Sockets of multi connect server's client do not close on minor change from eco server to normal server and normal client

ℹ️
After I use it (https://github.com/realpython/materials/blob/master/python-sockets-tutorial/multiconn-client.py) with a small change (minor change from echo server to normal server) -

- after sending and receiving messages from the client and server, the client does not close; or
- all data.messages have been exausted, the client does not close.

https://stackoverflow.com/questions/70640602/sockets-in-python-client-not-closing-after-event-read-write-events-in-multi-conn

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Describe the bug
After minor change from echo server to normal server:

- after sending and receiving messages from the client and server, the client does not close; or
- all data.messages have been exausted, the client does not close.

To Reproduce
Provided in the stackoverflow question

Expected behavior
The client should close. Looks like it does not get into the if not recv_data code while I was checking. The program should reach the code. No major changes to the code has been made other than sending data from messages section. :

if not recv_data:
    print("closing connection", data.connid)
    sel.unregister(sock)
    sock.close()

Screenshots
Added to link:
https://stackoverflow.com/questions/70640602/sockets-in-python-client-not-closing-after-event-read-write-events-in-multi-conn

Desktop (please complete the following information):

• OS: [e.g. iOS] Win, Linux

Additional context
NA

Bắt đầu với python-sockets-tutorial/multiconn-client.py và bản tái hiện Stack Overflow được liên kết; so sánh thay đổi của echo-server với luồng normal-server được mô tả. Xác nhận rằng sau khi các thông báo đã được xử lý hết, client đi đến nhánh if not recv_data được hiển thị và đóng lại. Hoàn thành có nghĩa là client đóng một cách đáng tin cậy trong cả hai trường hợp được mô tả.