UDP协议详细讲解及C++代码实例

news2025/5/15 4:57:44

一、UDP协议概述

UDP（User Datagram Protocol，用户数据报协议）是一种无连接的、简单的、基于数据报的传输层通信协议。其核心特性包括：

无连接：不需要建立连接即可发送数据。
不可靠：不保证数据包的顺序和到达。
高效：由于没有复杂的连接和可靠性机制，UDP传输效率较高。
适用场景：适用于实时性要求高、可以容忍少量数据丢失的场景，如视频流、实时游戏等。

二、UDP通信流程

1)数据传输

数据被分割为多个UDP数据报，每个数据报独立传输。

2)无连接

通信双方无需建立连接，直接发送和接收数据。

C++代码实例

1. UDP客户端代码（C++）
cpp
#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
 
int main() {
    // 创建UDP套接字
    int client_socket = socket(AF_INET, SOCK_DGRAM, 0);
    if (client_socket == -1) {
        std::cerr << "Failed to create socket." << std::endl;
        return -1;
    }
 
    // 设置服务器地址和端口
    sockaddr_in server_address{};
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(8888);
    server_address.sin_addr.s_addr = inet_addr("127.0.0.1");
 
    try {
        // 发送数据
        const char* message = "Hello, UDP Server!";
        sendto(client_socket, message, strlen(message), 0, (struct sockaddr*)&server_address, sizeof(server_address));
 
        // 接收响应
        char buffer[1024] = {0};
        socklen_t server_address_size = sizeof(server_address);
        int bytes_received = recvfrom(client_socket, buffer, sizeof(buffer), 0, (struct sockaddr*)&server_address, &server_address_size);
        if (bytes_received > 0) {
            std::cout << "Received from server: " << buffer << std::endl;
        }
    } catch (...) {
        std::cerr << "An error occurred during communication." << std::endl;
    }
 
    // 关闭套接字
    close(client_socket);
    return 0;
}

2. UDP服务器端代码（C++）
cpp
#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
 
int main() {
    // 创建UDP套接字
    int server_socket = socket(AF_INET, SOCK_DGRAM, 0);
    if (server_socket == -1) {
        std::cerr << "Failed to create socket." << std::endl;
        return -1;
    }
 
    // 绑定地址和端口
    sockaddr_in server_address{};
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(8888);
    server_address.sin_addr.s_addr = INADDR_ANY;
 
    if (bind(server_socket, (struct sockaddr*)&server_address, sizeof(server_address)) == -1) {
        std::cerr << "Failed to bind socket." << std::endl;
        close(server_socket);
        return -1;
    }
 
    std::cout << "Server is listening on port 8888..." << std::endl;
 
    try {
        while (true) {
            // 接收数据
            char buffer[1024] = {0};
            sockaddr_in client_address{};
            socklen_t client_address_size = sizeof(client_address);
            int bytes_received = recvfrom(server_socket, buffer, sizeof(buffer), 0, (struct sockaddr*)&client_address, &client_address_size);
            if (bytes_received > 0) {
                std::cout << "Received from client: " << buffer << std::endl;
                // 发送响应
                const char* response = "Hello, UDP Client!";
                sendto(server_socket, response, strlen(response), 0, (struct sockaddr*)&client_address, client_address_size);
            }
        }
    } catch (...) {
        std::cerr << "An error occurred in the server loop." << std::endl;
    }
 
    // 关闭套接字
    close(server_socket);
    return 0;
}