c++ - 多连接套接字c++

Question

我正在尝试实现我自己的服务器端和客户端，它们使用套接字发送和接收数据。但是我在实现多线程方面遇到了一些问题。我的server.cpp:

#include <iostream>
#include <netinet/in.h>
#include <cstring>
#include <arpa/inet.h>
#include <unistd.h>
#include <thread>
using namespace std;

void connection_handler(int socket) {
    char client_message[256];
    memset(&client_message, 0, 256);
    size_t message_size = 0;

    while ((message_size = recv(socket, client_message, sizeof(client_message) - 1, 0)) > 0) {
        client_message[message_size] = '\0';
        cout << "[Server] Client message accepted" << endl;
        cout << "[Server] Client message: " << client_message << endl;

        if (write(socket, client_message, message_size) == -1) {
            cout << "[Client] Message sending failed" << endl;
            return;
        }
        cout << "[Server] Message sent to client" << endl << endl;
        cout << "============================" << endl << endl;
        cout.flush();

        memset(&client_message, 0, 256);
    }
}

int main() {
    unsigned short int PORT = 8080;
    int listener, client_socket;
    socklen_t client_len;

    struct sockaddr_in server_address{};

    memset(&server_address, 0, sizeof(server_address));

    listener = socket(AF_INET, SOCK_STREAM, 0);

    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(PORT);
    if (inet_aton("127.0.0.1", &server_address.sin_addr) == 0) {
        cout << "[Server] Invalid IP address" << endl;
        return -1;
    }

    if (bind(listener, (struct sockaddr*) &server_address, sizeof(server_address)) == -1) {
        cout << "[Server] Binding failed" << endl;
        return -1;
    }
    cout << "[Server] All setting are done" << endl;
    cout << "[Server] Server enabled" << endl;

    if (listen(listener, 100) == -1) {
        cout << "[Server] Listening failed" << endl;
        return -1;
    }
    cout << "[Server] Waiting for connection..." << endl;

    for (; ;) {
        client_socket = accept(listener, (struct sockaddr*) &server_address, &client_len);
        cout << "[Server] Connection accepted" << endl << endl;
        cout << "----------------------------" << endl << endl;

        int new_socket = client_socket;

        thread handling_thread(connection_handler, new_socket);
        handling_thread.detach();
    }
}

我的client.cpp:

#include <iostream>
#include <netinet/in.h>
#include <cstring>
#include <arpa/inet.h>
#include <unistd.h>
using namespace std;

int main() {
    unsigned short int PORT = 8080;
    int sockfd;
    char buffer[256] = {0};
    struct sockaddr_in server_address{};

    sockfd = socket(AF_INET, SOCK_STREAM, 0);

    memset(&server_address, '0', sizeof(server_address));
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(PORT);
    server_address.sin_addr.s_addr = INADDR_ANY;

    if (connect(sockfd, (struct sockaddr*) &server_address, sizeof(server_address)) < 0) {
        cout << "[Client] Connection failed" << endl;
        return -1;
    }
    cout << "[Client] All setting are done" << endl;
    cout << "[Client] Succefully connected to server" << endl << endl;
    cout << "----------------------------" << endl << endl;

    while (true) {
        string client_request;
        cout << "[Client] Enter a message: ";
        getline(cin, client_request);

        if (client_request == "-1") {
            write(sockfd, client_request.c_str(), client_request.size());
            close(sockfd);
            cout << endl << "[Client] Client exited" << endl;
            return 0;
        }

        if (write(sockfd, client_request.c_str(), client_request.size()) == -1) {
            cout << "[Client] Message sending failed" << endl;
        }
        cout << "[Client] Message sent to server" << endl;

        memset(&buffer, 0, 256);
        read(sockfd, buffer, 256);

        cout << "[Client] Server message: " << buffer << endl << endl;
        cout << "============================" << endl << endl;
        cout.flush();
    }
}

在我再创建一个到服务器的连接之前它一直工作正常，然后第二个客户端可以发送和接收数据，但是此时第一个变得不工作了。我这样编译我的程序:g++ server.cpp -lpthread -o server -std=c++11 然后在其他控制台选项卡中运行我编译的 client.cpp:./client。为了检查多线程工作，我再次运行客户端(再次在另一个选项卡中)并尝试同时在两个选项卡中发送请求。我想在我的程序中实现多线程。我该怎么做？

UPD:我正在使用 Linux

UPD2:问题已解决。固定代码。

Answer 1

    int new_socket = client_socket;

    thread handling_thread(connection_handler, &new_socket);
    handling_thread.detach();
}

这会初始化 new_socket，它会在此 for 循环内的本地范围内声明，然后将指向此 new_socket 的指针传递给开始的新线程，然后分离。紧随其后，此 for 循环迭代结束，这会在开始此循环的下一次迭代之前销毁 new_socket 对象。

与此同时，执行线程反复尝试取消引用它接收到的 int *，它现在指向一个已销毁的对象。这会导致未定义的行为，并且可能是您的程序“不工作”的原因。

最简单的解决方案是使用new 在动态范围内创建int 套接字值，然后将指针传递给这个new ed 套接字值到执行线程。当然，执行线程将负责检索套接字值，然后适本地删除它，以避免内存泄漏。

对于这个简单的程序来说，这应该足够了。为了可靠性，更复杂的程序可能需要稍微复杂一些的套接字和动态范围处理逻辑。