I'm running the same code on 3 machines, but it lags on 2 machines. How would I trouble shoot this problem? Sorry if this is the wrong area to ask :(
Thanks

Please provide more information for us. We don't want to play "20 questions".

are you able to hold a small group on a stationary computer? Even a slow moving one can be tricky to hit at first, you need to lead the target a bit and try to get a line on the wider side. Perhaps a laser sight will help?

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Sorry, I had to, between your name and the title.
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Lag is difficult to diagnose. it could be in the hardware, the router/switch. It could be the machine decided to defrag or take a nap (suspend mode) or something. It could be something in your code. Could be fighting other network traffic, or too much data.
May want to start with wireshark -- it can tell you about the ecosystem traffic.
then if that does not help, try 2 machines, without anything in between but a cable.
that eliminates the router/switch.
you can also just do a dumb file transfer via the OS or something between them, eliminates your code as the source.

@Jonnin, You're hilarious! Once I get my hands on the computers I'll start troubleshooting it. Thanks for the tips.

Also look at Task Manager to see what else is running and what cpu/io other images are using.