Troubleshooting¶

Failure modes, in rough order of how often you'll hit them.

DAPPS won't start¶

"Refusing to start: callsign is N0CALL"¶

You haven't set DAPPS_CALLSIGN. Set it in the systemd unit / docker compose / shell environment:

DAPPS_CALLSIGN=M0LTE-1

The placeholder is a deliberate safety net - DAPPS won't transmit frames stamped with N0CALL because that would propagate garbage onto the air.

Exit code 78¶

Operationally-fatal config error: a port is already in use, or another configured resource isn't available. The journal (or stdout, if you're running interactively) will have the actual error one line above. Common causes:

MQTT port (1883) already in use by another broker on the same host. Either stop the other broker or set DAPPS_MQTT_PORT to a free port.
Dashboard port (5000) already in use - set ASPNETCORE_URLS=http://0.0.0.0:5001 (or whatever).
UDP listen port already in use - disable the UDP datagram bearer with DAPPS_UDP_LISTEN_PORT=0, or pick a different port.

The unit file's RestartPreventExitStatus=78 keeps systemd from hot-looping on a problem that won't fix itself; the journal message tells you what to fix.

Database errors on first start¶

DAPPS expects to be able to create a SQLite file at data/dapps.db (relative to the working directory) or wherever you've pointed it. If the working directory isn't writable, startup fails. On Linux/systemd the recommended unit uses WorkingDirectory=/var/lib/dapps; make sure that exists and is owned by the runtime user.

Packet-node connection problems¶

DAPPS connects to the packet node over either AGW (DAPPS_NODE_BEARER=agw, the default - works with BPQ, Direwolf, AGWPE, ...) or RHPv2 (DAPPS_NODE_BEARER=rhpv2, required for XRouter). The dashboard's Packet node card on the home page shows the bearer + host:port DAPPS is using and a reachability dot.

"Packet-node connection refused" / repeated reconnects¶

DAPPS can't reach the bearer port on DAPPS_NODE_HOST (DAPPS_AGW_PORT for AGW, DAPPS_RHP_PORT for RHPv2). Check:

The packet node is actually running and the bearer is enabled.
- BPQ AGW: AGWPORT=8000 in bpq32.cfg, no # commenting it out, BPQ restarted since.
- XRouter RHPv2: RHPPORT=9000 in XROUTER.CFG, XRouter restarted.
Network connectivity from where DAPPS runs to where the node runs. nc -vz <node-host> <port> from the DAPPS host should connect.
No firewall in the way.
For non-loopback XRouter, ACCESS.SYS allows your DAPPS host's subnet (flag 1 for callsign-only). Loopback is allowed without an entry.

"Packet-node connection drops repeatedly"¶

DAPPS reconnects automatically (with backoff). If it's flapping every few seconds:

Check the packet node's logs for whether it's actively closing the connection. Some BPQ misconfigurations cause AGW to disconnect clients on every L2 event.
Check for two DAPPS instances accidentally sharing a callsign - the second binding wins and the first one sees its inbound dispatch evaporate.

Inbound sessions never arrive (BPQ AGW)¶

A remote node can c <your-callsign> and lands at the BPQ node prompt, but not at the DAPPSv1> prompt. Check:

The APPLICATION 1,DAPPS,,,,, 0 line is in bpq32.cfg and BPQ has been restarted since adding it.
The CMD field on the APPLICATION line is empty (the ,,,,,). Older recipes had C N HOST K TRANS S here - for DAPPS, leave it empty so BPQ doesn't run a node command on inbound, just dispatches the L2 'C' frame to the registered AGW client.
DAPPS is registering the right callsign. The startup log shows AGW: registered <callsign> for inbound dispatch. If the callsign there doesn't match what the remote is connecting to, it won't route.
AGW exact-match is by call+SSID. M0LTE-1 is different from M0LTE-7.

Inbound sessions never arrive (XRouter RHPv2)¶

A remote node can c <your-callsign> and lands at the XRouter node prompt, but not at the DAPPSv1> prompt. Check:

DAPPS bound the callsign at startup. Look for RHP inbound: listener bound to <callsign> on handle <N> in the log.
The DAPPS callsign is not declared in any APPL block, NODECALL, CONSOLECALL, or CHATCALL in XROUTER.CFG. XRouter claims those callsigns for its own internal use; DAPPS's runtime bind would fail.
Authentication: if XRouter requires it, DAPPS_RHP_USER / DAPPS_RHP_PASS must match an entry the RHPv2 listener accepts.

Discovery / routing problems¶

"list_discovered_peers / list_neighbours empty, no traffic moving"¶

A fresh DAPPS install has no discovery channels configured by default - discovery is opt-in. Without a channel and an enabled beacon, you don't hear other nodes and they don't hear you. Two ways forward:

Manual neighbour: dashboard → Neighbours → add a row for the peer you want to talk to. This is the fastest path to "first message" - no discovery needed.
Discovery channel: dashboard → Discovery channels → add a channel for the bearer port DAPPS should beacon on. Set a sensible cadence (10 minutes for VHF FM is a reasonable starting point) and a per-channel airtime budget if you're on a shared band.

