Linux 下基于 C++ 的 UDP 通信与 Socket 编程实战

地址封装 InetAddr.hpp

#pragma once
#include"Comm.hpp"
#include<iostream>
#include<sys/socket.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<arpa/inet.h>

class InetAddr {
private:
    void PortNet2Host() { _port = ::ntohl(_net_addr.sin_port); }
    void IpNet2Host() {
        char ipbuffer[64];
        const char* ip = inet_ntop(AF_INET, &_net_addr.sin_addr, ipbuffer, sizeof(ipbuffer));
        (void)ip;
    }
public:
    InetAddr() {}
    // 网络转点分十进制
    InetAddr(const struct sockaddr_in& addr):_net_addr(addr){
        PortNet2Host();
        IpNet2Host();
    }
    InetAddr(uint16_t port):_port(port),_ip(""){
        _port = _net_addr.sin_family = AF_INET;
        _net_addr.sin_port = htons(_port);
        _net_addr.sin_addr.s_addr = INADDR_ANY;
    }
    struct sockaddr* NetAddr() { return CONV(&_net_addr); }
    socklen_t NetAddrLen() { return sizeof(_net_addr); }
    std::string Ip() { return _ip; }
    std::uint16_t Port() { return _port; }
    ~InetAddr() {}
private:
    struct sockaddr_in _net_addr;
    uint16_t _port;
    std::string _ip;
};

服务器核心 UdpServer.hpp

#ifndef __UDP_SERVER_HPP__
#define __UDP_SERVER_HPP__
#include"InetAddr.hpp"
#include"Comm.hpp"
#include<iostream>
#include<string>
#include<memory>
#include<sys/socket.h>
#include<sys/types.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<strings.h>
#include<string.h>
#include"Log.hpp"
using namespace lyrics;

const static int gsockfd = -1;
const static std::string gdefaultip = "127.0.0.1";
const static uint16_t defaultport = 8000;

class UdpServer {
public:
    UdpServer(uint16_t port = defaultport):_sockfd(gsockfd),_addr(port),_isrunning(false) {}

    void InitServer() {
        _sockfd = socket(AF_INET, SOCK_DGRAM, 0);
        if (_sockfd < 0) {
            LOG(LogLevel::FATAL) << "socket: " << strerror(errno);
            Die(SOCKET_ERR);
        }
        LOG(LogLevel::INFO) << "socket success, sockfd is: " << _sockfd;
        int n = ::bind(_sockfd, _addr.NetAddr(), _addr.NetAddrLen());
        if (n < 0) {
            LOG(LogLevel::FATAL) << "socket: " << strerror(errno);
            Die(BIND_ERR);
        }
        LOG(LogLevel::INFO) << "bind success";
    }

    void Start() {
        _isrunning = true;
        while (true) {
            struct sockaddr_in peer;
            socklen_t len = sizeof(peer);
            char inbuffer[1024];
            ssize_t n = ::recvfrom(_sockfd, inbuffer, sizeof(inbuffer)-1, 0, CONV(&peer), &len);
            if (n > 0) {
                InetAddr cli(peer);
                inbuffer[n] = 0;
                std::string clientinfo = cli.Ip() + ":" + std::to_string(cli.Port()) + " # " + inbuffer;
                LOG(LogLevel::DEBUG) << clientinfo;
                std::string echo_string = "echo ";
                echo_string += inbuffer;
                ::sendto(_sockfd, echo_string.c_str(), echo_string.size(), 0, CONV(&peer), sizeof(peer));
            }
        }
        _isrunning = false;
    }

    ~UdpServer() {
        if (_sockfd > gsockfd) ::close(_sockfd);
    }
private:
    int _sockfd;
    InetAddr _addr;
    bool _isrunning;
};
#endif

服务器入口 UdpServer.cc

#include"UdpServer.hpp"
int main(int argc, char* argv[]) {
    if (argc != 2) {
        std::cerr << "Usage" << argv[0] << "localport" << std::endl;
        Die(USAGE_ERR);
    }
    ENABLE_CONSOLE_LOG();
    std::unique_ptr<UdpServer> svr_uptr = std::make_unique<UdpServer>(std::stoi(argv[1]));
    svr_uptr->InitServer();
    svr_uptr->Start();
    return 0;
}

客户端

客户端逻辑相对简单，创建套接字后向目标 IP 和端口发送数据即可。为了模拟交互，客户端会写入死循环，发送消息并等待服务器的回显。

#include"UdpClient.hpp"
#include"Comm.hpp"
#include<iostream>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<string.h>
#include<cstdlib>
#include<string>

int main(int argc, char* argv[]) {
    if (argc != 3) {
        std::cerr << "Usage" << argv[0] << "serverip serverport" << std::endl;
        Die(USAGE_ERR);
    }
    std::string serverip = argv[1];
    uint16_t serverport = std::stoi(argv[2]);

    int sockfd = ::socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        std::cerr << "socket error" << std::endl;
        Die(SOCKET_ERR);
    }

    struct sockaddr_in server;
    memset(&server, 0, sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(serverport);
    server.sin_addr.s_addr = ::inet_addr(serverip.c_str());

    while (true) {
        std::cout << "please Enter: ";
        std::string message;
        std::getline(std::cin, message);
        int n = ::sendto(sockfd, message.c_str(), message.size(), 0, CONV(&server), sizeof(server));
        (void)n;

        struct sockaddr_in temp;
        socklen_t len = sizeof(temp);
        char buffer[1024];
        n = ::recvfrom(sockfd, buffer, sizeof(buffer)-1, 0, CONV(&temp), &len);
        if (n > 0) {
            buffer[n] = 0;
            std::cout << buffer << std::endl;
        }
    }
    return 0;
}

总结

至此，我们用 C++ 完整实现了一个基于 UDP 的通信流程。从创建 socket、绑定地址，到收发数据，每一步都围绕 Linux 下的 socket 编程核心展开。虽然 UDP 天生无连接且不可靠，但正因如此，它在低延迟、高并发场景下依然扮演着重要角色。希望这篇内容帮你理清了 UDP 的基本用法，也为后续深入网络编程打下了基础。