目标

实现客户端连接服务器，通过终端窗口发送信息给服务器端，服务器接收到信息后对信息数据进行回传，客户端读取回传信息并返回。

服务器与客户端通信流程

TCP服务器代码

服务器当前IP地址要知道
建立socket
绑定本地IP地址并设置端口号

#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>

int main()
{
    //socket套接字
    int lfd = socket(AF_INET, SOCK_STREAM, 0);
    if(lfd == -1)
    {
        perror("socket");
        exit(-1);
    }

    //绑定
    struct sockaddr_in saddr;
    saddr.sin_family = AF_INET;
    inet_pton(AF_INET, "192.168.1.108", &saddr.sin_addr.s_addr);
    //saddr.sin_addr.s_addr = INADDR_ANY;//做服务器时表示可以通过任意网卡都可以连接进来
    saddr.sin_port = htons(9999);//转换成网络字节序
    int bindret = bind(lfd, (struct sockaddr *)&saddr, sizeof(saddr));
    if(bindret == -1)
    {
        perror("bind");
        exit(-1);
    }

    //监听
    int ret = listen(lfd, 8);
    if(ret == -1)
    {
        perror("listen");
        exit(-1);
    }

    //等待连接
    struct sockaddr_in clientaddr;
    int len = sizeof(clientaddr);
    int cfd = accept(lfd, (struct sockaddr *)&clientaddr, &len);
    if(cfd == -1)
    {
        perror("accept");
        exit(-1);
    }
    char clientIP[len];
    inet_ntop(AF_INET, &clientaddr.sin_addr, clientIP, len);
    printf("client IP:%s Port:%d\n", clientIP, ntohs(clientaddr.sin_port));
    
    while (1)
    {
        //接收数据
        char rbuf[1024];
        len = read(cfd, rbuf, sizeof(rbuf));
        if(len == -1)
        {
            perror("read");
            exit(-1);
        }
        else if(len == 0)
        {
            printf("Client close...\n");
        }
        else if(len > 0)
        {
            printf("resive data: %s\n", rbuf);
        }

        //发送数据
        char sbuf[] = "i am server\n";
        write(cfd, rbuf, sizeof(rbuf));
    }
    
    

    //关闭连接
    close(cfd);
    close(lfd);

    return 0;
}

TCP客户端代码

知道服务器的IP地址和端口号
然后进行连接

#include <stdio.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>

int main()
{
    //socket套接字
    int lfd = socket(AF_INET, SOCK_STREAM, 0);
    if(lfd == -1)
    {
        perror("socket");
        exit(-1);
    }

    //连接
    struct sockaddr_in saddr;
    saddr.sin_family = AF_INET;
    inet_pton(AF_INET, "192.168.1.108", &saddr.sin_addr.s_addr);
    saddr.sin_port = htons(9999);//转换成网络字节序
    int connect_cont = 3;
    int ret;

jx_connect:
    ret = connect(lfd, (struct sockaddr *)&saddr, sizeof(saddr));
    if(ret == -1)
    {
        perror("connect");
        sleep(2);
        connect_cont--;
        if(connect_cont) goto jx_connect;
        exit(-1);
    }
    printf("client link success!\n");
    //通信
    char rbuf[1024];
    while(1)
    {
        //发送数据
        char sbuf[] = "i am client\n";
        fgets(rbuf, 1024, stdin);
        write(lfd, rbuf, sizeof(rbuf));
        
        //接收数据
        
        int len = read(lfd, rbuf, sizeof(rbuf));
        if(len == -1)
        {
            perror("read");
            exit(-1);
        }
        else if(len == 0)
        {
            printf("Client close...\n");
            break;
        }
        else if(len > 0)
        {
            printf("resive data: %s\n", rbuf);
        }

        sleep(1);
    }
   

    //关闭连接
    close(lfd);

    return 0;
}