It’s been a while since we discussed this topic (2 yrs), so re-starting here.
Background: Different SIM’s have different timeouts for UDP device listening sockets. For example, the Particle SIM has an extraordinarily long timeout of 23 minutes. My Hologram SIM, currently used on my Particle Electron, times out much faster, within a minute or two, it seems (some SIM’s can be as little as 30 seconds). This means I need to use a “keep alive” ping on the Electron to keep the connection open, allowing me to use such features as OTA. Pings cost data, which cost money (122 bytes per keep-alive ping). A 2-minute ping frequency translates to 2.6 MB/month.
I would like to know what the OFFICIAL keep-alive time is for Hologram SIM’s, for the various operators, or at least for the ones I use (AT&T, T-Mobile, Verizon).
Are the values expected to be the same for 3G and Cat-M?
UPDATE: Looks like my Particle Electron / Hologram SIM combo on AT&T goes deaf after about a minute. Wow. That will cost me a ton of data to keep UDP up and open; something like 5.2MB / month, not including any data payload. Let’s call it 6MB for the pricing model, so 6 x 0.6, or $3.60, plus the basic $0.40. Looks like $4.00 / month per device, which is now more expensive than a Particle SIM. How about that!