基于TCP协议的服务器/客户端编程

socket接口

#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
int socket(int domain, int type, int protocol);
返回：成功返回描述符，失败返回-1

绑定地址，成功返回0，出错返回-1
int bind(int sockfd, const struct sockaddr *addr,
                socklen_t addrlen);
================================
struct sockaddr_in { 
　　 short int sin_family;
　　 unsigned short int sin_port; 
     struct in_addr sin_addr;      
     unsigned char sin_zero[8];
}   

struct in_addr { 
    unsigned long s_addr;
}
================================

查找绑定到套接字的地址，成功返回0，出错返回-1
int getsockname(int sockfd, struct sockaddr *addr, socklen_t *addrlen);

获取对方地址，成功返回0，出错返回-1
int getpeername(int sockfd, struct sockaddr *addr, socklen_t *addrlen);

服务器端：
backlog 指定进行客户端连接排队的队列长度
int listen(int sockfd, int backlog);
int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);

客户端：
int connect(int sockfd, const struct sockaddr *addr,socklen_t addrlen);

TCP/IP编程模型

image.png

基于TCP协议的服务器端

等待客户端连接，返回当前服务器时间给客户端。

#include <arpa/inet.h>
#include <netdb.h>
#include<sys/socket.h>
#include<unistd.h>
#include<string.h>
#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
#include<signal.h>
#include<time.h>

int sockfd;

void sig_handler(int signo) {
    if (signo == SIGINT){
        printf("server close\n");
        /*步骤6：关闭服务器端的socket*/
        close(sockfd);
        exit(1);
    }
}

void out_addr(struct sockaddr_in *clientaddr) {
    //将端口从网络字节序转换成主机字节序
    int port = ntohs(clientaddr->sin_port);
    char ip[16];
    memset(ip, 0, sizeof(ip));
    //将ip地址从网络字节序转换成点分十进制
    inet_ntop(AF_INET, &clientaddr->sin_addr.s_addr, ip, sizeof(ip));
    printf("client:%s(%d) connected\n", ip, port);
}

void do_service(int fd) {
    // 获得系统时间
    long t = time(NULL);
    char *s = ctime(&t);
    size_t size = strlen(s) * sizeof(char);
    if (write(fd, s, size) != size) {
        perror("write error");
    }
}

int main(int argc, char *argv[]) {

    if (argc < 2){
        printf("usage:%s #port\n",argv[0]);
        exit(1);
    }
    
    if (signal(SIGINT, sig_handler) == SIG_ERR){
        perror("signale sigint error");
        exit(1);
    }
    
    /*步骤1：创建socket套接字*/
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0){
        perror("socket error");
        exit(1);
    }
    /*步骤2：调用bind将socket和地址绑定(包括ip，port)*/
    struct sockaddr_in serveraddr;
    memset(&serveraddr, 0, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET; //IPV4
    serveraddr.sin_port = htons(atoi(argv[1]));
    serveraddr.sin_addr.s_addr = INADDR_ANY;
    if(bind(sockfd, (struct sockaddr *)&serveraddr,sizeof(serveraddr)) < 0) {
        perror("bind error");
        exit(1);
    }
    /*步骤3：调用listen函数启动监听(指定port监听)*/
    if(listen(sockfd,10) < 0) {
        perror("listen error");
        exit(1);
    }

    /*步骤4：调用accept函数从队列中获得一个客户端的请求连接
       注意：若没有客户端连接，调用accept函数将阻塞，直到货到衣蛾客户端连接
    */
    struct sockaddr_in clientaddr;
    socklen_t clientaddr_len = sizeof(clientaddr);
    while (1){
        int fd = accept(sockfd,
                        (struct sockaddr *)&clientaddr, 
                        &clientaddr_len);
        if(fd < 0) {
            perror("accept error");
            continue;
        }

        /**
         * 步骤5：调用IO函数(read/write)和连接的客户端进行双向的通信
        */
       out_addr(&clientaddr);
       do_service(fd);
       /*步骤6：关闭客户端的socket*/
       close(fd);
    }
    
    return 0;
}

启动服务器端，监听8888端口

image.png

使用nc命令连接服务器端：

1669857335301.png

##基于TCP协议的客户端

#include <arpa/inet.h>
#include <netdb.h>
#include<sys/socket.h>
#include<unistd.h>
#include<string.h>
#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
#include<signal.h>
#include<time.h>



int main(int argc, char *argv[]) {

    if (argc < 3){
        printf("usage:%s ip port\n",argv[0]);
        exit(1);
    }
    
    /*步骤1：创建socket*/
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0){
        perror("socket error");
        exit(1);
    }

    // 往serveraddr里填入ip，port和地址族类型(ipv4)
    struct sockaddr_in serveraddr;
    memset(&serveraddr, 0, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    serveraddr.sin_port = htons(atoi(argv[2]));
    inet_pton(AF_INET, argv[1], &serveraddr.sin_addr.s_addr);
    /*步骤2：客户端调用connect函数链接到服务器端*/
    if(connect(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0) {
        perror("connect error");
        exit(1);
    }

    /*步骤3：调用IO寒素(read/write)和服务器端双向通信*/
    char buffer[1024];
    memset(buffer, 0 ,sizeof(buffer));
    size_t size;
    if ((size = read(sockfd, buffer, sizeof(buffer))) < 0){
        perror("read error");
    }
    if (write(STDOUT_FILENO, buffer, size) != size){
        perror("write error");
    }

    /*步骤4：关闭socket*/
    close(sockfd);
    return 0;
}