AutoReconnect behavior after a failed client upgrade in Photon Realtime

Question

AutoReconnect behavior after a failed client upgrade
Photon Realtime’s AutoReconnect feature is designed to restore a client’s connection to the same server and room following a transient network drop. The documentation, however, does not specify what happens when the client library upgrade fails and the client disconnects due to a protocol version mismatch.
The goal is to determine whether AutoReconnect will automatically attempt to re‑enter the same room after such an upgrade failure or if the application must explicitly call JoinRoom again. Key constraints include the potential for the server to reject the reconnection attempt because the client’s protocol version no longer matches the server’s expected version, which could leave the client disconnected or in an inconsistent state.
Uncertainty remains about the sequence of ConnectionState transitions, whether the client receives any callbacks indicating a failed reconnection, and if AutoReconnect will retry or abandon the attempt after a protocol mismatch.
Specific questions to investigate:

Does AutoReconnect automatically try to re‑join the same room when a client upgrade fails?
If the server rejects the reconnection due to a protocol version mismatch, does AutoReconnect retry or terminate the connection?
What callbacks or connection state changes are triggered during this scenario, and how can an application detect a failed reconnection attempt?

Tasadduq Burney · Answer

Answer to the core question
When a client upgrade fails (for example, due to a protocol version mismatch), Photon Realtime’s AutoReconnect feature will attempt to reconnect to the same server using the last known good connection parameters. It does not automatically re‑enter the room you were in, nor does it retry the upgrade. If the server rejects the reconnection because the client’s protocol version is no longer supported, AutoReconnect stops and the client remains disconnected until the application explicitly calls JoinRoom again.
Typical sequence of events

UpgradeFailed log message appears.
The SDK triggers a Disconnect event.
AutoReconnect (if enabled) starts a new connection attempt with the same ApplicationId and GameVersion.
If the server rejects the handshake because the protocol version is incompatible, the SDK emits OnConnectionFailed and OnDisconnected again, then stops retrying.
The application is left in a disconnected state; you must call JoinRoom (or OpJoinRoom) to re‑enter.

What callbacks indicate a failed reconnection?

OnDisconnected – always raised when the socket closes.
OnConnectionFailed – carries the DisconnectCause enum; a value of DisconnectCause.ServerRejected typically signals a protocol mismatch.
Logs containing "Failed to upgrade" followed by "Disconnect" confirm that the upgrade failure triggered the disconnect.

Practical steps to verify and fix the issue

Check the client configuration – Ensure that ApplicationId and GameVersion match the values configured on the Photon Cloud dashboard. A mismatch will cause the server to reject the connection outright.
Enable AutoReconnect – In code, set client.Settings.AutoReconnectEnabled = true (or the equivalent in your language). Without this flag, the SDK will not attempt to reconnect automatically.
Inspect logs – Look for a clear sequence: "Failed to upgrade" → "Disconnect" → "AutoReconnect started". If you see "Disconnect" without a preceding upgrade message, the problem may lie elsewhere.
Test a controlled upgrade – Run a client with an older SDK, trigger an upgrade to a newer SDK that the server does not yet support, and observe whether AutoReconnect attempts a new connection or stops after the first failure.
Handle re‑join logic – In your OnDisconnected handler, call client.OpJoinRoom (or the higher‑level JoinRoom API) to re‑enter the room after a successful reconnection.

Assumptions and caveats

These observations are based on Photon Realtime SDK 7.x and earlier. Newer releases may have modified upgrade handling logic.
AutoReconnect does not recover from server‑side protocol incompatibilities; you must coordinate server upgrades with client releases.
Repeated disconnects in a flaky network environment can trigger many reconnection attempts, potentially hitting server rate limits.

Missing diagnostic detail
To refine the recommendation, could you confirm whether the client sends the same GameVersion during the reconnect attempt, or if it resets this value automatically after a failed upgrade?

AutoReconnect behavior after a failed client upgrade in Photon Realtime