客户端-服务器回声聊天（多路复用 I/O + 线程）

Question

我刚开始学习 C 语言，我正在尝试处理 Windows 套接字。

问题是服务器只能接受和发送消息一次。我使用了调试模式，发现工作在服务器部分的 select() 中停止了。它在客户端似乎很好（但我不确定）并且在我的代码中没有看到问题。但是我有这样的结果。怎么了？

我注意到我的 tv.tv_sec 没有定义，我在 select 之前定义了它，没有任何改变。

而且可以肯定的是：因为我需要接收和发送消息，所以我不需要在 accept() 中写入描述符，对吗？

客户端在我尝试发送消息时使用了 CreateThread 函数。发送在main()

中的while(1)循环

服务器部分：

int main(int argc, char* argv[])
{
    /* definitions, WSAStartup(), socket(), bind(), listen() 
    Listening socket is a returned value of listen() function*/

        FD_ZERO(&readSet);
        FD_ZERO(&writeSet);

        while (1)
        {
            // SELECT (LISTENING SOCKET)
            FD_ZERO(&readSet);
            FD_SET(listeningSocket, &readSet);
            tv.tv_sec = 5;
            printf("Listening: Read FD: %d; Write FD : %d;\n", FD_ISSET(listeningSocket, &readSet), FD_ISSET(listeningSocket, &writeSet));
            if ((retVal = select(listeningSocket + 1, &readSet, NULL, NULL, 0)) == SOCKET_ERROR)
            {
                printf("Select error ");
                break;
            }
            else if (retVal == 0)
            {
                printf(". . .\n");
                continue;
            }
            else
            {
                // READ SD
                if ((FD_ISSET(listeningSocket, &readSet)) != SOCKET_ERROR)
                {
                    if ((newSocketDescriptor = accept(listeningSocket, (struct sockaddr *)&clientAddr, &clientAddrSize)) == SOCKET_ERROR)
                    {
                        printf("Accept error ");
                        break;
                    }
                    FD_ZERO(&readSet);
                    FD_SET(newSocketDescriptor, &readSet);

                    HOSTENT *hst = gethostbyaddr((const char *)&serverAddr.sin_addr.s_addr, 4, AF_INET);
                    printf("Welcome %s (%s:%d) new connected\n", hst->h_name, inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));
                    printf("Read FD: %d; Write FD : %d;\n", FD_ISSET(newSocketDescriptor, &readSet), FD_ISSET(newSocketDescriptor, &writeSet));

                    // READ
                    if (FD_ISSET(newSocketDescriptor, &readSet) != 0)
                    {
                        if ((numBytes = recv(newSocketDescriptor, &bufferData[0], sizeof(bufferData), 0)) == SOCKET_ERROR)
                        {
                            printf("Recv failed \n");
                            freeSocketInformation(newSocketDescriptor);
                            break;
                        }

                        bufferData[numBytes] = '[=11=]';
                        printf("Client -> Server: %s\n", &bufferData[0]);
                    }

                    // WRITE
                    FD_ZERO(&writeSet);
                    FD_SET(newSocketDescriptor, &writeSet);

                    printf("Read FD: %d; Write FD : %d;\n", FD_ISSET(newSocketDescriptor, &readSet), FD_ISSET(newSocketDescriptor, &writeSet));
                    if (FD_ISSET(newSocketDescriptor, &writeSet) != 0)
                    {
                        //fgets(&bufferData[0], sizeof(bufferData), stdin);
                        if (send(newSocketDescriptor, &bufferData[0], strlen(&bufferData[0]), 0) == SOCKET_ERROR)
                        {
                            printf("Send error ");
                            freeSocketInformation(newSocketDescriptor);
                            break;
                        }
                        bufferData[numBytes] = '[=11=]';
                        printf("Server -> Client: %s\n", &bufferData[0]);

                    }
                    printf("Read FD: %d; Write FD : %d;\n", FD_ISSET(newSocketDescriptor, &readSet), FD_ISSET(newSocketDescriptor, &writeSet));

