tcp_server.cpp

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

int sockfd;

void sig_handler(int signo)
{
    if (signo == SIGINT)
    {
        printf("Server close \n");
        close(sockfd);
        exit(1);
    }
}

//输出连接上来的客户端相关信息
void out_addr(struct sockaddr_in *clientaddr)
{
    //将端口从网络字节序转成主机字节序
    int port = ntohs(clientaddr->sin_port);
    char ip[16];
    memset(ip, 0, sizeof(ip));
    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)
{
    //获取系统时间
    long t = time(0);
    char *s = ctime(&t);
    size_t size = strlen(s) * sizeof(char);
    //将服务器端的系统时间写到客户端
    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("signal sigint error");
        exit(1);
    }

    /*1. 创建socket
     AF_INT:ipv4
     SOCK_STREAM:tcp协议
    */
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0)
    {
        perror("socket error");
        exit(1);
    }

    /*2:调用bind函数绑定socket和地址*/

    struct sockaddr_in serveraddr;
    memset(&serveraddr, 0, sizeof(serveraddr));
    //往地址中填入ip，port，internet类型
    serveraddr.sin_family = AF_INET;            //ipv4
    serveraddr.sin_port = htons(atoi(argv[1])); //htons主机字节序转成网络字节序

    serveraddr.sin_addr.s_addr = INADDR_ANY;

    if (bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0)
    {
        perror("bind error");
        exit(1);
    }

    /*3：调用listen函数监听（指定port监听）
    通知操作系统区接受来自客户顿的连接请求
    第二个参数：指定队列长度
    */

    if (listen(sockfd, 10) < 0)
    {
        perror("listen error");
    }
    std::cout << "I'm listening!" << std::endl;

    /*4：调用accept函数从队列中获得一个客户端的请求连接
    */

    struct sockaddr_in clientaddr;
    socklen_t clientaddr_len = sizeof(clientaddr);

    while (1)
    {

        int fd = accept(sockfd,
                        (struct sockaddr *)&clientaddr,
                        &clientaddr_len);
        pid_t pid = fork();
        if (pid == 0)
        {
            std::cout << "I'm a new process and my pid is " << getpid() << std::endl;
            std::cout << "My parent process's pid is " << getppid() << std::endl;
            if (fd < 0)
            {
                perror("accept error");
                continue;
            }

            /*5：调用IO函数（read/write）和
            连接的客户端进行双向通信
        */
            out_addr(&clientaddr);
            do_service(fd);

            /*6.关闭socket*/
            close(fd);
        }
    }

    return 0;
}