Socket庫在C++中的多線程應用

在C++中，使用Socket庫進行多線程應用開發時，需要注意線程安全和資源管理。以下是一個簡單的示例，展示了如何在多線程環境中使用Socket庫進行通信。

首先，需要包含必要的頭文件并創建一個基本的Socket服務器：

#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;
}

在這個示例中，我們創建了一個簡單的Socket服務器，監聽8080端口。當客戶端連接時，服務器會創建一個新線程來處理客戶端的請求。我們使用std::mutex來確保在多線程環境下對共享資源（如std::cout）的安全訪問。

客戶端可以使用以下代碼連接到服務器并發送接收消息：

#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;
}

這個示例展示了如何在多線程環境中使用Socket庫進行簡單的客戶端和服務器通信。請注意，這個示例僅用于演示目的，實際應用中可能需要處理更多的錯誤情況和邊緣情況。