I have never used iptables before, read the documentation and decided to make a restriction on connecting devices from different IP addresses to port 10000. For example, the limit = 1 means that the second device will not be able to connect.

I tried this command: sudo iptables -A INPUT -p 6 --syn --dport 10000 -m connlimit --connlimit-above 1 -j DROP
But still the second device connected without any problems:
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