(sock == -1)
      {
          perror("socket");
          return -1;
      }


    //第二步:对于客户端,port可用任意一个编号,如果不使用bind，协议栈会自动分配没用的端口0

    // 省略bind ....


   //第三步：用connect()去联接服务器

    memset(&serv_addr,0,sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(port);
    serv_addr.sin_addr.s_addr = inet_addr(ipaddr);
 
     //printf("ipaddr %s,s_addr %x\n",ipaddr,ntohl( serv_addr.sin_addr.s_addr));


     if(connect(sock,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) == -1)
        {
            perror("connect");
              close(sock);
              return -2;
        }
#if 1 /* socket扩展 */
     {//可以从socket取到自己所绑定的端口和地址

      socklen_t addr_len;
     memset(&serv_addr ,0 ,sizeof(serv_addr));
                 addr_len = sizeof(serv_addr);
             getsockname(sock,(struct sockaddr *)&serv_addr,&addr_len);
           
           fprintf(stdout,"local addr %s ,port %d\n",inet_ntoa(serv_addr.sin_addr),ntohs(serv_addr.sin_port));

      

   //扩展3:使用getpeername，根据socket查出对端的地址的端口.

              memset(&serv_addr ,0 ,sizeof(serv_addr));
                 addr_len = sizeof(serv_addr);
             getpeername(sock,(struct sockaddr *)&serv_addr,&addr_len);
           
           fprintf(stdout,"peer addr %s ,port %d\n",inet_ntoa(serv_addr.sin_addr),ntohs(serv_addr.sin_port));

}

#endif
        if(send(sock,buf,strlen(buf)+1,0)<= 0)
           {
               perror("send");
              close(sock);
              return -3;
           }

           len = recv(sock,buf,sizeof(buf),0);
           if(len >0)
             {
                 buf[len] = 0;
                 printf("SERVER:%s\n",buf);
             }

              //关闭socket

            close(sock);
           
   
}