C++ recvfrom函数在实际项目中的应用案例

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。