QTcpSocket, can't read incoming data

Question

I try to write simple server, using Qt and C++. Here is code:

   #include "mytcpserver.h"

MyTcpServer::MyTcpServer(QObject *parent) :
    QObject(parent)
{
    server = new QTcpServer(this);


    // whenever a user connects, it will emit signal
    connect(server, SIGNAL(newConnection()),
            this, SLOT(newConnection()));



    if(!server->listen(QHostAddress("127.0.0.1"), 3333))
    {
        qDebug() << "Server could not start";
    }
    else
    {
        qDebug() << "Server started!";
    }
}

   void MyTcpServer::on_readyRead()
  {
QTcpSocket * senderSocket = dynamic_cast<QTcpSocket *>(sender());
if (senderSocket)
{
    qDebug() << "reading data";
    qDebug() << senderSocket->readAll();
}
  }

  void MyTcpServer::newConnection()
{
    // need to grab the socket
QTcpSocket *sok=new QTcpSocket();
sok = server->nextPendingConnection();
if (sok)
{
    connect(sok,SIGNAL(readyRead()),this,SLOT(on_readyRead()));
    connect(sok,SIGNAL(disconnected()),sok,SLOT(deleteLater()));
}
sok->write("Writing");
}

And part of client on PHP:

$address = "127.0.0.1";
$service_port = "3333";
echo "Attempting to connect to '$address' on port '$service_port'...";
$result = socket_connect($socket, $address, $service_port);
if ($result === false) {
    echo "socket_connect() failed.\nReason: ($result) " . socket_strerror(socke$
} else {
    echo "OK.\n";
}

$in = "HEAD / HTTP";
$out = '';

echo "Sending HTTP HEAD request...";
socket_write($socket, $in, strlen($in));
echo "OK.\n";
echo "Reading response:\n\n";
while ($out = socket_read($socket, 2048)) {
    echo $out;
}

The problem is that I can't read from php client, specifically, signal readyRead isn't emitted. Also if i try to type in command line: telnet 127.0.0.1 3333 then server only responds "Writing" and exit.

Answer 1

Try this:

#include "mytcpserver.h"

MyTcpServer::MyTcpServer(QObject *parent) :
    QObject(parent)
{
    server = new QTcpServer(this);

    // whenever a user connects, it will emit signal
    connect(server, SIGNAL(newConnection()), this, SLOT(newConnection()));


    if(!server->listen(QHostAddress("127.0.0.1"), 3333))
    {
        qDebug() << "Server could not start";
    }
    else
    {
        qDebug() << "Server started!";
    }
}

void MyTcpServer::on_readyRead()
{ 
    QTcpSocket * senderSocket = dynamic_cast<QTcpSocket*>(sender());
    if(senderSocket)
    {
        qDebug() << "reading data";
        qDebug() << senderSocket->readAll();
    }
}

void MyTcpServer::newConnection()
{
    // need to grab the socket
    QTcpSocket * newSocket = server->nextPendingConnection();
    if(newSocket)
    {
        connect(newSocket ,SIGNAL(readyRead()),this,SLOT(on_readyRead()));

        //Additionnal auto clean-up without keeping track of the pointer
        connect(newSocket ,SIGNAL(disconnected()),newSocket ,SLOT(deleteLater()));
    }
}

(When you declare this:

QTcpSocket *sok=new QTcpSocket();

This creates a local QTcpSocket pointer, which hides the sok member of your class. Also, you create a QTcpSocket with new, and lose it at the next line (memory leak)

sok = server->nextPendingConnection();

So the sok member variable of your class is never used with an incoming connection.

You are using a member variable called sok in MyTcpServer class and a local variable sok in MyTcpServer::on_readyRead, this is a bad idea.

Proper use of QTcpServer would be:

• Store incoming connections in a member variable pointer
• Connect its readyRead signal