python socket server monitor multi clients activity

Question

There is a socket server and multi clients, and every client will send a message to server in a fixed period. As a server how to listen every client do or not have sended the message in that period?

I think the server can record the every client connection time locally, and start a thread to periodically check the time interval between last time record and now. if more than the period client send message, it should be a timeout.

It seems a little complex and need a local file to record, is there a more convenient way to do that?

Answer 1

Ignoring the multi threaded part for now, because that is independent of main question: Keeping track of timing between messages of each client.

A simple map will do the job. Keep a dictionary of {socket: last time}, where last_time refers to the time whenever the last message from this specific socket was received.

• Whenever a new client comes, make a new entry in map and set the last_time based on whatever fits you best (-1 or 0 or current system time).
• Whenever a client sends the message, you check the time elapsed with that entry in map, and if it is in within required logic, update the map and do the extra stuff.
• If the received message is not within bounds, remove that entry from map, close the connection with client, do whatever you want.

For the corner case: if a client doesn't send any message, you need a separate logic that will run at regular intervals and checks if elapsed time for an entry is more than expected. If it is more, you know you need to delete it, close the connection, do whatever you want.

I don't think there is any other way to handle this issue. The best you can do is: write a class that handles this logic internally and exposes you to relevant abstractions:

• Did client sent the message within time?
• Add a client.
• Remove the client.
• Remove all clients which didn't send any message in last x seconds/minutes/hours.
• Close the connection with specific client.

Coming to multi threading part, you need to take care of concurrency issues in python (or in any language in general), because two or more threads can update the map simultaneously. Regarding python, if I remember correctly, it only allows you to run one thread at a time because of interpreter lock, so you can ignore this issue.

There are many ways to handle connections in sockets: multi threading, multi processing, using select/poll system calls, etc. They have their merits if used at appropriate place, but which one to use, is upto the OP.