C++ WinSock2 等待客户端发送数据

Question

我有一个多线程套接字服务器，它应该与客户端进行连续对话，所以我将我的 recv 放在 while(true) 中以保持连接一直持续到其中一侧关闭它。我遇到的问题是，当客户端没有发送任何东西时，服务器一直在尝试接收数据，最终导致它崩溃，因为它什么也没有读取，所以我想知道是否有办法让 recv 停止，直到有实际数据要接收。

这是处理客户端连接的函数的代码:

void Communicator::clientHandler(SOCKET client)
{
    try
    {
        while (true)
        {
            char codeBuff[1];
            recv(client, codeBuff, 1, 0);
            int code = static_cast<int>(static_cast<unsigned char>(codeBuff[0]));
            char lengthBuff[4];
            recv(client, lengthBuff, 4, 0);
            int dataLength = lengthBuff[0] << 24 | lengthBuff[1] << 16 | lengthBuff[2] << 8 | lengthBuff[3];
            char* dataBuff = new char(dataLength);
            recv(client, dataBuff, dataLength, 0);
            dataBuff[dataLength - 1] = 0;

            std::vector<char> dataVec(dataBuff, dataBuff + dataLength);
            Request r = {
                code,
                std::time(nullptr),
                dataVec
            };

            std::copy(dataVec.begin(), dataVec.end(), std::ostream_iterator<char>(std::cout, "")); // For debug purposes, prints infintiely

            IRequestHandler* handler = nullptr;
            {
                std::lock_guard<std::mutex> locker(m_clientsMu);
                handler = m_clients.find(client)->second;
            }

            if (handler->isRequestRelevant(r))
            {
                RequestResult res = handler->handleRequest(r);
                {
                    std::lock_guard<std::mutex> locker(m_clientsMu);
                    delete[] m_clients.find(client)->second;
                    m_clients.find(client)->second = res.newHandler;
                }
                send(client, &res.response[0], res.response.size(), 0);
            }
            else
            {
                ErrorResponse res = { "Invalid request type" };
                std::vector<char> packet = JsonPacketSerializer::serializeResponse(res);
                send(client, &packet[0], packet.size(), 0);
            }
        }
    }
    catch (...)
    {
        closesocket(client);
        throw;
    }
}

我用来测试服务器的一些基本 python 代码:

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, socket.IPPROTO_TCP)
s.connect(('127.0.0.1', 8080))
s.send(bytes([101, 0, 0, 0, 40, 123, 34, 112, 97, 115, 115, 119, 111, 114, 100, 34, 58, 34, 49, 50, 51, 52, 53, 54, 34,
              44, 34, 117, 115, 101, 114, 110, 97, 109, 101, 34, 58, 34, 116, 101, 115, 116, 34, 125]))
msg = s.recv(1024)
print(msg)

Answer 1

char* dataBuff = new char(dataLength);

这将创建一个 char，最有可能的值是dataLength & 255，dataBuff 将指向那个一个 char。您分配一个 char 数组，如下所示:

char* dataBuff = new char[dataLength];

您还必须稍后释放内存:

delete[] dataBuff;

您还需要注意 recv 的返回值，即接收到的字节数(或 SOCKET_ERROR 指示错误)。