"I added a discovery channel but I'm not hearing anyone"¶

Check, in order:

Channel is enabled (the row's enabled flag).
Beacon cadence isn't unreasonably long (one beacon per hour means you hear nothing for an hour after start).
Other DAPPS nodes are actually transmitting on the same channel-key (same bearer port). A node beaconing on port 1 won't be heard by a node listening on port 0.
Airtime budget isn't exhausted. Dashboard → Discovery channels heading shows trailing-hour consumption; if it's ≥ 100 % of the global cap, beacons will defer. Either raise the cap or wait.

"Probes failing"¶

The probed-nodes table shows the recent failure reason. Common ones:

RETRYOUT: the bearer retried the connect to the remote callsign but never got a response. The remote isn't reachable on the link, or the bearer port for that peer is wrong (per-neighbour BearerPort or DAPPS_DEFAULT_BEARER_PORT).
Connect timeout: the connect went out but the protocol parser never saw the DAPPSv1> prompt. The peer either isn't running DAPPS, or you're connecting to the wrong application (their APPLICATION line might use a different command name).
TIMEOUT after DAPPSv1>: probe got the prompt but the session hung. Network is dropping packets mid-session, or one side has a serious clock skew.

"Forwarding loops"¶

The default passive-flood algorithm has a hop-count cap and won't loop indefinitely, but if you have a complex topology where it's mis-deciding routes, switch to the meshcore algorithm (DSR-style source routing) for more deterministic forwarding. DAPPS_ROUTING_ALGORITHM=meshcore + restart.

App-interface problems¶

"MQTT subscriber not receiving messages"¶

Check, in order:

The subscriber is connected to the right port (default 1883, configurable).
The subscriber is subscribed to the right topic (dapps/in/<app> for incoming).
Your MQTT client supports MQTT 5 user properties. DAPPS publishes dapps-id, dapps-source, dapps-ttl etc. as user properties - MQTT 3.1.1 clients will get the payload but not the metadata.
The subscriber is acking (dapps/ack/<app>). Without acks the messages stay in the local-inbox queue (dashboard → Local inbox panel) and re-deliver on the next subscription.

"REST submit returns 200 but message never arrives"¶

Look at the dashboard:

Outbound queue panel: is the message there? If yes, it's queued but the forwarder hasn't shipped it yet (next tick is at most 5 s). If no, the submit didn't actually write to the messages table - check the response body, it'll have an error.
Recently dropped panel: did it get dropped? If yes, reason will be there (usually TTL too short, or no route to destination).
Per-link state panel: is the link to the destination's first-hop neighbour actually working?

"TTL expired" drops¶

The default TTL on a submit is open-ended (no expiry). If you're seeing TTL drops, you're explicitly setting one. Either raise it on submit, or accept that mail-style multi-day delivery won't work with a sub-hour TTL.

Update problems¶

"Apply update button does nothing"¶

Three possibilities:

The dapps-updater.service / .timer unit isn't installed. systemctl status dapps-updater.timer should show active (waiting). If not, install per the Linux install page.
The marker file write succeeded but the timer hasn't ticked yet. Wait up to 60 s.
The updater ran but failed. journalctl -u dapps-updater.service will have the error.

"Update applied, but rolled back"¶

The new binary started but didn't pass the 60 s verify. Look at:

journalctl -u dapps.service --since '5 minutes ago' for the new binary's startup messages - there'll be a clear error.
The dashboard's update card - if rollback succeeded, the phase pill shows "rolled back" with the reason.

The previous binary is restored automatically; you don't need to do anything to recover. Investigate the new version's failure mode and either wait for a fix or stay on the previous version.

The poll cadence is hourly. To force an immediate re-poll, click Check now on the dashboard, or POST /Update/check, or call the check_for_updates MCP tool.

Investigating "where did message X go?"¶

A worked path:

Dashboard → Recently dropped panel. If the message id is there, the reason is the answer.
journalctl -u dapps.service | grep <message-id> - the decision-events ring is mirrored to the journal as structured log lines. Every step the daemon took with this id will be there: submit, queue insert, forward attempt, ack received / failed, etc.
MCP explain_why_message_failed if you have an assistant connected - it walks the same trail and produces a narrative.

If nothing turns up, the message was never submitted (typo on the topic / endpoint). Check the submitting application's logs.

Getting help¶

Dashboard not showing what you expect → screenshot it and open an issue. The UI is dense, behaviour-vs-expectation reports are useful.
On-air protocol question → see the protocol reference, then open an issue if it's not answered.
Bearer-specific weirdness (BPQ doing something odd, AGW edge case) → likely either a config issue documented above or a real bug; an issue with the BPQ logs + DAPPS journal is the right next step.