如果在线程中执行，简单的 Winsock 服务器将无法工作

Question

我想在一个程序中有多个服务器，但如果我尝试将服务器放在一个函数中并使用线程执行它，它就会崩溃（没有编译错误）。抱歉，代码很长，但需要它来证明我的问题：

#include <winsock2.h>
#include <ws2tcpip.h>
#include <iostream>
#include <Windows.h>
#include <thread>

#pragma comment(lib, "Ws2_32.lib")
#define _WINSOCK_DEPRECATED_NO_WARNINGS

int server()
{
    WSADATA data;
    WSAStartup(MAKEWORD(2, 2), &data);

    sockaddr_in listen_address;
    listen_address.sin_family = AF_INET;
    listen_address.sin_port = htons(1000);
    listen_address.sin_addr.S_un.S_addr = INADDR_ANY;


    SOCKET listen_socket = socket(AF_INET, SOCK_STREAM, 0);

    bind(listen_socket, (sockaddr*)&listen_address, sizeof(listen_address));
    listen(listen_socket, SOMAXCONN);

    sockaddr client_info = { 0 };
    int socklen;
    SOCKADDR_IN addr;
    int addrlen = sizeof(addr);
    listen_socket = accept(listen_socket, (struct sockaddr*)&client_info, &addrlen);

    if (listen_socket != INVALID_SOCKET)
    {
        std::cout << "New connection" << std::endl;
    }

    int iResult, iSendResult;
    char buffer[1024]{ 0 };

    do {
        iResult = recv(listen_socket, buffer, sizeof(buffer), 0);
        if (iResult > 0) {
            std::cout << buffer << std::endl;
        }
        else if (iResult == 0)
            std::cout << "Closing connection" << std::endl;
        else {
            printf("recv failed: %d\n", WSAGetLastError());
            closesocket(listen_socket);
            WSACleanup();
            return 1;
        }

    } while (iResult > 0);

    //clean up
    system("pause");
    closesocket(listen_socket);
    WSACleanup();
    return 0;
}

int main() {
    std::thread server_thread(server);
    return 0;
}

如果你只是运行 server() 函数它工作正常但在一个线程中它崩溃了。

Answer 1

崩溃是因为当 main() 退出时你的 std::thread 超出范围，但你没有在线程上调用 join() 或 detach()，所以std::thread 析构函数正在调用 std::terminate() 终止您的进程。

试试这个：

#include <iostream>
#include <thread>
#include <cstdlib>

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <winsock2.h>
#include <Windows.h>
#include <ws2tcpip.h>

#pragma comment(lib, "Ws2_32.lib")

void server()
{
    int iResult;
    char buffer[1024];

    sockaddr_in listen_address;
    listen_address.sin_family = AF_INET;
    listen_address.sin_port = htons(1000);
    listen_address.sin_addr.S_un.S_addr = INADDR_ANY;

    SOCKET listen_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_socket == INVALID_SOCKET) {
        iResult = WSAGetLastError();
        std::cerr << "socket failed: " << iResult << "\n";
        return;
    }

    if (bind(listen_socket, (sockaddr*)&listen_address, sizeof(listen_address)) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "bind failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    if (listen(listen_socket, 1) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "listen failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    sockaddr client_info = { 0 };
    int socklen;
    int addrlen = sizeof(client_info);

    SOCKET client_socket = accept(listen_socket, (struct sockaddr*)&client_info, &addrlen);
    if (client_socket == INVALID_SOCKET) {
        iResult = WSAGetLastError();
        std::cerr << "accept failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    closesocket(listen_socket);

    std::cout << "New connection" << std::endl;

    do {
        iResult = recv(client_socket, buffer, sizeof(buffer), 0);
        if (iResult <= 0) {
            if (iResult == 0) {
                std::cout << "Closing connection" << std::endl;
            }
            else {
                iResult = WSAGetLastError();
                std::cerr << "recv failed: " << iResult << "\n";
            }
            break;
        }
        std::cout.write(buffer, iResult);
        std::cout << std::endl;
    }
    while (true);

    //clean up
    closesocket(client_socket);
}

int main() {
    WSADATA data;
    int iResult = WSAStartup(MAKEWORD(2, 2), &data);
    if (iResult != 0) {
        std::cerr << "WSAStartup failed: " << iResult << "\n";
        return 0;
    }

    std::thread server_thread(server);

    std::system("pause");
    server_thread.join();

