Hi! I was reading the Network Tables Protocol Specification (Revision 2.0), and I have a few questions about things that seem vague or missing from the document, if anyone could possibly answer them.
- Once an entry is created, can it be removed, or does it persist for the life of the server?
- If a server sends an Entry Assignment message to a client whose local network table already contains the ID, what is the client expected to do? Drop the request? Replace the existing entry?
- Can the length of arrays of values change?
- Is there a maximum length to arrays?
Thanks a bunch!
Alright, one more question. Can there be multiple entries with the same name?
I don’t believe that should happen. LV looks up the fully qualified name in the map and retrieves the field ID. If we wanted, we could add the type to the name and allow for a number, a Boolean, and a String with the same name. My interp of the spec was that if the name matches, it can change type and value and it would be better to have only one field with a given name. I can’t speak as confidently of the Java implementation.
It was meant more as a question of the spec, not a specific implementation (as I’m in the process of writing my own implementation). But it does seem unreasonable to have two entries with the same name.
Hah, so much for there only being one more question. If a client receives an Entry Update or Entry Assignment message with a sequence number less than the sequence number it has recorded, is it supposed to just drop it? I know a server ought to, but I’m not sure about a client.
I know how it goes. I must have asked the WPI folks twenty questions while implementing the LV one. And I’m typically telling you what the implementation does because honestly it is quicker for me to read than the spec.
So, in the same vein, for the LV implementation, the client takes the value update from the server no matter what, but the server takes client updates only if they have a newer seq#. Local updates increment the sequence number and protocol updates don’t. The assignments are basically the same, but they don’t ever increment.