PSN Server: What to send if no tracker available

looki

Hi,
I read the protocol description (v2.03) but cannot find information about what to send if no tracker is online/available in my system. Should I send empty PSN_DATA_PACKETs, or no PSN_DATA_PACKETs at all? If I should send PSN_DATA_PACKETs, should it contain an empty PSN_DATA_TRACKER_LIST chunk, or no PSN_DATA_TRACKER_LIST chunk at all? Same question regarding PSN_INFO_PACKETs.

Best,
Lukas

strinh

Hi Lukas,

The decision as to what to send lies entirely with the server’s implementation and is generally application specific.
If you are writing a PSN server for your application, it is up to your implementation to specify what happens when there is no data on the server. You PSN client should also ‘know’ how to interpret the data that is sent ( or not ) from your server’s implementation.
There are a variety of application specific strategies that have been used with PSN data for example

Dead reckoning ( keep same position/velocity until new data arrives )
Return to Zero ( go back to some safe place when data does not arrive in a specified time window )

As a data protocol PSN can only specify the form and packaging of the PSN data. It does not specify how that data
should be interpreted and does not impose any form of sequencing or grammar for application specific uses.

Best
Stéphane

looki

Thanks for the quick and helpful answer.

The reason I am asking is because our product is used by a PSN client that throws errors if any PSN chunks are missing (which happens in the case of no available/online trackers as mention above).

I was unsure if I missed a certain rule or specification - reading your answer it looks like the client should handle such edge cases better, shouldn’t it?

Best,
Lukas

strinh

Hi Lukas,

For sure a PSN client should be robust, however I would not throw any implementation under the bus at this point. PSN is used in a variety of workflows and environment, it is often implemented on top of an existing solution (say by an automation vendor) and requirements are sometimes a bit fuzzy on the client side 🙂. If you’re writing for a specific vendor perhaps you can get in touch with them and try and sort out what the client expects.

Hope this helps.
Best
Stéphane