socket 编程

1 实现一个 简单的 TCP Server

服务端会相对麻烦一些代码如下：

#include <iostream>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#include <stdlib.h>

#define PORT 8111
#define MESSAGE_LEN 1024
using namespace std;

int main(int arc, char *argv[]) {
    int ret = -1;
    int socket_fd = -1, accept_fd = -1;
    int on = 1;
    int backlog = 10;

    struct sockaddr_in localaddr,remoteaddr;

    char in_buff[MESSAGE_LEN] = {0,};
  
    //创建一个socket
    socket_fd = socket(AF_INET, SOCK_STREAM, 0);
    if (socket_fd == -1) {
        cout << "Failed to create socket!" << endl;
        exit(-1);
    }
		// SO_REUSEADDR 允许套接口和一个已在使用中的地址捆绑
    ret = setsockopt(socket_fd,
                     SOL_SOCKET,
                     SO_REUSEADDR,
                     &on,
                     sizeof(on));
    if (ret == -1) {
        cout << "Failed to set socket options" << endl;
    }
    localaddr.sin_family = AF_INET;
    localaddr.sin_port = PORT;
    localaddr.sin_addr.s_addr = INADDR_ANY;
//    绑定
    ret = bind(socket_fd, (struct sockaddr *) &localaddr, sizeof(struct sockaddr));
    if (ret == -1) {
        cout << "Failed to bind addr!" << endl;
        exit(-1);
    }
//    侦听
    ret = listen(socket_fd, backlog);
    if (ret == -1) {
        cout << " Failed to listen socket!" << endl;
        exit(-1);
    }
    for (;;) {
        socklen_t addr_len = sizeof(struct sockaddr);
        accept_fd = accept(socket_fd,
               (struct sockaddr *) &remoteaddr,
               &addr_len);
//        开始接受数据
        for (;;) {
//            第一个空从accept_fd接受数据，
            ret = recv(accept_fd, (void *) in_buff, MESSAGE_LEN, 0);
            if (ret == 0)//没有发数据和我们断开连接了
            {
                break;
            }
            cout << "rev:" << in_buff << endl;
            send(accept_fd, (void *) in_buff, MESSAGE_LEN, 0);
        }
        close(accept_fd);
    }
//    把socket关闭
    close(socket_fd);
    return 0;
}