Is there any documentation on what the internal cause codes seen in the lightstreamer log mean?

I'm following this to see why the below happened and what callback is triggered on the client when LS server destroys a session:

02-Sep-11 08:22:25,320|INFO |LightstreamerLogger.requests |FOR PUMPS PARKING DESTROYER|Closed session S702f5726fd2822bT2156944 with internal cause code: 38

This looks like a some kind of LS session timeout? The circumstance is a browser sitting idle receiving live stock prices for several hours, then the user returns to the browser (whose session is still active) and he isn't getting LS updates, which is confusing

Does this do callback onServerDeny, or maybe result in the client attempting a re-subscribe that in our circumstance would result in onServerDeny?