Question

我正在创建一个客户端程序，它通过LAN与连接到我PC的设备进行通信。

我的程序和设备之间的典型通信如下：

Program -> Device   1616000D  08 02 00 00 00 21 11 A1 00 01 22 08 00 // Sender sends data (a specific command to the device) to Receiver
Program <- Device   16160002  80 00 // Receiver sends ACK to sender
Program <- Device   16160005  08 20 00 00 00 // Receiver sends command response to sender
Program -> Device   16160002  80 00 // Sender sends ACK to receiver

第一个字节序列的最后一个十六进制数表示要遵循的数据大小（D = 13个字节）。

我的发送程序如下：

bool TcpConnection::SendCommand(const Command& rCommand, const std::vector<BYTE>& rvecCommandOptions)
{
    std::vector<BYTE> vecCommandData;
    m_commandBuilder.BuildCommand(rCommand, rvecCommandOptions, vecCommandData);

    if (vecCommandData.empty())
        return false;

    PerIoData *pPerIoData = new PerIoData;
    if (!pPerIoData)
        return false;

    SecureZeroMemory(&(pPerIoData->m_overlapped), sizeof(WSAOVERLAPPED));

    pPerIoData->m_socket = m_socket.Get();
    pPerIoData->m_overlapped.hEvent = WSACreateEvent();
    pPerIoData->m_vecBuffer.assign(vecCommandData.begin(), vecCommandData.end());
    pPerIoData->m_wsaBuf.buf = (CHAR*)(&(pPerIoData->m_vecBuffer[0]));
    pPerIoData->m_wsaBuf.len = pPerIoData->m_vecBuffer.size();
    pPerIoData->m_dwFlags = 0;
    pPerIoData->m_dwNumberOfBytesSent = 0;
    pPerIoData->m_dwNumberOfBytesToSend = pPerIoData->m_wsaBuf.len;
    pPerIoData->m_operationType = OP_TYPE_SEND;

    if (!m_socket.Send(pPerIoData))
        return false;

    return true;
}

我的工作线程例程如下：

DWORD WINAPI TcpConnection::WorkerThread(LPVOID lpParameter)
{
    HANDLE hCompletionPort = (HANDLE)lpParameter;
    DWORD dwNumberOfBytesTransferred;
    ULONG ulCompletionKey;
    PerIoData *pPerIoData;

    DWORD dwNumberOfBytesReceived;
    DWORD dwNumberOfBytesSent;
    DWORD dwFlags;

    while (GetQueuedCompletionStatus(hCompletionPort, &dwNumberOfBytesTransferred, &ulCompletionKey, (LPOVERLAPPED*)&pPerIoData, INFINITE)) 
    {
        if (!pPerIoData)
            continue;

        if ((dwNumberOfBytesTransferred == 0) && ((pPerIoData->m_operationType  == OP_TYPE_SEND) || (pPerIoData->m_operationType  == OP_TYPE_RECEIVE)))
        {
            closesocket(pPerIoData->m_socket);
            delete pPerIoData;
            continue;
        }

        if (pPerIoData->m_operationType == OP_TYPE_SEND)
        {
            pPerIoData->m_dwNumberOfBytesSent += dwNumberOfBytesTransferred;
            if (pPerIoData->m_dwNumberOfBytesSent < pPerIoData->m_dwNumberOfBytesToSend)
            {
                pPerIoData->m_wsaBuf.buf = (CHAR*)(&(pPerIoData->m_vecBuffer[pPerIoData->m_dwNumberOfBytesSent]));
                pPerIoData->m_wsaBuf.len = (pPerIoData->m_dwNumberOfBytesToSend - pPerIoData->m_dwNumberOfBytesSent);

                if (WSASend(pPerIoData->m_socket, &(pPerIoData->m_wsaBuf), 1, &dwNumberOfBytesTransferred, 0, &(pPerIoData->m_overlapped), NULL) == 0)
                    continue;

                if (WSAGetLastError() == WSA_IO_PENDING)
                    continue;
            }
            else if (pPerIoData->m_dwNumberOfBytesSent == pPerIoData->m_dwNumberOfBytesToSend)
            {
                delete pPerIoData;
            }

            // Q1. Do I create a new instance of PerIoData here before calling WSARecv() or reuse pPerIoData?

            // QA. If I did do "PerIoData pPerIoData = new PerIoData" here, how do I handle if this momory allocation request has failed?  Should I simply "continue" or "return -1"?

            // QB. Or is this a wrong place to do this memory allocation to achive the typical communication between my program and the device?

