Max Retransmission Reached

1

I’ve successfully set up an MQTT server which I can connect to and which relays messages across my mesh, but on the sending device messages are marked “Max Retransmission Reached”, incorrectly indicating that the messages are never picked up by any other nodes.

All settings appear to be correct, including the MQTT uplink and downlink toggles for the relevant channel on each device.

Is there something I’m missing? Does anyone know how I can avoid the confusing failure message?

2

Which firmware version are you using? There was a fix for this in version 2.2.17.

3

Each of my devices are on 2.2.16.

I’ll update them now :+1:t2:

4

Hi, I’m observing similar behavior on 2.2.17 (both T-Echo units). I’ve confirmed that messages are being delivered via MQTT.

5

Hi @Stan, did upgrading to 2.2.17 make a difference for you?

6

It’s hard to say because MQTT sporadically works for me :open_mouth:

7

Please try a different channel than the default LongFast. There’s just too much traffic there and your device gets overloaded.

1 Like
8

I could try LongSlow, but do many people use the other settings?

9

We’ve maxed our node list and haven’t had any overload issues on LongFast, but there’s a first for everything. If everything is working and firmware is up to date, but still getting a max transmission error (but receiving node still receives the message) it usually means something is blocking signal. For instance, the first receiving node may have a bad or poorly tuned antenna, and isn’t able to broadcast back an ACK.

EDIT: Sorry, I should probably read slower now that I see LongFast being on MQTT, and could indeed cause traffic issues.

10

I’ve disabled MQTT — now running mesh radio only — and am still seeing max RT errors, despite the message at least sometimes being delivered. The SNR is low and I suspect the acks aren’t getting to the sending node, as you propose.

11

Not every message gets an ack, it still may have been delivered

12

Hi @garth, thanks for replying. Since you mentioned that not every message gets an ack, is observing max RT reached messages typical behavior? I read through Without ACK/NACK, message is lost? - #32 by einstein2218 but it’s a bit beyond my understanding.

13

Sharing this in case it helps anyone else wondering:

Since ACKs for broadcasts would rapidly flood the channel, the normal ACK behavior is suppressed. Instead, the original sender listens to see if at least one node is rebroadcasting this packet (because naive flooding algorithm).
Mesh Broadcast Algorithm | Meshtastic