QTcpServer listen successfully,but without emiting newConnection

[pinkie]

Hi , I test QTcpServer of Qt5.3.1. The steps are following:

m_pTCPServer = new QTcpServer(this);
m_pTCPServer->setMaxPendingConnections(1);
QObject::connect(m_pTCPServer,SIGNAL(newConnection()),this,SLOT(server_New_Connect()));
if(m_pTCPServer->listen(QHostAddress::Any, m_localPort))
{
setCommStatus(CommunicationStatus::Connected);
ret = true;
}

I can test the listening is OK with a tcp client connection, but the slot 'server_New_Connect' never be emitted.

Anyone has already encounted this problem,pls give me some advice,thanks a lot.

[VRonin]

@pinkie said in QTcpServer listen successfully,but without emiting newConnection:

QObject::connect(m_pTCPServer,SIGNAL(newConnection()),this,SLOT(server_New_Connect()));

Can you check the return value of connect? the easiest way is to wrap it into Q_ASSUME: Q_ASSUME(QObject::connect(m_pTCPServer,SIGNAL(newConnection()),this,SLOT(server_New_Connect())));

[mchinand]

@pinkie said in QTcpServer listen successfully,but without emiting newConnection:

I can test the listening is OK with a tcp client connection

By this, do you mean that your client does a connectToHost() and a connected() signal is subsequently emitted by the client?

Have you looked a the Fortune client/server examples?

[Pablo J. Rogina]

@pinkie I lack context of where you're creating your QTcpServer object but the following code is working fine for me (Qt 5.9.0): basic Qt Widgets Application project with m_pTCPServer member added to MainWindow class :

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QtNetwork/QTcpServer>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

public slots:
    void server_New_Connect();

private:
    Ui::MainWindow *ui;
    QTcpServer* m_pTCPServer;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    m_pTCPServer = new QTcpServer(this);
    m_pTCPServer->setMaxPendingConnections(1);
    QObject::connect(m_pTCPServer, SIGNAL(newConnection()), this, SLOT(server_New_Connect()));

    if (m_pTCPServer->listen(QHostAddress::Any, 9999))
    {
        qDebug() << "Server up and listening!";
    }
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::server_New_Connect()
{
    qDebug() << "New connection!";
}

program output when using command telnet localhost 9999

Server up and listening!
New connection!

[pinkie]

Thanks all for your help. I find the point. The new QTcpServer... code is within run function of my thread. It works well if I move it outside. I should learn more about QTcpServer and QThread. Thank you.

[Taz742]

@pinkie
Mark this post a solved.

[Pablo J. Rogina]

@pinkie you may want to take a look at threaded fortune server example. And as @Taz742 mentioned, please don't forget to mark the post as solved.

[Taz742]

What happend when connection server&client is always open?