Support Zeroconf incl. Avahi and Bonjour

(Note that this issue hast been updated in the title and in the description to align it to the current state of tech. The issue was originally posted in 2013). See the records in the History for details

What is the benefit? Why is this valuable?

As a user, I want to use Qt network API to be able to discover and broadcast services in an automated way. If there is no need for new API, I wish to get an example and documentation how to use Avahi services from a Qt application.

What are common use cases?

The main use case are IoT devices.

Technical information

A part of the zeroconf is Avahi which includes an implementation of mDNS (https://en.wikipedia.org/wiki/Multicast_DNS). Over the years, the functionality of Bonjour and Avahi is available on Windows, macOS, iOS and ships with most Linux and BSD distributions. At least mDNS is supported on Android in various forms since a while https://blog.esper.io/android-dessert-bites-26-mdns-local-47912385/

According https://en.wikipedia.org/wiki/Avahi_(software), Bonjour from Apple is a different implementation even though having the same origins. There might be differences impacting Qt as a cross-platform framework

Avahi itself is a framework with other addtional functionality https://www.avahi.org. There a reference on https://inqlude.org/libraries/avahi-qt.html mentioning Qt binding in the Ahavi itself which seems to provide an adapter for Qt applications

On KDE, Ahavi is supported in https://api.kde.org/frameworks/kio/html/index.html

A bit older but a good overview in German is under https://www.linux-magazin.de/ausgaben/2006/03/null-arbeit/

Qt currently provides:

https://doc.qt.io/qt-6/qtnetwork-multicastreceiver-example.html
https://doc.qt.io/qt-6/qtnetwork-multicastsender-example.html

Community references:

• https://forum.qt.io/topic/7179/mdns-query/8
• the above is pointing to https://github.com/alex-spataru/qMDNS