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recvfrom() 是一个用于接收来自套接字的数据的函数，通常用于无连接的数据报套接字（如 UDP）
- 简单的 UDP 服务器：
#include<iostream> #include <sys/socket.h> #include <arpa/inet.h> #include <unistd.h> #include <cstring> const int BUFFER_SIZE = 1024; int main() { int sockfd; struct sockaddr_in server_addr, client_addr; socklen_t client_addr_size; char buffer[BUFFER_SIZE]; // 创建套接字 sockfd = socket(AF_INET, SOCK_DGRAM, 0); if (sockfd < 0) { std::cerr << "Error creating socket"<< std::endl; return 1; } // 配置服务器地址 memset(&server_addr, 0, sizeof(server_addr)); server_addr.sin_family = AF_INET; server_addr.sin_addr.s_addr = INADDR_ANY; server_addr.sin_port = htons(8080); // 绑定套接字 if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) { std::cerr << "Error binding socket"<< std::endl; close(sockfd); return 1; } std::cout << "Server listening on port 8080..."<< std::endl; while (true) { // 接收数据 client_addr_size = sizeof(client_addr); ssize_t received = recvfrom(sockfd, buffer, BUFFER_SIZE - 1, 0, (struct sockaddr *)&client_addr, &client_addr_size); if (received < 0) { std::cerr << "Error receiving data"<< std::endl; continue; } buffer[received] = '\0'; std::cout << "Received message: "<< buffer<< std::endl; // 发送响应 sendto(sockfd, "Message received", strlen("Message received"), 0, (struct sockaddr *)&client_addr, client_addr_size); } close(sockfd); return 0; } 这个示例展示了如何使用 recvfrom() 函数创建一个简单的 UDP 服务器。服务器监听端口 8080，接收客户端发送的数据，并向客户端发送确认消息。
- 多线程 UDP 服务器：
#include<iostream> #include <sys/socket.h> #include <arpa/inet.h> #include <unistd.h> #include <cstring> #include<thread> #include <mutex> const int BUFFER_SIZE = 1024; std::mutex mtx; void handle_client(int sockfd, struct sockaddr_in client_addr, socklen_t client_addr_size) { char buffer[BUFFER_SIZE]; while (true) { // 接收数据 ssize_t received = recvfrom(sockfd, buffer, BUFFER_SIZE - 1, 0, (struct sockaddr *)&client_addr, &client_addr_size); if (received < 0) { std::cerr << "Error receiving data"<< std::endl; break; } buffer[received] = '\0'; mtx.lock(); std::cout << "Received message from client: "<< buffer<< std::endl; mtx.unlock(); // 发送响应 sendto(sockfd, "Message received", strlen("Message received"), 0, (struct sockaddr *)&client_addr, client_addr_size); } } int main() { int sockfd; struct sockaddr_in server_addr, client_addr; socklen_t client_addr_size; // 创建套接字 sockfd = socket(AF_INET, SOCK_DGRAM, 0); if (sockfd < 0) { std::cerr << "Error creating socket"<< std::endl; return 1; } // 配置服务器地址 memset(&server_addr, 0, sizeof(server_addr)); server_addr.sin_family = AF_INET; server_addr.sin_addr.s_addr = INADDR_ANY; server_addr.sin_port = htons(8080); // 绑定套接字 if (bind(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) { std::cerr << "Error binding socket"<< std::endl; close(sockfd); return 1; } std::cout << "Server listening on port 8080..."<< std::endl; while (true) { // 等待客户端连接 client_addr_size = sizeof(client_addr); if (recvfrom(sockfd, nullptr, 0, MSG_PEEK, (struct sockaddr *)&client_addr, &client_addr_size) < 0) { std::cerr << "Error waiting for client connection"<< std::endl; continue; } // 为客户端创建新线程 std::thread client_thread(handle_client, sockfd, client_addr, client_addr_size); client_thread.detach(); } close(sockfd); return 0; } 这个示例展示了如何使用 recvfrom() 函数创建一个多线程 UDP 服务器。服务器监听端口 8080，为每个连接的客户端创建一个新线程以处理请求。这样可以同时处理多个客户端请求。
这些示例仅用于说明 recvfrom() 函数在实际项目中的应用。在实际开发中，你可能需要根据项目需求进行更多的错误处理和功能实现。
