Unhandled message 70 from the MS what does it mean?

Trying to connect to the master server. The client seems to get in touch with it and the dedicated server is already connected.

What does this error mean? Is there documentation of the MS error codes.

I think this is an error from the Facilitator (NAT punchthrough server). I have seen it once in a while in player logfiles when trying to connect via NAT punchthrough.

From looking through the Facilitator source, the error code appears to be:

/// NATPunchthrough plugin: Destination system is not responding to the plugin messages. Possibly the plugin is not installed. Bytes starting at offset 1 contains the RakNetGUID  destination field of NatPunchthroughClient::OpenNAT().
ID_NAT_TARGET_UNRESPONSIVE,	//70

(code snippet from Facilitator/Raknet/Sources/MessageIdentifiers.h)

Just wish I knew why it happened… and that the Unity client actually handled it somehow.

Only fix I can think of is an ugly one: scan the Unity output for this message, and when detected, treat it just like any NAT punchthrough failure.