            SecureZeroMemory(&(pPerIoData->m_overlapped), sizeof(WSAOVERLAPPED));

            pPerIoData->m_overlapped.hEvent = WSACreateEvent();
            pPerIoData->m_wsaBuf.buf = (CHAR*)(&(pPerIoData->m_vecBuffer[0]));
            pPerIoData->m_wsaBuf.len = pPerIoData->m_vecBuffer.size();
            pPerIoData->m_operationType = OP_TYPE_RECEIVE;

            if (WSARecv(pPerIoData->m_socket, &(pPerIoData->m_wsaBuf), 1, &dwNumberOfBytesReceived, &(pPerIoData->m_dwFlags), &(pPerIoData->m_overlapped), NULL) == 0)
                continue;

            if (WSAGetLastError() == WSA_IO_PENDING)
                continue;
        }
        else if (pPerIoData->m_operationType == OP_TYPE_RECEIVE)
        {
            if ((pPerIoData->m_vecBuffer[0] == 0x16) && (pPerIoData->m_vecBuffer[1] == 0x16))
            {
                // Q2. Do I need to do SecureZeroMemory(&(pPerIoData->m_overlapped), sizeof(WSAOVERLAPPED)); here?

                // Q3. Or do I new PerIoData?

                pPerIoData->m_wsaBuf.buf = (CHAR*)(&(pPerIoData->m_vecBuffer[0]));
                pPerIoData->m_wsaBuf.len = pPerIoData->m_vecBuffer.size();
                pPerIoData->m_operationType = OP_TYPE_RECEIVE;

                // QC. At this point two syn bytes (0x16) are received.  I now need to receive two more bytes of data (000D = 13 bytes) to find out the size of the actual command response data.
                // If I clear my m_vecBuffer here and try to resize its size to two, I get this debug assertion: "vector iterators incompatible" at runtime.  Do you know how I can fix this problem?

                if (WSARecv(pPerIoData->m_socket, &(pPerIoData->m_wsaBuf), 1, &dwNumberOfBytesReceived, &(pPerIoData->m_dwFlags), &(pPerIoData->m_overlapped), NULL) == 0)
                    continue;

                if (WSAGetLastError() == WSA_IO_PENDING)
                    continue;
            }

            // QD. I'm not sure how to structure this if clause for when m_operationType is OP_TYPE_RECEIVE.  I mean how do I distinguish one receive operation for getting two syn bytes from another for getting data size?
            // One way I can think of doing is to create more receive operation types such as OP_TYPE_RECEIVE_DATA_SIZE or OP_TYPE_RECEIVE_DATA?  So you can have something like below.
            // Is this how you would do it?
        }
        //else if (pPerIoData->m_operationType == OP_TYPE_RECEIVE_DATA_SIZE)
        //{
            // Call WSARecv() again to get command response data
        //}
    }

    return 0;
}

请在上面的代码中查看我的问题。

非常感谢

Answer 1

正如PerIoData类型所指的名称，每个不完整的I / O请求需要一个数据结构。从您使用PerIoData或WSASend启动异步I / O时，WSARecv结构应该保持不变，直到您使用{从I / O完成端口检索该请求的完成数据包的时间为止{1}}。
当您即将开始新请求时，您应始终重新初始化GetQueuedCompletionStatus结构。
只要I / O请求完成，您就可以重用OVERLAPPED结构。鉴于您已从I / O完成端口检索PerIoData，您可以将其重新用于后续请求。只需确保您已重置该结构中的任何适用字段，以使其处于适合新I / O请求的状态。

编辑回答后续问题：

一个。我会pPerIoData，因为即使您无法发起其他请求，也希望继续处理I / O事件。如果您没有continue，那么您将无法再处理I / O完成。在你continue之前，你可能想要调用某种错误处理程序。

B中。我认为没有必要分配“正确”或“错误”的地方，但请记住，当你在那里分配continue时，你实际上最终做的是重复分配和删除相同的数据循环中反复结构。当我使用I / O完成端口编写代码时，我会预先分配一个PerIoData等效的池并重新使用它们。

℃。我没有足够的背景知道答案。显示执行此操作的代码以及断言命中的行，我可能会提供帮助。

d。您可以按照建议将操作类型分解为更细粒度的组件，例如PerIoData操作。作为警告，在每个OP_TYPE_RECEIVE_DATA_SIZE呼叫上读取几个字节将无法满足您的需求。 Winsock电话很贵;要求几个字节需要很多开销。我建议您在一个WSARecv中的PerIoData缓冲区中读取更大的数据块。然后从该缓冲区中提取您的大小调整信息，然后开始从该缓冲区中复制数据。如果到达的数据超出了缓冲区的数量，那么您可以进行额外的WSARecv调用，直到您阅读完其余内容。

如何为IOCP构造工作线程逻辑

1 个答案: