C语言理解套接字

痛定思痛。 2022-05-27 02:16 145阅读 0赞

#include<stdio.h>  
    #include<stdlib.h>  
    #include<string.h>  
    #include<errno.h>  
    #include<sys/types.h>  
    #include<sys/socket.h>  
    #include<netinet/in.h>  
    #define DEFAULT_PORT 8000  
    #define MAXLINE 4096  
    int main(int argc, char** argv)  
    {  
        int    socket_fd, connect_fd;  
        struct sockaddr_in     servaddr;  
        char    buff[4096];  
        int     n;  
        //初始化Socket  
        if( (socket_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1 ){  
         printf("create socket error: %s(errno: %d)\n",strerror(errno),errno);  
         exit(0);  
        }  
        else{
        printf("the socket has been created successfully, its id is: %d",socket_fd);
        }
     //初始化  
        memset(&servaddr, 0, sizeof(servaddr));  
        servaddr.sin_family = AF_INET;  
         servaddr.sin_addr.s_addr = htonl(INADDR_ANY);//IP地址设置成INADDR_ANY,让系统自动获取本机的IP地址。  
         servaddr.sin_port = htons(DEFAULT_PORT);//设置的端口为DEFAULT_PORT  
    
    //将本地地址绑定到所创建的套接字上  
        if( bind(socket_fd, (struct sockaddr*)&servaddr, sizeof(servaddr)) == -1){  
            printf("bind socket error: %s(errno: %d)\n",strerror(errno),errno);  
            exit(0);  
        }  
    //开始监听是否有客户端连接  
        if( listen(socket_fd, 10) == -1){  
            printf("listen socket error: %s(errno: %d)\n",strerror(errno),errno);  
            exit(0);  
        }  
        printf("======waiting for client's request======\n");  
        while(1){  
        //阻塞直到有客户端连接，不然多浪费CPU资源。  
        if( (connect_fd = accept(socket_fd, (struct sockaddr*)NULL, NULL)) == -1){  
            printf("accept socket error: %s(errno: %d)",strerror(errno),errno);  
            continue;  
        }  
    //接受客户端传过来的数据  
        n = recv(connect_fd, buff, MAXLINE, 0);  
    //向客户端发送回应数据  
        if(!fork()){ /*紫禁城*/  
        if(send(connect_fd, "Hello,you are connected!\n", 26,0) == -1)  
        perror("send error");  
        close(connect_fd);  
        exit(0);  
        }  
        buff[n] = '\0';  
        printf("recv msg from client: %s\n", buff);  
        close(connect_fd);  
        }  
        close(socket_fd);  
        }

客户机

#include<stdio.h>  
    #include<stdlib.h>  
    #include<string.h>  
    #include<errno.h>  
    #include<sys/types.h>  
    #include<sys/socket.h>  
    #include<netinet/in.h>  
    
    #define MAXLINE 4096  
    
    
    int main(int argc, char** argv)  
    {  
        int    sockfd, n,rec_len;  
        char    recvline[4096], sendline[4096];  
        char    buf[MAXLINE];  
        struct sockaddr_in    servaddr;  
    
    
        if( argc != 2){  
        printf("usage: ./client <ipaddress>\n");  
        exit(0);  
        }  
    
    
        if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0){  
        printf("create socket error: %s(errno: %d)\n", strerror(errno),errno);  
        exit(0);  
        }  
    
    
        memset(&servaddr, 0, sizeof(servaddr));  
        servaddr.sin_family = AF_INET;  
        servaddr.sin_port = htons(8000);  
        if( inet_pton(AF_INET, argv[1], &servaddr.sin_addr) <= 0){  
        printf("inet_pton error for %s\n",argv[1]);  
        exit(0);  
        }  
    
    
        if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0){  
        printf("connect error: %s(errno: %d)\n",strerror(errno),errno);  
        exit(0);  
        }  
    
    
        printf("send msg to server: \n");  
        fgets(sendline, 4096, stdin);  
        if( send(sockfd, sendline, strlen(sendline), 0) < 0)  
        {  
        printf("send msg error: %s(errno: %d)\n", strerror(errno), errno);  
        exit(0);  
        }  
        if((rec_len = recv(sockfd, buf, MAXLINE,0)) == -1) {  
           perror("recv error");  
           exit(1);  
        }  
        buf[rec_len]  = '\0';  
        printf("Received : %s ",buf);  
        close(sockfd);  
        exit(0);  
    }

![这里写图片描述][70]

![这里写图片描述][70 1]

[70]: /images/20220527/a49c80f69a5246a6bd699f85c4b6c8c9.png
[70 1]: /images/20220527/368d8448140a474cad1675b9d6398a24.png