Unusual send failures

I started a Thingy:91 in the morning. It reports some data every hour over CoAP/DTLS 1.2 CID. What irritates me is, that it shows quite a lot of send failures. Sure, that maybe cause by UDP, but using a lot more devices with other CoAP/DTLS 1.2 CID endpoint, I’m usually get only a very few failures.

if possible, you may check my device id `655bafe778b93cd14474d10a.
It reports 10 messages and 6 failures.
Before sending data to golioth, that device uses an other endpoint for 4 days, sending about 110 messages with only 1 failure. The SIM card is the same. Do you have some server-side logs for that device?

Let me add.
the 6 failures happens before 1:07:02 PM. After that, no additional failures occur.

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@achim.kraus thank you for reporting this! We’ll look into these send failures.

Just to mention:
If you don’t see something in the server side logs, don’t waste time.
I will then enable the client side logs and we will see, if it happens again.

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It seems, there are two points:

First, the DTLS session seems to get lost every couple of days. I think, “DTLS graceful restart” isn’t implemented/supported.

Seconds, my Thingy app frequently “calls the watchdog”, but that doesn’t happen on my other Thingies, which are connected to Californium. I guess, there is a very bad and nasty bug in my code, when the device tries to reconnect. The good point, it’s pretty reproducible every couple of days.

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First, the DTLS session seems to get lost every couple of days. I think, “DTLS graceful restart” isn’t implemented/supported.

@achim.kraus this is correct and something we are actively working on addressing, especially given our recent support for CIDs. I will keep you updated on our progress!

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