Before doing that, please consider contributing to an existing project first. There are many out there and they'd love more contributors.

I cannot agree with this enough. So many resources wasted trying to replicate what's already been done, but this is not an issue with XMPP only.

There are still lots of fun challenges in many clients and servers if that is what you're looking for.

Which is the best XMPP server?

For the server mentioned here...

OpenFire = written in Java

Prosody = Lua

Ejabberd = Erlang

Prosody is small and works for most people. Ejabberd is what powers production servers of bigger operators, it's also used in MMORPGs.

I can't say which is best, I can only say I use Prosody and am very happy with it.

Here's a howto on setting it up: https://homebrewserver.club/configuring-a-modern-xmpp-server...

I love Prosody. It took five minutes to set up and it's been flawlessly running ever since. We use it for internal company talk, pasting code, sending files. If you don't need 1M+ clients it's great.

I also set up an ejabberd instance for a client years ago when Prosody was not a thing but it's more complicated to set up. They changed the config file from Erlang to YAML a while ago but it's still complex. But it's nice it has a web interface to create users and easier to not get bothered about it once it's up and running. Ejabberd can handle a massive number of clients.

Here's an older discussion about XMPP self hosting:

https://news.ycombinator.com/item?id=8783794

Not sure if it's the best, but I tried openfire, worked great for my use case, it was easy to deploy on k8s.

Is there something you're looking for specifically? Just asking, because xmpp is currently my thing, and some of the interesting bits and tricks sometimes are a bit hidden, but there is lot's of stuff possible that I didn't think would be.

What XMPP stuff are you currently working on?

Triaging bugs in ChatSecure without regular access to an iDevice.

I am mostly on the admin/user side of things.