    WSACleanup();
    return 0;
}

现在，每个服务器有 1 个客户端并不是特别有用。要使用 1 个服务器处理多个客户端，您可以在循环中调用 accept()，然后为每个接受的客户端创建一个单独的线程（您可以使用更好的方法，但下面仅用于演示目的），例如：

#include <iostream>
#include <thread>
#include <vector>
#include <atomic>
#include <cstdlib>

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <winsock2.h>
#include <Windows.h>
#include <ws2tcpip.h>

#pragma comment(lib, "Ws2_32.lib")

std::atomic<bool> stopRunning = false;

void client(SOCKET client_socket)
{
    int iResult;
    char buffer[1024];
    fd_set rfds;
    timeval timeout;

    std::cout << "New connection" << std::endl;

    while (!stopRunning.load()) {
        iResult = recv(client_socket, buffer, sizeof(buffer), 0);
        if (iResult == SOCKET_ERROR) {
            iResult = WSAGetLastError();
            if (iResult != WSAEWOULDBLOCK) {
                std::cerr << "recv failed: " << iResult << "\n";
                break;
            }

            FD_ZERO(&rfds);
            FD_SET(client_socket, &rfds);

            timeout.tv_sec = 1;
            timeout.tv_usec = 0;

            iResult = select(0, &rfds, NULL, NULL, &timeout);
            if (iResult < 0) {
                iResult = WSAGetLastError();
                std::cerr << "select failed: " << iResult << "\n";
                break;
            }

            if (iResult == 0)
                continue;
        }
        else if (iResult == 0) {
            std::cout << "Closing connection" << std::endl;
            break;
        }
        else {
            std::cout.write(buffer, iResult);
            std::cout << std::endl;
        }
    }

    //clean up
    closesocket(client_socket);
}

void server()
{
    int iResult;

    sockaddr_in listen_address;
    listen_address.sin_family = AF_INET;
    listen_address.sin_port = htons(1000);
    listen_address.sin_addr.S_un.S_addr = INADDR_ANY;

    SOCKET listen_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_socket == INVALID_SOCKET) {
        iResult = WSAGetLastError();
        std::cerr << "socket failed: " << iResult << "\n";
        return;
    }

    u_long mode = 1;
    if (ioctlsocket(listen_socket, FIONBIO, &mode) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "ioctlsocket failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    if (bind(listen_socket, (sockaddr*)&listen_address, sizeof(listen_address)) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "bind failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    if (listen(listen_socket, SOMAXCONN) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "listen failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    std::vector<std::thread> clients;
    sockaddr client_info;
    int addrlen;
    SOCKET client_socket;
    fd_set rfds;
    timeval timeout;

    while (!stopRunning.load()) {
        FD_ZERO(&rfds);
        FD_SET(listen_socket, &rfds);

        timeout.tv_sec = 1;
        timeout.tv_usec = 0;

        iResult = select(0, &rfds, NULL, NULL, &timeout);
        if (iResult < 0) {
            iResult = WSAGetLastError();
            std::cerr << "select failed: " << iResult << "\n";
            break;
        }

        if (iResult > 0) {
            addrlen = sizeof(client_info);
            client_socket = accept(listen_socket, (struct sockaddr*)&client_info, &addrlen);
            if (client_socket == INVALID_SOCKET) {
                iResult = WSAGetLastError();
                std::cerr << "accept failed: " << iResult << "\n";
                break;
            }

            if (ioctlsocket(client_socket, FIONBIO, &mode) == SOCKET_ERROR) {
                iResult = WSAGetLastError();
                std::cerr << "ioctlsocket failed: " << iResult << "\n";
                closesocket(client_socket);
                continue;
            }

            threads.push_back(std::thread(client, client_socket));
        }
    }

    closesocket(listen_socket);

    stopRunning = true;
    for (auto &t : threads) {
        t.join();
    }    
}

int main() {
    WSADATA data;
    int iResult = WSAStartup(MAKEWORD(2, 2), &data);
    if (iResult != 0) {
        std::cerr << "WSAStartup failed: " << iResult << "\n";
        return 0;
    }

    std::thread server_thread(server);

    std::system("pause");

    stopRunning = true;
    server_thread.join();

