簡單的非阻塞多線程tcp服務器

Question

我正在學習C ++，本周末我開始使用套接字和線程。 Bellow是一個簡單的多線程服務器，我根據一些教程制作。

我面臨的問題是，當我與2個telnet客戶端連接時，只有第一個連接的擊鍵出現在服務器上。 第一個telnet連接關閉后，第二個telnet連接發送的任何鍵擊突然出現。 有人可以向我解釋我在這里做錯了什么嗎？

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

#pragma comment (lib, "ws2_32.lib")

void clientSocketHandler(SOCKET clientSocket, std::string client_ip) {

    char buf[4096];

    std::thread::id thread_id = std::this_thread::get_id();
    std::cout << thread_id << " - " << client_ip << ": connected" << std::endl;

    while (true)
    {

        ZeroMemory(buf, 4096);

        int bytesReceived = recv(clientSocket, buf, 4096, 0);

        if (bytesReceived == 0)
        {

            std::cout << thread_id << " - " << client_ip << ": disconnected" << std::endl;

            break;

        }

        if (bytesReceived > 0) 
        {

            std::cout << thread_id << " - " << client_ip << ": " << std::string(buf, 0, bytesReceived) << std::endl;

            //send(clientSocket, buf, bytesReceived + 1, 0);

        }

    }

    std::cout << thread_id << " - " << client_ip << ": closing client socket & exiting thread..." << std::endl;

    closesocket(clientSocket);

}

void waitForConnections(SOCKET serverSocket) {

    sockaddr_in hint;

    hint.sin_family = AF_INET;
    hint.sin_port = htons(1337);
    hint.sin_addr.S_un.S_addr = INADDR_ANY;

    bind(serverSocket, (sockaddr*)&hint, sizeof(hint));
    listen(serverSocket, SOMAXCONN);

    while (true) {

        sockaddr_in client;

        int clientSize = sizeof(client);

        SOCKET clientSocket = accept(serverSocket, (sockaddr*)&client, &clientSize);

        if (clientSocket != INVALID_SOCKET) 
        {

            char host[NI_MAXHOST];      // Client's remote name

            ZeroMemory(host, NI_MAXHOST); // same as memset(host, 0, NI_MAXHOST);

            std::string client_ip = inet_ntop(AF_INET, &client.sin_addr, host, NI_MAXHOST);
            std::thread t(clientSocketHandler, clientSocket, client_ip);

            t.join();

        }

        Sleep(100);

    }

}

int main()
{
    // Initialze winsock
    WSADATA wsData;
    WORD ver = MAKEWORD(2, 2);

    int wsOk = WSAStartup(ver, &wsData);

    if (wsOk != 0)
    {
        std::cerr << "Can't Initialize winsock! Quitting..." << std::endl;

        return 1;
    }

    // Create a socket
    SOCKET serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    if (serverSocket == INVALID_SOCKET)
    {
        WSACleanup();
        std::cerr << "Can't create a socket! Quitting..." << std::endl;

        return 1;
    }

    // If serverSocketMode = 0, blocking is enabled; 
    // If serverSocketMode != 0, non-blocking mode is enabled.
    u_long serverSocketMode = 1;

    if (ioctlsocket(serverSocket, FIONBIO, &serverSocketMode) != NO_ERROR) 
    {
        WSACleanup();
        std::cerr << "Can't set socket to non-blocking mode! Quitting..." << std::endl;

        return 1;
    }

    // Disables the Nagle algorithm for send coalescing.
    // This socket option is included for backward 
    // compatibility with Windows Sockets 1.1
    BOOL flag = TRUE;

    if (setsockopt(serverSocket, IPPROTO_TCP, TCP_NODELAY, (const char *)&flag, sizeof(flag)) != NO_ERROR)
    {
        WSACleanup();
        std::cerr << "Can't set socket NO_DELAY option! Quitting..." << std::endl;

        return 1;
    }

    // Start listening for connections
    waitForConnections(serverSocket);

    // Cleanup winsock
    WSACleanup();

    system("pause");

    return 0;

}

Answer 1

這應該工作。 我刪除了無意義的事情，例如將套接字設置為非阻塞並禁用Nagle算法。 后者應該僅用於需要低毫秒交互性的事物。

但是，應該解決您的問題的重大變化是將join更改為detach 。 使用join會導致程序在繼續之前等待線程完成。 使用detach說“這個線程將在后台運行，我不關心以后學習它的命運。”

如果你不使用其中一個，並且::std::thread對象被銷毀，那么系統會拋出一個異常，因為你正在破壞你獲取有關一個線程是否退出的唯一方法。某種錯誤，說你不關心這些信息，或明確要求它。

我沒有Windows，所以我無法測試它：

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

#pragma comment (lib, "ws2_32.lib")

void clientSocketHandler(SOCKET clientSocket, std::string client_ip)
{
   char buf[4096];

   std::thread::id thread_id = std::this_thread::get_id();
   std::cout << thread_id << " - " << client_ip << ": connected" << std::endl;

   while (true)
   {

      ZeroMemory(buf, 4096);

      int bytesReceived = recv(clientSocket, buf, 4096, 0);

      if (bytesReceived == 0)
      {

         std::cout << thread_id << " - " << client_ip << ": disconnected" << std::endl;

         break;

      }

      if (bytesReceived > 0)
      {

         std::cout << thread_id << " - " << client_ip << ": " << std::string(buf, 0, bytesReceived) << std::endl;

         //send(clientSocket, buf, bytesReceived + 1, 0);

      }

   }

   std::cout << thread_id << " - " << client_ip << ": closing client socket & exiting thread..." << std::endl;

   closesocket(clientSocket);

}

void waitForConnections(SOCKET serverSocket)
{

   sockaddr_in hint;

   hint.sin_family = AF_INET;
   hint.sin_port = htons(1337);
   hint.sin_addr.S_un.S_addr = INADDR_ANY;

   bind(serverSocket, (sockaddr*)&hint, sizeof(hint));
   listen(serverSocket, SOMAXCONN);

   while (true) {

      sockaddr_in client;

      int clientSize = sizeof(client);

      SOCKET clientSocket = accept(serverSocket, (sockaddr*)&client, &clientSize);

      if (clientSocket != INVALID_SOCKET)
      {

         char host[NI_MAXHOST];      // Client's remote name

         ZeroMemory(host, NI_MAXHOST); // same as memset(host, 0, NI_MAXHOST);

         std::string client_ip = inet_ntop(AF_INET, &client.sin_addr, host, NI_MAXHOST);
         std::thread t(clientSocketHandler, clientSocket, client_ip);

         t.detach();

      }

      Sleep(100);

   }

}

int main()
{
    // Initialze winsock
    WSADATA wsData;
    WORD ver = MAKEWORD(2, 2);

    int wsOk = WSAStartup(ver, &wsData);

    if (wsOk != 0)
    {
        std::cerr << "Can't Initialize winsock! Quitting..." << std::endl;

        return 1;
    }

    // Create a socket
    SOCKET serverSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    if (serverSocket == INVALID_SOCKET)
    {
        WSACleanup();
        std::cerr << "Can't create a socket! Quitting..." << std::endl;

        return 1;
    }

    // Start listening for connections
    waitForConnections(serverSocket);

    // Cleanup winsock
    WSACleanup();

    system("pause");

    return 0;

}