UDP packets cannot be sent to or received from the server. #6

New Issue

amras · 2026-04-29T08:19:53Z

amras commented

2026-04-29 08:19:53 +00:00

The first time connecting to a new instance of mumble, the mumble client displays the message "UDP packets cannot be sent to or received from the server. Switching to TCP mode."

(in the client: Settings > Network > Force TCP mode should be off)

This probably shouldn't be happening, since we have a UDP entrypoint.

The first time connecting to a new instance of mumble, the mumble client displays the message "UDP packets cannot be sent to or received from the server. Switching to TCP mode." (in the client: Settings > Network > Force TCP mode should be _off_) This probably shouldn't be happening, since we have a UDP entrypoint.

amras commented

2026-05-08 15:49:36 +00:00

This was causing some additional issues with clients being unable to connect over UDP (needing to force TCP mode). So we investigated this a bit further.

Identified Issue

Issue is on traefik's end - the app container drops outbound UDP packets.

That's by design. By default, traefik terminates UDP connections after 3s of idleness. In our multinode setup, that's not enough. Those 3s of idleness can occur during startup or at random during network hiccups. And once it happens, all UDP connections are broken.

https://doc.traefik.io/traefik/reference/install-configuration/entrypoints/#opt-udp-timeout

Proposed Solution

The simplest option seems to be to increase the timeout.

traefik.yml.tmpl needs to be modified:

  mumble-udp:
    address: ":64738/udp"
    udp:
      timeout: 10

I'll test this for a while in chaos mode before I make a pull request.

This was causing some additional issues with clients being unable to connect over UDP (needing to force TCP mode). So we investigated this a bit further. ## Identified Issue Issue is on traefik's end - the `app` container drops outbound UDP packets. That's by design. By default, traefik terminates UDP connections after 3s of idleness. In our multinode setup, that's not enough. Those 3s of idleness can occur during startup or at random during network hiccups. And once it happens, all UDP connections are broken. https://doc.traefik.io/traefik/reference/install-configuration/entrypoints/#opt-udp-timeout ## Proposed Solution The simplest option seems to be to increase the timeout. `traefik.yml.tmpl` needs to be modified: ```yaml mumble-udp: address: ":64738/udp" udp: timeout: 10 ``` I'll test this for a while in chaos mode before I make a pull request.

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Reference: coop-cloud/mumble#6