QTcpSocket in a console app
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I'm somewhat new to Qt, having only had it for a week and devoting hours of self-learning/research to it. I'm trying to produce a console app that utilizes QTcpSocket and some general use Qt classes to try my hand at console app event handling. I started by attempting to produce a client program for an old peer-to-peer protocol called Hotline -- that is, an incomplete one that simply does a handshake and gets confirmation then disconnects, which shouldn't require multiple threads I think. It does this by writing 'TRTPHOTL' and the 16-bit values 1 and 2 to the socket. If successful, the server is to respond with 'TRTP' and two 16-bit values of 0, which I'd usually retrieve by reading the socket buffer. I come from C# but have prior knowledge in C++ as well.
What follows is my attempt at what I described above using C++ and Qt 4.8.2, and the .pro file as well for convenience. Following that I have posted the sample I had written and tested successfully in C#. Before suggesting I stick with C# though, I will say I prefer C++ because of its advantages over C#, but until finding out about Qt I hadn't used it due to lack of a suitable toolkit.
This doesn't seem to do as I intended. It compiles, but the output confuses me. On Win32 it has a chance to output the input as I code it to, but on Linux, nothing. The error below is given on both platforms:
@QObject::connect: Cannot connect (null)::destroyed() to QHostInfoLookupManager::waitForThreadPoolDone()@
hlclient.cpp:
@#include <QCoreApplication>
#include <QByteArray>
#include <QTcpSocket>
#include <QTextStream>int main()
{
QTcpSocket * sock = new QTcpSocket();
QTextStream out(stdout);
QByteArray hi("TRTPHOTL\x00\x01\x00\x02"); // TRTPHOTL (int16)1 (int16)2
sock->connectToHost("localhost", 5500);
if (sock->waitForConnected(10000))
{
sock->write(hi.data());
if (sock->waitForBytesWritten(10000))
{
out << "Wrote " << hi.data() << "\n";
hi.clear();
if (sock->waitForReadyRead(10000))
{
hi = sock->readAll();
out << "Read " << hi.data() << "\n";
}
}
sock->disconnectFromHost();
}
sock->close();
delete sock;
}
@hlclient.pro:
@TEMPLATE = app
TARGET =
DEPENDPATH += .
INCLUDEPATH += .
CONFIG += console
QT += network
SOURCES += hlclient.cpp@HLClient.cs:
@using System;
using System.Net;
using System.Net.Sockets;
using System.Text;static class HLClient
{
static void Main(string[] args)
{
TcpClient sock = new TcpClient("localhost", 5500);
byte[] data = {0x54, 0x52, 0x54, 0x50, 0x48, 0x4f, 0x54, 0x4c, 0x00, 0x01,
0x00, 0x02};
NetworkStream stream = sock.GetStream();
stream.Write(data, 0, data.Length);
Console.WriteLine("Sent stuff");
data = new byte[8];
string resp = string.Empty;
int bytes = stream.Read(data, 0, data.Length);
resp = Encoding.ASCII.GetString(data, 0, bytes);
Console.WriteLine("Received {0}", resp);
stream.Close();
sock.Close();
}
}@ -
First of all,
@
QByteArray hi("TRTPHOTL\x00\x01\x00\x02"); // TRTPHOTL (int16)1 (int16)2
@
is wrong. which equals
@
QByteArray hi("TRTPHOTL"); // TRTPHOTL (int16)1 (int16)2
@what you need is
@
QByteArray hi("TRTPHOTL\x00\x01\x00\x02", 12); // TRTPHOTL (int16)1 (int16)2
@Second, You need a QCoreApplication instance
so, change
@
int main()
{
@
to
@
int main(int argc, char** argv)
{
QCoreApplication app(argc, argv);
@ -
Alright did that. However my "return a.exec();" statement (declared QCoreApplication as 'a') now makes my app sit there and do nothing.
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Learn about asyncronic programming. Really. Instead of using the waitFor... methods, just use the signal/slot based ones and react to the incommig data. Don't try to spin your own eventloop or something like that, just use Qt's one.
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Please comment the last line // delete sock; and try again and see what you get.
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Alright, well I restructured my program and derived QTcpSocket as to implement signals. However, though I overrode connected(), disconnected(), and readyRead(), I am unsure how to connect them, as QCoreApplication's slots aren't really suitable.
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It will be more clear for beginners when they understand the basics of socket programming , plz follow the link .. http://csharp.net-informations.com/communications/csharp-socket-programming.htm it will provide the basics.
vayne.