Socket库在C++中的多线程应用

在C++中，使用Socket库进行多线程应用开发时，需要注意线程安全和资源管理。以下是一个简单的示例，展示了如何在多线程环境中使用Socket库进行通信。

首先，需要包含必要的头文件并创建一个基本的Socket服务器：

#include <iostream>
#include <thread>
#include <mutex>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>

std::mutex mtx;

void handle_client(int client_socket) {
    char buffer[1024] = {0};
    while (true) {
        int len = recv(client_socket, buffer, sizeof(buffer) - 1, 0);
        if (len <= 0) {
            break;
        }
        std::lock_guard<std::mutex> lock(mtx);
        std::cout << "Received from client: " << buffer << std::endl;
        send(client_socket, buffer, len, 0);
    }
    close(client_socket);
}

int main() {
    int server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket == -1) {
        std::cerr << "Error creating socket" << std::endl;
        return 1;
    }

    struct sockaddr_in server_addr;
    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);

    if (bind(server_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        std::cerr << "Error binding socket" << std::endl;
        return 1;
    }

    if (listen(server_socket, 3) == -1) {
        std::cerr << "Error listening on socket" << std::endl;
        return 1;
    }

    while (true) {
        struct sockaddr_in client_addr;
        socklen_t client_addr_len = sizeof(client_addr);
        int client_socket = accept(server_socket, (struct sockaddr *)&client_addr, &client_addr_len);
        if (client_socket == -1) {
            std::cerr << "Error accepting client connection" << std::endl;
            continue;
        }

        std::thread client_thread(handle_client, client_socket);
        client_thread.detach();
    }

    close(server_socket);
    return 0;
}

在这个示例中，我们创建了一个简单的Socket服务器，监听8080端口。当客户端连接时，服务器会创建一个新线程来处理客户端的请求。我们使用std::mutex来确保在多线程环境下对共享资源（如std::cout）的安全访问。

客户端可以使用以下代码连接到服务器并发送接收消息：

#include <iostream>
#include <thread>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>

void handle_client() {
    int client_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (client_socket == -1) {
        std::cerr << "Error creating socket" << std::endl;
        return;
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    server_addr.sin_port = htons(8080);

    if (connect(client_socket, (struct sockaddr *)&server_addr, sizeof(server_addr)) == -1) {
        std::cerr << "Error connecting to server" << std::endl;
        return;
    }

    std::string message = "Hello, server!";
    send(client_socket, message.c_str(), message.size(), 0);
    char buffer[1024] = {0};
    int len = recv(client_socket, buffer, sizeof(buffer) - 1, 0);
    std::cout << "Received from server: " << buffer << std::endl;

    close(client_socket);
}

int main() {
    std::thread client_thread(handle_client);
    client_thread.join();
    return 0;
}

这个示例展示了如何在多线程环境中使用Socket库进行简单的客户端和服务器通信。请注意，这个示例仅用于演示目的，实际应用中可能需要处理更多的错误情况和边缘情况。