Custom read handler for sockets demo for appserver.py and appclient.py (libserver, libclient)

ℹ️
https://github.com/realpython/materials/blob/master/python-sockets-tutorial/app-server.py
https://github.com/realpython/materials/blob/master/python-sockets-tutorial/app-client.py
https://github.com/realpython/materials/blob/master/python-sockets-tutorial/libserver.py
https://github.com/realpython/materials/blob/master/python-sockets-tutorial/libclient.py

You can report issues and problems here, but we typically won't be able to provide 1:1 support outside the channels listed above.

Describe the bug
I am trying to use the appclient and appserver demo from the above sockets tutorial and want to process a custom function using the data read from the server read or client read.

To Reproduce
NA

Expected behavior
Able to run a custom function after a read is done in server or client using the data read.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• Device: [e.g. iPhone6] NA
• OS: [e.g. iOS8.1] Linux, Windows
• Browser [e.g. stock browser, safari] NA
• Version [e.g. 22] NA

Additional context
NA

Read app-server.py and app-client.py alongside libserver.py and libclient.py to understand how socket data is currently read. Define and document the intended custom read-handler behavior for both server and client, with completion demonstrated by processing the data after a read.