基于TCP协议的socket通信(Linux)

痛定思痛。 2021-12-16 04:16 315阅读 0赞

以下两个程序分别模拟了服务器端和客户端所做的动作: 服务器在和客户端建立连接后, 每1s向客户端发送字符串"a piece of message from server.", 客户端每1s接受一次数据, 并将接收到的数据显示到终端.

我们必须考虑当服务器端先结束运行时, 客户端该做出怎么样的动作: 是继续接收空数据, 还是结束运行. 当然, 客户端应该结束运行, 那么该如何判断服务器端是否结束运行了呢? 在client.c中我加入了对接收数据的长度的判断, 当接收到的数据长度为0时, 那么就结束客户端的运行------这样一来, 客户端便可随服务器端程序的终止而终止了.

//server.c
    #include <stdio.h>
    #include <stdlib.h>
    #include <errno.h>
    #include <string.h>
    #include <sys/types.h>
    #include <netinet/in.h>
    #include <sys/socket.h>
    #include <sys/wait.h>
    #include <arpa/inet.h> 
    #include <unistd.h>
    #define SERVPORT 3333
    #define BACKLOG 10
    
    int sockfd,client_fd;
    int sin_size;
    char buf[50] = "a piece of message from server.";
    
    void send_message()//send pieces of message to host
    {
        while(1)
         {
    	  send(client_fd, buf, 32, 0);
    	  sleep(1);
         }
    }
    
    int main()
    {	
        struct sockaddr_in my_addr;    
        struct sockaddr_in remote_addr; 
        sockfd = socket(AF_INET, SOCK_STREAM, 0);//建立socket --
        my_addr.sin_family=AF_INET;//AF_INET地址族    
        my_addr.sin_port=htons(SERVPORT);//设定端口号(host -> networks)
        my_addr.sin_addr.s_addr = INADDR_ANY;//32位IPv4地址
        bzero(&(my_addr.sin_zero),8); //置前8个字节为0
        if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) 
         {
      	  perror("bind 出错!");		
    	  exit(1);	
         }
        if (listen(sockfd, BACKLOG) == -1) //监听socket连接, 设置队列中最多拥有连接个数为10
         {	
    	  perror("listen 出错!");	
              exit(1);     
         }
        while(1)
         {
    	  sin_size = sizeof(struct sockaddr_in);//记录sockaddr_in结构体所占字节数
    	  if ((client_fd = accept(sockfd, (struct sockaddr *)&remote_addr, &sin_size)) == -1) //accept()缺省是阻塞函数, 阻塞到有连接请求为止
              {	
    	      perror("accept error");		
    	      continue;		
    	  }
    	  printf("收到一个连接来自:  %s\n", inet_ntoa(remote_addr.sin_addr));
    	  if (!fork())//son process 
              { 
    	      send_message();
                close(client_fd);	
                exit(0);		
              }
    	  else//father process 
    	  {
    	     close(client_fd);
      	  }
         }
    }

//client.c
    #include<stdio.h>
    #include <stdlib.h>
    #include <errno.h>
    #include <string.h>
    #include <netdb.h>
    #include <sys/types.h>
    #include <netinet/in.h>
    #include <sys/socket.h>
    #include <arpa/inet.h>
    #define SERVPORT 3333
    #define MAXDATASIZE 100
    
    int sockfd, recvbytes;
    char buf[MAXDATASIZE];
    
    void receive()//receive pieces of message from host
    {
        while(1)
         {
    	  recvbytes = recv(sockfd, buf, MAXDATASIZE,0);
    	  if(recvbytes == 0)
    	  {
    		break;
    	  }
    	  buf[recvbytes] = '\0';//end flag
    	  printf("%s\n", buf);
    	  sleep(1);
         } 
    }
    
    int main(int argc, char *argv[])
    {
        struct hostent *host;
        struct sockaddr_in serv_addr;
        if(argc < 2) 
         {
    	  fprintf(stderr,"Please enter the server's hostname!\n");
    	  exit(1);	
         }
        if((host=gethostbyname(argv[1]))==NULL)
         {
    	  herror("gethostbyname error!");	
    	  exit(1);	
         }
        if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)//建立socket
         { 
    	  perror("socket create error!");	
    	  exit(1);	
         }
        serv_addr.sin_family=AF_INET;
        serv_addr.sin_port=htons(SERVPORT);
        serv_addr.sin_addr = *((struct in_addr *)host->h_addr);
        bzero(&(serv_addr.sin_zero),8);
        if(connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) == -1) //请求连接
         {
    	  perror("connect error!");
    	  exit(1);
         }
        //successful connection
        receive();
        close(sockfd);//关闭连接
    }

运行结果:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70]: /images/20211214/8cce911c17134cf4b862f2fef7c66b77.png