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

阅读 app-server.py 和 app-client.py，以及 libserver.py 和 libclient.py，以了解当前如何读取 socket 数据。为 server 和 client 定义并记录自定义读取处理程序的预期行为，并通过在读取后处理数据来展示完成情况。