    WSACleanup();
    return 0;
}

或者，如果所有套接字都处于非阻塞模式，您根本不需要运行每个客户端都在自己的线程中，例如：

#include <iostream>
#include <thread>
#include <vector>
#include <atomic>
#include <cstdlib>

#define _WINSOCK_DEPRECATED_NO_WARNINGS
#include <winsock2.h>
#include <Windows.h>
#include <ws2tcpip.h>

#pragma comment(lib, "Ws2_32.lib")

std::atomic<bool> stopRunning = false;

void server()
{
    int iResult;

    sockaddr_in listen_address;
    listen_address.sin_family = AF_INET;
    listen_address.sin_port = htons(1000);
    listen_address.sin_addr.S_un.S_addr = INADDR_ANY;

    SOCKET listen_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (listen_socket == INVALID_SOCKET) {
        iResult = WSAGetLastError();
        std::cerr << "socket failed: " << iResult << "\n";
        return;
    }

    u_long mode = 1;
    if (ioctlsocket(listen_socket, FIONBIO, &mode) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "ioctlsocket failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    if (bind(listen_socket, (sockaddr*)&listen_address, sizeof(listen_address)) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "bind failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    if (listen(listen_socket, SOMAXCONN) == SOCKET_ERROR) {
        iResult = WSAGetLastError();
        std::cerr << "listen failed: " << iResult << "\n";
        closesocket(listen_socket);
        return;
    }

    std::vector<SOCKET> clients;
    SOCKET client_socket;
    sockaddr client_info;
    int addrlen;
    fd_set rfds;
    timeval timeout;
    char buffer[1024];

    while (!stopRunning.load()) {
        FD_ZERO(&rfds);
        FD_SET(listen_socket, &rfds);

        for(auto sckt : clients) {
            FD_SET(sckt, &rfds);
        }

        timeout.tv_sec = 1;
        timeout.tv_usec = 0;

        iResult = select(0, &rfds, NULL, NULL, &timeout);
        if (iResult < 0) {
            iResult = WSAGetLastError();
            std::cerr << "select failed: " << iResult << "\n";
            break;
        }

        if (iResult == 0)
            continue;

        if (FD_ISSET(listen_socket, &rfds)) {
            addrlen = sizeof(client_info);
            client_socket = accept(listen_socket, (struct sockaddr*)&client_info, &addrlen);
            if (client_socket == INVALID_SOCKET) {
                iResult = WSAGetLastError();
                std::cerr << "accept failed: " << iResult << "\n";
                break;
            }

            if (ioctlsocket(client_socket, FIONBIO, &mode) == SOCKET_ERROR) {
                iResult = WSAGetLastError();
                std::cerr << "ioctlsocket failed: " << iResult << "\n";
                closesocket(client_socket);
            }
            else {
                std::cout << "New connection" << std::endl;
                clients.push_back(client_socket);
            }
        }

        for (size_t i = 0; i < clients.size();) {
            client_socket = clients[i];

            if (FD_ISSET(client_socket, &rfds)) {
                iResult = recv(client_socket, buffer, sizeof(buffer), 0);
                if (iResult == SOCKET_ERROR) {
                    iResult = WSAGetLastError();
                    std::cerr << "recv failed: " << iResult << "\n";
                    closesocket(client_socket);
                    clients.erase(clients.begin()+i);
                    continue;
                }

                if (iResult == 0) {
                    std::cout << "Closing connection" << std::endl;
                    closesocket(client_socket);
                    clients.erase(clients.begin()+i);
                    continue;
                }

                std::cout.write(buffer, iResult);
                std::cout << std::endl;
            }

            ++i;
        }
    }

    //clean up

    closesocket(listen_socket);

    for (auto sckt : clients) {
        closesocket(sckt);
    }
}

int main() {
    WSADATA data;
    int iResult = WSAStartup(MAKEWORD(2, 2), &data);
    if (iResult != 0) {
        std::cerr << "WSAStartup failed: " << iResult << "\n";
        return 0;
    }

    std::thread server_thread(server);

    std::system("pause");

    stopRunning = true;
    server_thread.join();

    WSACleanup();
    return 0;
}

如果在线程中执行，简单的 Winsock 服务器将无法工作

Simple Winsock server doesn't work if executed in thread

c++

winsock