c++ - 读取 QTcpSocket

Question

我有一个与 UNIX C++ 套接字的套接字连接，连接后，我有一个逐字节读取的循环，直到我获得完整的消息。我知道我将要接收的消息的前两个字节及其长度(15 个字节)。所以函数看起来像:

bool mastControl::findPacket(int sockfd, st_messageMastToPc * messageReceived, bool * connected) {

    int n = 0;
    bool messageFound = false;
    char * buffer = (char *) messageReceived;

    unsigned int pos = 0;

    while ( ((n = read(sockfd, &(buffer[pos]), 1)) > 0) and not messageFound) {

         if (n == 1) {
            pos++;

            if ( (pos == 1) && (buffer[0] == 0x02)) { // First byte to receive
                std::cout << "INFO - Rcv1" << std::endl;
            } else if ( (pos == 2) && (buffer[1] == 0x33) ) { // Second byte
                std::cout << "INFO - Rcv2" << std::endl;
            } else if (pos >= uiMessageMastToPcSize) { // Full msg received
                messageFound = true;
                std::cout << "INFO - Complete message received" << std::endl;
            } else if (pos <= 2) { // Wrong values for the first 2 bytes
                std::cout << "WARN - Reseting (byte " << pos << " -> " << int(pos) << ")" << std::endl;
                pos = 0;
            }
        }
    }

    if (n < 0){
        //EROR
        *connected = false;
    }

    return messageFound;
}

现在我正在使用 QTcpSockets 实现相同的功能。建立连接，然后我调用:

if(socket->waitForReadyRead(Global::tiempoMaximoDeEsperaParaRecibirDatosMastil)){
                /* Read socket to find a valid packet */
                if (findPacket(socket, &messageReceived)) {
                    qDebug()<<"New packet found!";
//...
}
}

所以我等到有一些信息准备好供您读取，然后调用 findPacket，现在几乎相同，逐字节读取:

bool mastControl::findPacket(QTcpSocket *socket, st_messageMastToPc * messageReceived) {
    int n = 0;
    bool messageFound = false;
    char * buffer = (char *) messageReceived;
    unsigned int pos = 0;

    while ( ((n = socket->read(&(buffer[pos]), 1)) >= 0) and not messageFound) {
        if (n == 1) {
            qDebug()<<"Recibido: "<<buffer[pos]<<", en pos: "<<pos;
            pos++;
            if ( (pos == 1) && (buffer[0] == 0x022)) {
                qDebug()<<"0x02 in first position";
//                std::cout << "INFO - Rcv1" << std::endl;
            } else if ( (pos == 2) && (buffer[1] == 0x33) ) {
                qDebug()<<"0x33 in second";
                std::cout << "INFO - Rcv2" << std::endl;
            } else if (pos >= uiMessageMastToPcSize) {
                messageFound = true;
                std::cout << "INFO - Complete message received" << std::endl;
            } else if (pos <= 2) {
                std::cout << "WARN - Reseting (byte " << pos << " -> " << int(pos) << ")" << std::endl;
                pos = 0;
            }
        }
    }

    if (n < 0){
      qDebug()<< "Disconnected. Reason: " << socket->errorString();
    }

    return messageFound;
}

看起来很像，但行不通。在等待 waitForReadyRead 后，我进入 findPacket 的循环并且我能够读取接收到的前 4 个字节。之后，不再接收到数据。它仍然在 findPacket 的循环中一次又一次地检查，但是读取函数总是返回 0 字节读取。没有收到新信息。这是不可能的，因为服务器每隔几毫秒发送一次相同的数据包，所以即使我丢失了一些数据，最终我也应该读到一些东西。

那么，我做错了什么？我应该以不同的方式等待吗？我应该再次等待第一次读取函数返回 0 字节读取吗？这个读取函数和 C++ 库函数有什么区别？

Answer 1

最后，问题在于尝试一直读取，而不是在读取函数返回第一个零之后等待新数据。这样做就像一个魅力!