Use Raspberry Pi to explore mDNS

Intro
I am confounded by the Bonjour field on my d-Link DCS-931L IP webcam. I should be able to use it to see my desired hostname, but it doesn’t take. Why?

The details
Having a Raspberry Pi on the same network I realized I could at least learn definitively whether or not my new name was being taken, or what the old name was.

You install avahi-discover to do that:

$ sudo apt-get install avahi-discover

Those who follow my blog will realize I am big on Linux command-line, not so much on GUIs. I mention it because unfortunately avahi-discover only works in the GUI. Not having a console I actually had to fire up vncserver and use my vncviewer on my PC! Then I could launch avahi-discover from a terminal window running on the GUI.

The extra fuss was just a few steps anyway, and well worth it.

avahi-discover broke down my home network and all the discovered devices in a very orderly fashion, e.g., the webcam appeared under web servers.

And what did I learn? Indeed, my name had not “taken” for some reason. So the system-supplied name was there instead. For the record that is

dcs931le1a6.local

And testing it:

$ ping dcs931le1a6.local

did indeed show me that it was resolvable by that name form my local network. My PC could reach it by that name as well. I tied to name it DCS-931L-BALL, and I know someone else who did this successfully, and I had even done it in the past, but it was just not taking it this time.

References and related
mDNS is multicast DNS. It’s designed for home networks. It’s pretty common from wjhat I see, yet largely unknown since It people do not encounter it in enterprise environments. As usual Wikipedia has a good article on it.
Superimposing crosshairs on a webcam image.