Incorrect Device ID in `_` Field When Using android client

[sudofox]

Yes I wrote the following with ChatGPT but I swear that I have triple-checked that it is fully accurate.

Notably, traccar client on android doesn't seem to be using OsmAnd?

---

When using the official Traccar Android Client, the client’s JSON payload includes a field named "_" that contains a generated querystring-like fragment. This fragment includes an id= value.

In at least one case, the id= inside the "_" field does not match the device ID configured in the app, and instead contains a different numeric value.

Example (anonymized):

{
  "location": {
    "timestamp": "…",
    "coords": { … },
    "is_moving": true,
    "odometer": 0,
    "battery": { … },
    "activity": { … },
    "extras": {},
    "_": "&id=71881261&lat=…&lon=…&timestamp=…&"
  },
  "device_id": "configured-device-id"
}

The server interprets the id= from the "_" field and logs:

Unknown device - 71881261

The configured device ID (configured-device-id) is present in the JSON, but the value in "_" is different and appears to be used instead.

Issue:
The "_" field sometimes contains an unexpected or incorrect id value, which leads to the server rejecting the packet due to a mismatched device identifier.

[sudofox]

Here is an (anonymized) log entry from the traccar server:

2025-11-29 19:58:43  INFO: [Td1a4e66e: osmand < 127.0.0.1] POST / HTTP/1.1
Host: [redacted]
x-forwarded-for: 2601:405:4180:f780:8df7:ce8d:5e6f:e82c, 2400:cb00:1049:1000:8f28:6dcf:99dc:6b06
content-type: application/json; charset=utf-8
user-agent: okhttp/3.12.13
accept-encoding: gzip, br
cf-ray: 9a64ae6f9f9ae805-EWR
cdn-loop: cloudflare; loops=1
CF-Connecting-IP: 2601:405:4180:f780:8df7:ce8d:5e6f:e82c
CF-IPCountry: US
CF-Visitor: {"scheme":"https"}
X-Forwarded-Proto: https
X-Forwarded-Host: [redacted]
X-Forwarded-Server: [redacted]
Content-Length: 419
Connection: Keep-Alive

{"location":{"timestamp":"2025-11-29T19:16:24.764Z","coords":{"latitude":0.0,"longitude":0.0,"accuracy":10.6,"speed":-1,"heading":-1,"altitude":244.31},"is_moving":true,"odometer":0,"event":"motionchange","battery":{"level":0.8,"is_charging":false},"activity":{"type":"still"},"extras":{},"_":"&id=71881261&lat=0.0&lon=0.0&timestamp=2025-11-29T19:16:24.764Z&"},"device_id":"device-xxxxxxxx"}
2025-11-29 19:58:43  WARN: Unknown device - 71881261 (127.0.0.1)

[tananaev]

1. What version of Traccar are you using?
2. Have you changed the device id in the app?

[sudofox]

1. 6.6
2. Yes. The API call included both the old default-generated ID and the new one.

[tananaev]

You should upgrade Traccar.