How to Fix Players Rejected at Join With an Invalid Connection Token

Players bounced at the connect screen with an invalid or expired token usually have a clock or reuse problem, not a network one. Connection approval has to validate the token correctly. Here is how.

How to fix it

1. Validate in the approval callback

Check the token's signature and expiry inside the server's connection-approval hook (NGO's ConnectionApprovalCallback or your transport's equivalent) and reject with a clear reason code on failure.

2. Use short, single-use tokens

Issue tokens from your backend that expire in seconds and are valid for one join. If a client retries with a consumed token, generate a fresh one rather than replaying the old, which the server correctly rejects.

3. Sync the clocks

Token expiry is time-based, so a server whose clock drifts from the issuer's will reject valid tokens. Run NTP on server hosts and allow a small skew tolerance when checking expiry.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.