如何使用winsock2与c ++实现多个并行连接？

Question

我正在尝试在VSC中使用c ++和winsock2实现一个简单的服务器，该服务器可以同时接受多个客户端并与之通信。我尝试使用多线程和一组客户端，看来我可以连接到多个客户端，但一次只能与一个客户端通信。一旦我关闭连接，下一个客户端就会连接。我相信这与线程的连接功能有关。但是我找不到其他解决方法。

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <thread>

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

#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"
#define MAXIMUM_CONNECTIONS 10

int connectionsCount = 0;
SOCKET clients[MAXIMUM_CONNECTIONS];

using namespace std;

void communicatingWithClient(SOCKET*);
void listenForConnection(SOCKET*);

int main()
{

    WSADATA wsaData;
    int iResult;

    SOCKET ListenSocket = INVALID_SOCKET;

    struct addrinfo *result = NULL;
    struct addrinfo hints;

    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0)
    {
        printf("WSAStartup failed with error: %d\n", iResult);
        WSACleanup();
        return 1;
    }
    printf("WSA started\n");
    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_PASSIVE;

    // Resolve the local address and port to be used by the server
    iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
    if (iResult != 0)
    {
        printf("getaddrinfo failed: %d\n", iResult);
        freeaddrinfo(result);
        WSACleanup();
        return 1;
    }

    // Create a SOCKET for the server to listen for client connections
    ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
    if (ListenSocket == INVALID_SOCKET)
    {
        printf("Error at socket(): %d\n", WSAGetLastError());
        freeaddrinfo(result);
        WSACleanup();
        return 1;
    }

    printf("ListenSocket created\n");
    // Setup the TCP listening socket
    iResult = bind(ListenSocket, result->ai_addr, (int)result->ai_addrlen);
    if (iResult == SOCKET_ERROR)
    {
        printf("bind failed with error: %d\n", WSAGetLastError());
        freeaddrinfo(result);
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    freeaddrinfo(result);

    thread listenThread(listenForConnection, &ListenSocket);

    listenThread.join();

    closesocket(ListenSocket);
    WSACleanup();
    return 0;
}

void listenForConnection(SOCKET *ListenSocket)
{
    int iResult;
    // Listen on the ServerSocket forever
    while(true)
    {
        printf("While Loop for listening started...\n");
        iResult = listen( *ListenSocket, SOMAXCONN);
        if (iResult == SOCKET_ERROR )
        {
            printf( "Listen failed with error: %d\n", WSAGetLastError() );
            closesocket(*ListenSocket);
            WSACleanup();
            return;
        }
        printf("Accepting client socket..\n");
        // Accept a client socket
        if (connectionsCount < 10) 
        {
            clients[connectionsCount] = accept(*ListenSocket, NULL, NULL);
            if (clients[connectionsCount] == INVALID_SOCKET)
            {
                printf("accept failed: %d\n", WSAGetLastError());
                closesocket(*ListenSocket);
                closesocket(clients[connectionsCount]);
                WSACleanup();
                return;
            }
            printf("Client accepted\n");
        }
        else
        {
            continue;
        }
        // Receive until the peer shuts down the connection
        thread communicationThread(communicatingWithClient, &clients[connectionsCount++]);
        communicationThread.join();
    }
}

void communicatingWithClient(SOCKET *ClientSocket)
{
    int iResult;
    int iSendResult;
    char recvbuf[DEFAULT_BUFLEN];
    int recvbuflen = DEFAULT_BUFLEN;

    do
        {
            printf("Receiving bytes from client...\n");
            iResult = recv(*ClientSocket, recvbuf, recvbuflen, 0);
            if (iResult > 0)
            {
                printf("Bytes received: %d\n", iResult);

                // Echo the buffer back to the sender
                iSendResult = send(*ClientSocket, recvbuf, iResult, 0);
                if (iSendResult == SOCKET_ERROR)
                {
                    printf("send failed: %d\n", WSAGetLastError());
                    closesocket(*ClientSocket);
                    WSACleanup();
                    return;
                }
                printf("Bytes sent: %d\n", iSendResult);
            }
            else if (iResult == 0)
            {
                printf("Connection closing...\n");
            }
            else
            {
                printf("recv failed: %d\n", WSAGetLastError());
                closesocket(*ClientSocket);
                WSACleanup();
                return;
            }
        }
        while (iResult > 0);

        // shutdown the send half of the connection since no more data will be sent
        iResult = shutdown(*ClientSocket, SD_SEND);
        printf("ClientSocket shut down\n");
        if (iResult == SOCKET_ERROR)
        {
            printf("shutdown failed: %d\n", WSAGetLastError());
            closesocket(*ClientSocket);
            WSACleanup();
            return;
        }
        closesocket(*ClientSocket);
}

Answer 1

您的问题是由此部分引起的：

// Receive until the peer shuts down the connection
thread communicationThread(communicatingWithClient, &clients[connectionsCount++]);  
communicationThread.join();  

更确切地说，通过此调用communicationThread.join（）;如果等到与客户的交流结束，您将无法与其他人交流。 （因为您必须等待通信线程完成才能创建新线程）。

您编写的代码因此为顺序

] >>

multithreaind的用途是允许线程在parallel中运行。如果您立即与每个创建同步，则将无法使用多线程，并且您的代码可能会被sequential

一个替换