                    FD_SET(newSocketDescriptor, &readSet);
                }
            }
        }
        //FD_CLR(listeningSocket, &readSet);
        closesocket(newSocketDescriptor);
    } while (FALSE);
    printf("- Error code: %d\n", WSAGetLastError());
    closesocket(listeningSocket);
    WSACleanup();
    return 0;
}

客户端部分（使用代码末尾的CreateThread函数）：

/* definitions, socket(), connect()*/
        if (ioctlsocket(socketDescriptor, FIONBIO, (unsigned long *)&nb) != 0)
        {
            printf("ioctlsocket error ");
            break;
        }


            FD_ZERO(&writeSet);
            FD_SET(socketDescriptor, &writeSet);
            if ((retVal = select(socketDescriptor + 1, NULL, &writeSet, NULL, &tv)) == SOCKET_ERROR)
            {
                printf("Send non-blocking error ");
                break;
            }
            else if (retVal == 0)
            {
                printf("Non-blocking connect time limit is expired");
                break;
            }
        }
        printf("Connection with %s\n", SERVERADDR);

        DWORD thID;
        printf("Socket Desciptor: %d\n", socketDescriptor);
        HANDLE hThread = CreateThread(NULL, NULL, HandleReadThread, (LPVOID)socketDescriptor, NULL, &thID);
        printf("Thread ID: %d\n", thID);

        while (1)
        {
            // WRITE
            printf("Client -> Server: ");
            fgets(&bufferData[0], sizeof(bufferData), stdin);

            FD_ZERO(&writeSet);
            FD_SET(socketDescriptor, &writeSet);
            tv.tv_sec = 5;
            if ((retVal = select(socketDescriptor + 1, NULL, &writeSet, NULL, &tv)) == SOCKET_ERROR)
            {
                printf("Send non-blocking error ");
                break;
            }
            if (FD_ISSET(socketDescriptor, &writeSet) != 0)
            {
                if (send(socketDescriptor, bufferData, strlen(&bufferData[0]), 0) == SOCKET_ERROR)
                {
                    printf("Send error ");
                    break;
                }
            }
        }
    } while (FALSE);
    printf("- Error code: %d\n", WSAGetLastError());
    closesocket(socketDescriptor);
    WSACleanup();
    return 0;
}

DWORD WINAPI HandleReadThread(LPVOID serverSocket)
{
    SOCKET socketDescriptor;
    socketDescriptor = (SOCKET)serverSocket;
    char bufferData[MAXDATASIZE] = { 0 };
    int retVal;
    fd_set readSet;
    timeval tv = { 0 };
    tv.tv_sec = 5;

    int numBytes;
    int nclients = 0;

    while (1)
    {
        FD_ZERO(&readSet);
        FD_SET(socketDescriptor, &readSet);

        if ((retVal = select(socketDescriptor + 1, &readSet, NULL, NULL, &tv)) == SOCKET_ERROR)
        {
            printf("Select error. Error code: %d", WSAGetLastError());
            break;
        }
        else if (retVal == 0)
        {
            //printf(". . .\n");
            continue;
        }

        else
        {
            //FD_ZERO(socketDescriptor, &readSet);
            //FD_SET(socketDescriptor, &readSet);
            // READ
            if (FD_ISSET(socketDescriptor, &readSet) != 0)
            {
                if ((numBytes = recv(socketDescriptor, &bufferData[0], sizeof(bufferData), 0)) == SOCKET_ERROR)
                {
                    printf("Recv error in Thread. Error code: %d\n", WSAGetLastError());
                    break;
                }
                printf("\nSocket Desciptor: %d\n", socketDescriptor);
                bufferData[numBytes] = '[=12=]';
                printf("Server -> Client: %s\n", &bufferData[0]);
            }
        }
    }
    closesocket(socketDescriptor);
    return 0;
}

Answer 1

嗯，我自己解决了。条件

if ((FD_ISSET(listeningSocket, &readSet)) != 0)

while(1) 循环一直有效，它应该在 accept() 函数之后完成。我还在 FD_SET 之后的 while(1) 开头添加了这些行 for readSet:

if (newSocketDescriptor)
{
    FD_SET(newSocketDescriptor, &readSet);
}

聊天开始了，但还有很多事情要处理:)

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