How to Fix Peer Connections Failing With No Relay Fallback

If a subset of players can never join peer-to-peer no matter what, their NAT type likely blocks punchthrough. Without a relay there is no path. Add a fallback. Here is how.

How to fix it

1. Detect punchthrough failure

Give direct connection a bounded time to succeed. If both peers are behind symmetric NAT, hole punching will never complete, so a timeout is your signal to switch strategies rather than retry forever.

2. Fall back to a relay

On failure, route the session through a relay such as Unity Relay, a TURN server, or Steam Datagram Relay. The relay forwards traffic when no direct path exists, which is the only thing that works through symmetric NAT.

3. Prefer direct, accept relay

Use direct connections when available for lower latency and cost, but treat relay as the reliable fallback. Designing for direct-only guarantees a slice of players will never be able to play together.

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.