TCP Winsock：接受多个连接/客户端答案

【问题标题】：TCP Winsock: accept multiple connections/clientsTCP Winsock：接受多个连接/客户端
【发布时间】：2013-02-17 14:04:06
【问题描述】：

我试图增加客户端，并将其发送给每个客户端。但它只适用于一个，在一个客户端连接服务器后，它对传入的连接毫无用处。

while(true)
{
    if(Sub = accept(Socket, (sockaddr*)&IncomingAddress, &AddressLen))
    {
        for(int i = 0; i < MaxUsers; i++)
        {
            if(!ClientAddress[i].sin_family)
            {
                ClientAddress[i] = IncomingAddress;
                char Version[128], Dir[256], Path[256], URL[128], Message[256];
                GetCurrentDirectory(256, Dir);
                sprintf(Path, "%s\\Version.ini", Dir);
                GetPrivateProfileString("Default", "Version", "1.0.0.0", Version, 128, Path);
                GetPrivateProfileString("Default", "URL", "", URL, 128, Path);
                GetPrivateProfileString("Default", "Message", "", Message, 256, Path);
                send(Sub, Version, 128, 0);
                send(Sub, Message, 256, 0);
                break;
            }
        }
        continue;

    }
}

【问题讨论】：

标签： c++ sockets winapi tcp winsock2

【解决方案1】：

当然不能接受新客户端，因为服务器只处理接受的客户端，即服务器正忙。

解决方案很简单：为每个接受的客户端创建一个新线程并在那里处理客户端会话。只需使用_beginthreadex() (#include <process.h>)：

unsigned __stdcall ClientSession(void *data)
{
    SOCKET client_socket = (SOCKET)data;
    // Process the client.
}

int _tmain(int argc, _TCHAR* argv[])
{
    ...

    SOCKET client_socket;
    while ((client_socket = accept(server_socket, NULL, NULL))) {
        // Create a new thread for the accepted client (also pass the accepted client socket).
        unsigned threadID;
        HANDLE hThread = (HANDLE)_beginthreadex(NULL, 0, &ClientSession, (void*)client_socket, 0, &threadID);
    }
}

顺便说一下，send()/recv() 函数不保证所有数据会在一次调用中发送/接收。有关这些函数的返回值，请参阅文档。

【讨论】：

【解决方案2】：

接受套接字后，为客户端请求创建单独的线程。然后继续等待新的接受。

例如：

    ...
    while (1)
    {
        AcceptSocket = SOCKET_ERROR;

        while (AcceptSocket == SOCKET_ERROR )
        {
            AcceptSocket = accept( m_socket, NULL, NULL );
        }

        printf( "Client Connected.\n");

        DWORD dwThreadId;
        CreateThread (NULL, 0, ProcessClient, (LPVOID) AcceptSocket, 0, &dwThreadId);
    }
    ...

ProcessClient函数可能是这样的：

DWORD WINAPI ProcessClient (LPVOID lpParameter)
{
    SOCKET AcceptSocket = (SOCKET) lpParameter;

    // Send and receive data.
    int bytesSent;
    int bytesRecv = SOCKET_ERROR;
    char sendbuf[2000]="";
    char recvbuf[2000]="";

    char timebuf[128];

    sprintf(sendbuf, "Hello, it's a test server at %s:%d (commands: 1, 2, exit)\n", ipaddr, port);
    bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);

    if (bytesSent == SOCKET_ERROR)
    {
        printf( "Error at send hello: %ld\n", WSAGetLastError());
        goto fin;
    }

    while (1)
    {
        _strtime( timebuf );
        ZeroMemory (recvbuf, sizeof(recvbuf));

        bytesRecv = recv( AcceptSocket, recvbuf, 32, 0);
        printf( "%s Client said: %s\n", timebuf, recvbuf);

        if (strcmp(recvbuf, "1") == 0)
        {
            sprintf(sendbuf, "You typed ONE\n");
            //printf("Sent '%s'\n", sendbuf);
            bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);

            if (bytesSent == SOCKET_ERROR)
            {
                printf( "Error at send: %ld\n", WSAGetLastError());
                goto fin;
            }
        }
        else if (strcmp(recvbuf, "2") == 0)
        {
            sprintf(sendbuf, "You typed TWO\n");
            //printf("Sent '%s'\n", sendbuf);
            bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);

            if (bytesSent == SOCKET_ERROR)
            {
                printf( "Error at send: %ld\n", WSAGetLastError());
                goto fin;
            }
        }
        else if (strcmp(recvbuf, "exit") == 0)
        {
            printf( "Client has logged out\n", WSAGetLastError());
            goto fin;
        }
        else
        {
            sprintf(sendbuf, "unknown command\n");
            //printf("Sent '%s'\n", sendbuf);
            bytesSent = send( AcceptSocket, sendbuf, strlen(sendbuf), 0);

            if (bytesSent == SOCKET_ERROR)
            {
                printf( "Error at send: %ld\n", WSAGetLastError());
                goto fin;
            }
        }
    }

fin:
    printf("Client processed\n");

    closesocket(AcceptSocket);
    return 0;
}

【讨论】：