【Linux系统编程】TCP实现--socket

使用套接字socket实现服务器和客户端之间的TCP通信。

流程如下：

实现代码：

c 复制代码

/* server.c */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <errno.h>
#include <ctype.h>

#define SERV_PORT 9527

void sys_err(const char *str)
{
    perror(str);
    exit(1);
}


int main(int argc, char *argv[])
{
    struct sockaddr_in serv_addr, client_addr;
    socklen_t client_addr_len;
    char buf[BUFSIZ], client_IP[1024];
    //1. 创建监听套接字
    int lfd = socket(AF_INET,  //IPV4
                    SOCK_STREAM, 
                    0);
    if(lfd == -1) //check RETURN VALUE
    {
        sys_err("socket error");
    }
    //2. 绑定本地的IP地址和端口号
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(SERV_PORT);
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);

    int ret = bind(lfd,  (struct sockaddr *)&serv_addr, sizeof(serv_addr));
    if(ret == -1)
    {
        sys_err("bind error");
    }

    //3. 设置监听
    int ret_listen = listen(lfd, 128);
    if(ret_listen == -1)
    {
        sys_err("listen error");
    }
    
    //4. 阻塞等待，连接的到达，连接成功后返回通信用的套接字
    client_addr_len = sizeof(client_addr);
    int cfd = accept(lfd, (struct sockaddr*)&client_addr, &client_addr_len);
    if(cfd == -1)
    {
        sys_err("accept error");
    }
    printf("client ip is %s, port is %d\n",
             inet_ntop(AF_INET, &client_addr.sin_addr.s_addr, client_IP, sizeof(client_IP)),
             ntohs(client_addr.sin_port));

    //5. 开始通信
    while(1)
    {
        ssize_t ret_acc = read(cfd, buf, sizeof(buf));
        write(STDOUT_FILENO, buf, ret_acc);

        for(int i = 0; i < ret_acc; i++)
        {
            buf[i] = toupper(buf[i]);
        }
        write(cfd, buf, ret_acc);
    }

    close(lfd);
    close(cfd);

    return 0;
}

c 复制代码

/* client.c */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <errno.h>
#include <ctype.h>

#define SERV_PORT 9527

void sys_err(const char *str)
{
    perror(str);
    exit(1);
}


int main(int argc, char *argv[])
{
    int cfd;
    struct sockaddr_in serv_addr;
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(SERV_PORT);
    inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr.s_addr);
    char buf[BUFSIZ];
    int cnt = 10;

    //1. 创建监听套接字
    cfd = socket(AF_INET, SOCK_STREAM, 0);
    if(cfd == -1) 
    {
        sys_err("socket error");
    }

    int ret = connect(cfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
    if(ret != 0)
    {
        sys_err("connect error");
    }

    while(cnt--)
    {
        write(cfd, "hello\n", 6);
        ret = read(cfd, buf, sizeof(buf));
        write(STDERR_FILENO, buf, ret);
        sleep(1);

    }

    close(cfd);

    return 0;
}

实验现象

客户端向服务器发送10次hello，接收到服务器发来的10次大写HELLO；服务器首先打印IP地址和端口号，随后打印收到的10次由客户端传来的hello。