Multiclient TCP server

Bremenpl

Hello there,
I want to create a simple TCP server application that would handle multiple TCP clients. Normally I would create a separate thread for each connected client. In the past I have seen solutions concerning subclassing the QThread like this one.

But I feel like this is an obsolete and an overkill approach (I do not sublass QThread for a long time now). What would be the recommended modern Qt way of tackling this topic? Is using QTcpServer and QTcpClient even the way to go, or is it unnecessarily to low level approach?

I would appreciate all help.

J.Hilk

hi @Bremenpl

In the past I have seen solutions concerning subclassing the QThread like this one.

But I feel like this is an obsolete and an overkill approach

it is, mostly born out of a convoluted documentation

Take a look at the threaded fortune server example
https://doc.qt.io/qt-5/qtnetwork-threadedfortuneserver-example.html

should get you started

Bremenpl

@J-Hilk Thank you for answer. I have seen this example already- it is subclassing the QThread as well.

J.Hilk

@Bremenpl
you're right, I assumed it was updated 😡

Well, how you're actually supposed to do it, is now in the documentation,
See the detailed description of the QThread class
https://doc.qt.io/qt-5/qthread.html#details

The first section

Bremenpl

@J-Hilk Thank you for the link. In this case it is the way I am doing it for a while now. I thought maybe there are some new higher level approaches to this. Thank you for help!

Christian Ehrlicher

The only thing you have to take care when subclassing QThread is that the (possible) slots in your object derived from QThread are executed in the correct thread by moving the derived object into the thread. Otherwise there is no real difference.

kshegunov

Here, have a spin. Opinions are also appreciated.

VRonin

@Bremenpl said in Multiclient TCP server:

Normally I would create a separate thread for each connected client

This is a myth. Follow @kshegunov 's link

Bremenpl

@VRonin Thank you for answer.
I did mean a generic approach, in which the separate thread indeed is needed. Maybe in this design it will be unnecessary, but that's is also why I wanted to hear some opinions.

VRonin

1 client = 1 thread is actually unsustainable once the number of connected clients start increasing.
In the code linked to the chat example, both in the simple and advanced projects, you can easily see the clients are actually distributed among QThread::idealThreadCount() threads rather than having 1 per client.
It also only makes sense if there is some actual work to do in that secondary thread

Bremenpl

@VRonin said in Multiclient TCP server:

idealThreadCount

I see, I will check this topic out, sounds reasonable. Thank you.