Linux Netcat 在 Raspberry Pi 上按预期工作但不是 QTCPSocket答案

【问题标题】：Linux Netcat works as Expected but not QTCPSocket on Raspberry PiLinux Netcat 在 Raspberry Pi 上按预期工作但不是 QTCPSocket
【发布时间】：2015-02-11 14:40:14
【问题描述】：

我有 2 个 Raspberry Pi，一个发送器和一个接收器，它使用 USB WiFi 加密狗充当接入点。我在发送方上有 Qt 5.4.0 代码，它使用 USB/FTDI XBee SB6 WiFi 单元在作为客户端成功连接到它的接入点后向接收方 Pi 发送 TCP 数据包。

代码通过 XBee 正确地将 TCP 数据包发送到接收器 Pi，因为我可以在接收器上使用 Netcat 程序并观察数据包成功到达端口 0x2616 (9750)：

>> sudo nc -l 10.10.10.1 9750
>> HELLOHELLOHELLO

当我尝试使用 QTCPSocket 将接收器 Pi 上的 Netcat 替换为以下 Qt 代码时，它永远不会在套接字上接收任何数据。我的意思是永远不会调用“readyRead()”插槽。我以 sudo 运行它，发送者 Pi 正在执行与 Netcat 捕获输出时完全相同的传输。到底是怎么回事？我是否将 QTCPSocket 连接到本地端口错误？我怎样才能让它工作？谢谢！

#include "tcpreceiver.h"

// Debug
#include <QDebug>
#define API_DEBUG true
#include <QApplication>

TcpReceiver::TcpReceiver(QObject *parent) :
    QObject(parent)
{

    // Debug
    qDebug() << "Setting up a TCP Socket...";

    // Create a socket
    m_Socket = new QTcpSocket(this);

    // Bind to the 2616 port
    m_Socket->connectToHost("10.10.10.1", 0x2616);
    //m_Socket->connectToHost( QHostAddress::Any, 0x2616 );

    qDebug() << "Socket is valid: " << m_Socket->isValid();
    //qDebug() << "Socket value: " << m_Socket->

    // Get notified that data is incoming to the socket
    connect(m_Socket, SIGNAL(readyRead()), this, SLOT(readyRead()));

    // Init to Zero
    m_NumberTCPPacketsReceived = 0;

}

void TcpReceiver::readyRead() {

    qDebug() << "Received data...";

    // When data comes in
    QByteArray buffer;
    buffer.resize(m_Socket->bytesAvailable());

    // Cap buffer size
    int lenToRead = buffer.size();
    if ( buffer.size() > NOMINAL_AUDIO_BUFFER_SIZE ) {
        lenToRead = NOMINAL_AUDIO_BUFFER_SIZE;
    }

    // Read the data from the TCP Port
    m_Socket->read(buffer.data(), lenToRead);

...

    // Count up
    m_NumberTCPPacketsReceived++;

}

【问题讨论】：

没有 sudo 是否 nc 工作？你用 sudo 运行你的 Qt 程序吗？

标签： linux qt tcp qt5 qtcpsocket

【解决方案1】：

这是你的做法：

#include "tcpreceiver.h"

// Debug
#include <QDebug>
#include <QHostAddress>

TcpReceiver::TcpReceiver(QObject *parent) :
    QObject(parent)
{

    // Create a server
    qDebug() << "Creating a TCP Server...";

    // Create the server
    m_Server = new QTcpServer(this);

    // Listen on the proper port
    m_Server->listen( QHostAddress::Any, 0x2616 );

    // Hook up signal and slots
    connect(m_Server, SIGNAL(newConnection()), this, SLOT(gotNewConnection()));
    connect(m_Server, SIGNAL(acceptError(QAbstractSocket::SocketError)), this, SLOT(error()));

}

void TcpReceiver::gotNewConnection() {

    qDebug() << "Got a new TCP Connection";

    // Get the socket
    m_Socket = m_Server->nextPendingConnection();
    if(m_Socket->state() == QTcpSocket::ConnectedState)
    {
        qDebug() << "Socket was connected at: " << m_Socket->peerAddress();
    }

    // Hook up some signals / slots
    connect(m_Socket, SIGNAL(disconnected()),this, SLOT(disconnected()));
    connect(m_Socket, SIGNAL(readyRead()),this, SLOT(readyRead()));

}

void TcpReceiver::disconnected() {

    qDebug() << "Socket Disconnected...";

    // Cleanup
    m_Socket->deleteLater();

}

void TcpReceiver::error() {

    qDebug() << "Error: " << m_Server->errorString();

}

void TcpReceiver::readyRead() {

    qDebug() << "Received data...";

    // Now read data
    QByteArray buffer;
    if (m_Socket->canReadLine()) {

        buffer = m_Socket->readLine();
        qDebug() << "Got Data: " << buffer;
    }

}

【讨论】：