NielsLeenheer

console.hex = (d) => console.log((Object(d).buffer instanceof ArrayBuffer ? new Uint8Array(d.buffer) : 
typeof d === 'string' ? (new TextEncoder('utf-8')).encode(d) : 
new Uint8ClampedArray(d)).reduce((p, c, i, a) => p + (i % 16 === 0 ? i.toString(16).padStart(6, 0) + '  ' : ' ') + 
c.toString(16).padStart(2, 0) + (i === a.length - 1 || i % 16 === 15 ? 
' '.repeat((15 - i % 16) * 3) + Array.from(a).splice(i - i % 16, 16).reduce((r, v) => 
r + (v > 31 && v < 127 || v > 159 ? String.fromCharCode(v) : '.'), '  ') + '\n' : ''), ''));

NielsLeenheer

I have a web app that needs to talk to point of sale hardware: receipt printers, customer displays, 
cash drawers and payment terminals. Direct communication from the web app with these devices is 
impossible, so I created a native app that can be installed on the computer that can talk to the 
devices. The app runs a web server that exposes these devices using a REST api.

The native app registers itself upon startup with a webservice. It sends its own IP address on 
the local network and the server also sees the external IP address of the network. The web app 
sends a discovery request to the webservice and it receives all the local IP addresses which 
have the same external IP address.