两台ubuntu虚拟机的socket通信讲解

偏执的太偏执、 2021-12-17 01:59 863阅读 0赞

在实验开始前, 我们要准备好两台ubuntu18.04虚拟机, 并在安装完成后将它们开启(主机内存要足够大, 本机内存16G, 在开启两台虚拟机后内存占用已达45%: 若内存较小, 则可将ubuntu虚拟机的内存调为1G或更小, 但会收到较差的使用体验).

注: 下图为两台ubuntu18.04虚拟机已安装好后的情况. 两台ubuntu虚拟机的内存都设为2G, 处理器都为双核(1C2T).

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70][]

接着我们来看一下本题的处理模型.

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 1][]

下面我们来看一下socket通信程序(tcp).

//client.c 客户端
    #include<stdio.h>
    #include <stdlib.h>
    #include <errno.h>
    #include <string.h>
    #include<unistd.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 main(int argc, char *argv[])
    {
        int sockfd, recvbytes;
        char buf[MAXDATASIZE];
        char s[50];
        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
        if((recvbytes=recv(sockfd, buf, MAXDATASIZE, 0)) ==-1)//接收数据 --
         {
    	  perror("connect 出错！");
    	  exit(1);
         }
        buf[recvbytes] = '\0';
        printf("收到: %s",buf);
        //send another piece of message to server
        send(sockfd, "liu", 3, 0);
        //receive a piece of message "Bingo" or "incorrect username" from server
        int nbytes = recv(sockfd, s, 100, 0);
        s[nbytes] = '\0';
        printf("%s", s);
        close(sockfd);//关闭连接 --
    }

//server.c 服务端
    #include<stdio.h>
    #include<stdlib.h>
    #include<errno.h>
    #include<unistd.h>
    #include <string.h>
    #include <sys/types.h>
    #include <netinet/in.h>
    #include <sys/socket.h>
    #include <sys/wait.h>
    #include <arpa/inet.h> 
    #define SERVPORT 3333
    #define BACKLOG 10
    int main()
    {	
        int sockfd,client_fd;
        int sin_size;
        char s[50];
        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()) 
              { 
    		if (send(client_fd, "连接上了 \n", 26, 0) == -1) //--		
    		    perror("send 出错！");	  
    		//receive a piece of message from host
    		int nbytes = recv(client_fd, s, 100, 0);
    		s[nbytes] = '\0';
    		if(s[0] == 'l' && s[1] == 'i' && s[2] == 'u' && nbytes == 3)
    		{
    		     //send the message "Bingo" to host
    		     send(client_fd, "Bingo\n" ,6, 0);
    		}
    		else
    		{
    		     //send the message "incorrect username" to host
    		     send(client_fd, "incorrect username\n", 26, 0);
    		}
                close(client_fd);	
                exit(0);		
              }
    	  close(client_fd);
         }
    }

接下来用第一台ubuntu虚拟机运行服务端程序, 另一台ubuntu虚拟机运行客户端程序.

第一台ubuntu虚拟机运行服务端程序:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 2][]

第二台ubuntu虚拟机运行客户端程序:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 3][]

服务端响应客户端的连接请求, 并显示客户端的IP地址.

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjA0ODQ2Mw_size_16_color_FFFFFF_t_70 4][]

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