A ticket, a stub, and a queue that moves
Selling at the door means printing at the door. A ticket with a code that scans, a numbered stub at the cloakroom, and a receipt if someone asks for one. Nobody wants to run to a computer in the office for any of that.
Try it
Say what you have at the door, sell a few tickets, and watch the paper come out where it should.
Nothing selected yet
What went over the wire
One call per printer. This is the whole integration.
Sell something and it shows up here.
Three tickets, one call
A group of four buys at once. That is not four calls — it is one call with copies: 4, and four tickets come out with the counter running on. The queue at the door is the reason: every extra round trip is a second somebody stands still, and at opening time those seconds are what you feel.
What you need
A receipt printer at the door
Any ESC/POS printer. A ticket is a strip of paper with a code on it, so the same box that prints receipts prints tickets.
One bridge
Two USB printers per bridge. Box office and cloakroom next to each other is one bridge.
Whatever you sell with
A ticketing system, a spreadsheet, a form. If it can make an HTTP request, it can print.
Questions from the door
What if a printer is off?
The sale is not lost. The job waits in the queue and comes out the moment that printer reports back, and the answer says which one printed and which one did not.
Does the code on the ticket scan?
It is a real barcode or QR, drawn at the printer's own resolution. What you scan back is exactly what you sent.
The cloakroom is in another room. Same network?
Not necessarily. Each bridge makes its own outgoing connection, so a printer on the guest wifi works too.
What if someone presses sell twice?
Send the sale number as an idempotency key and the second press returns the first answer. No second ticket.
On your own printer
Make an account, plug a bridge into a printer you already have, and the same call prints on paper.