Proxy Error During Client Connection

Hello guys, when i configure my server first time everything was working well. But today I opened and tried connection and got this error. Anyone who has idea?

Hi, i suggest you to remove localhost from listen.
gameServer.listen(PORT);

or:

import dns from 'dns';
import os from 'os';

dns.lookup(os.hostname(), (error, address, fam) => {
gameServer.listen(PORT, address || 'localhost');
console.log(Running on ws://${address}:${PORT});
});