如图：四次挥手，关闭函数，作用：

#if 0//-----2--TCP并发服务器--------//
        //----- ----------//
int main()
{
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd<0)
    {
        printf("socket error\n");
        return 0;
    }

    //设置端口复用
	int yes=1;
	setsockopt(sockfd, SOL_SOCKET,SO_REUSEADDR,&yes, sizeof(yes));

    struct sockaddr_in my_addr;
    bzero(&my_addr, sizeof(my_addr));

    //服务器绑定
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(9000);
    my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    bind(sockfd, (struct sockaddr *)&my_addr, sizeof(my_addr));    




    //监听客户
    listen(sockfd, 20);

    //保存链接的客户端的
    struct sockaddr_in cli_addr;
    socklen_t len = sizeof(cli_addr);
    //保存服务器接收到的信息
    char buf[128] = "";
    //与客户端通信的临时套接字
    int sockfd_new;
    //保存客户端的点分十进制
    char ip[16] = "";
    pid_t pid;
    while(1)
    {
        sleep(1);

        bzero(&cli_addr, sizeof(cli_addr));

        sockfd_new = accept(sockfd,(struct sockaddr *)&cli_addr, &len );


        pid = fork();
        if(pid < 0)
        {
            return;
        }
        else if(pid == 0)
        {
            close(sockfd);

            inet_ntop(AF_INET, &cli_addr.sin_addr.s_addr, ip, 16);
            printf("子进程中 IP %s 已连接服务器\n",ip);

            while(1)
            {
                memset(buf, 0, sizeof(buf));
                recv(sockfd_new, buf, sizeof(buf), 0);
                printf("收到--buf----%s \n",buf);
                send(sockfd_new, buf, strlen(buf), 0);

                if(strncmp(buf, "bye", 3) == 0  || strlen(buf) == 0)
                {               
                    break;                   
                }
            }

            printf("子进程中 IP %s 已断开服务器\n",ip);
            close(sockfd_new);  
            exit(0);
        }
        else
        {
            close(sockfd_new);
            //父子进程中的内容一样的，父进程同样需要关闭，结束的临时套接字
            //然后在返回监听
            //wait(NULL);
        }
    }


    close(sockfd);
    return 0;
}
#endif