Find receipt printers on the network and read their status from Node.js

Discover printers

const { discoverNetworkPrinters } = require('retail-print-kit');

const printers = await discoverNetworkPrinters({ identify: true });
for (const p of printers) {
  console.log(p.host, p.identity?.maker, p.identity?.model, p.identity?.profile?.id);
}
// 192.168.1.50 EPSON TM-T88V epson-tm-t88

It sweeps every private /24 network the machine is on for hosts that accept connections on port 9100 (raw printing), about two seconds per network. With identify: true it asks each one what it is and suggests a profile. Options: port, timeout, concurrency, subnets.

From the command line:

npx retail-print-kit discover --identify

Identify one printer

const { identify } = require('retail-print-kit');
const { NetTransport } = require('retail-print-kit/net');

const t = new NetTransport('192.168.1.50');
await t.open();
const id = await identify(t);   // { maker, model, firmware, set, profile }
await t.close();

ESC/POS printers answer GS I with their maker, model and firmware. A printer that stays silent but answers a Star status request is reported as Star Line Mode.

For USB, the vendor id is enough to pick a starting profile before sending anything:

const { profileForUsb } = require('retail-print-kit');
profileForUsb(0x04b8).id;          // 'epson-tm-t88'
profileForUsb(0x0519, 0x0001).id;  // 'star-tsp100'

Read status: paper out, cover open, drawer

const printer = new Printer(new NetTransport('192.168.1.50'), profiles['epson-tm-t88']);
await printer.open();
const s = await printer.status();
await printer.close();

if (!s.online) console.log('printer is offline');
if (s.coverOpen) console.log('cover is open');
if (s.paperOut) console.log('out of paper');
if (s.paperNearEnd) console.log('paper is running low');
if (s.cutterError) console.log('cutter jam');

Status uses the ESC/POS real-time commands DLE EOT 1..4, and ESC ACK SOH on Star Line Mode. It works over the network, USB and serial. Check status before a long print job rather than after: a printer with its cover open accepts the bytes and prints nothing.

npx retail-print-kit status --net 192.168.1.50

Related: print a receipt.

Install

npm install retail-print-kit

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