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Comment by Closi | Hacker News Reader

I doubt the second bit is true - they will still be marking the ticket as used in their backend.

They are just trying to prevent scalpers printing off tickets 10 times and selling them outside the venues as a scam, which happened at every large concert I have ever been to until recently (so I assume this is working!).

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You would hope... But they often run the scanners in offline mode (e.g. at temporary / seasonal events) so there can be lag in the backends being updated.

Heard from a friend who got straight into two events in the same city recently - they presumed the show was at one outdoor venue but the scanners let them straight in at the first (wrong) venue. Went to the correct venue and got in there without any issue too (this suggests one or both venues were offline or using offline scanners).

Hm. So I guess at a small venue that has 3 door people with offline scanners, you have a 2/3 chance of success if you're the second of two people sharing a barcode. Combined with the obvious 3/3 success being the first person, that averages out to 5/6 chance if both of you (oblivious to each other) schedule your arrival similarly.

My experience from visiting many many of them is that 80-90% of small venues don’t even bother with scanners.

not really offline but someone who works in industry here once detailed out that each scanner has it's own copy of a SQLite database that is being updated as fast as possible based on inserts of other scanners since any downtime is a big deal at these venues

i.e., theoretically duplicate tickets would be identified but not instantly but still pretty quickly

> they will still be marking the ticket as used in their backend.

I assume that's true, but it makes me wonder how their scanners are connected to the server.

I mean, if 10,000 people showing up to an event with smartphones overwhelms wireless networks, wont that also kick their scanners off the network?

They'd probably like to have a system where, if a scanner loses its connection, it can still validate tickets. It could store a copy of validated tickets locally, and upload it when the network connection is restored - that would mean a copied ticket would have to make sure they go to a different door/scanner. But it would allow copying.

I have no idea what connectivity options are available in current scanners, but it sounds like a viable solution could be to use an RF band that customers don't overwhelm, similar to wireless microphones perhaps, with a little hub situated nearby that consolidates the list of already-scanned tickets, possibly standalone or possibly on a wired network that includes other far-away entrances.

Was going to say it shouldn't be hard to run a wire around an entire stadium, but maybe some popup outdoor venues that might be complicated. Could use line of sight towers for fun.

Simplest answer is a private wifi network for the scanners.

It's also the best answer.

It's all off-the-shelf electronics and standard protocols. Venue provides some wifi with a "Ticketbastard" SSID (or whatever) at entry points, and the COTS-built barcode-validating devices use that. Easy-peasy.

They might also provide other wireless networks for other purposes (definitely for vendors [$$$], but perhaps also for regular house staff, touring staff, and maybe even the guests who pay for it all!), but they'll all be under the venue's control and coordination: Other than the odd personal hotspot that wanders in, there's not necessarily any meaningful outside interference on 2.4/5GHz wifi bands in a big venue.

It's pretty easy to make short-range wifi work reliably in that kind of RF environment, such as the chokepoints where tickets are validated. (Modern apartment dwellers will have worse interference problems than that.)

There’s actually a ton of interference in the 2.4 GHz space, especially at venues like outdoor festivals. However your solution does work. I work at a festival that provides a WiFi network and an Ethernet drop for the ticket scanners. We have to use multiple APs to cover the main entrance area, but it’s feasible.

I was thinking more along the lines of a stadium crowd than an outdoor festival, but yes: I agree. I've had miserable luck with 2.4GHz stuff in festival environments where people camp out for a few days. :)

I don't pay very much attention to the ticket-scanning devices while I'm getting into a big show (which is generally a rather unpleasant experience on my side), but:

Don't they allow usage of 5GHz bands? Unlike 2.4GHz, I've had tremendous success with 5GHz bands in all kinds of environments -- including outdoor festivals.

900mhz networks like halow or even lorawan should do

Even at huge venues i dont expect requests would be over 5 rps

5 RPS, per scanner, surely?

No way, scanning tickets is slow because it rarely works seamlessly. It's pretty standard to stand there for a few seconds moving your phone back and forth and/or rotating it. Or when one person has all the tickets for their party and has to scroll to the next one between scans.

I think maybe 4-15 seconds between scans per scanner, at best.

Can you imagine 5 people moving thru scanner in 1 second?

Even at 1 rps that's if we assume 1 meter distance that's 3.6 km/h or a normal walking pace. Do you ever see crowd at ticketing move at walking pace?

Not at all, I was imagining over speccing the system.

E.g. this weekend I went to a show at a 70,000 seat arena. Knowing from experience, there are 4 entrances. This time there were 10 people scanning tickets at the gates I entered. Friends reported the same at the one they came in.

5 RPS per scanner is obviously overkill, but if those 10 at one gate were linked to a hub that could issue 5 RPS I would call that adequate, if barely.

If all 4 gate areas were linked centrally to a system that could do 5 RPS, well, actually, that might explain the throughput I experienced getting through lol

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