[SNMP4J] TreeUtils & DefaultPDUFactory

[Ronald Braswell]

I am attempting to use TreeUtils with a DefaultPDUFactory using GETNEXT
(the OID range is small).

I have set engine discovery for USM during the initialization of the
program to true.

The target uses V3 and USM.     I have successfully polled the target and
have successfully received traps from the target without specifying the
engineID when adding the UsmUser.

However, when I use TreeUtils as described above, it fails with 'Context
engine ID must not be null' at org.snmp4j.ScopedPDU.setContextEngineID()
line 69.

I am using SNMP4j version 2.5.

I notice using wireshark that a get-request is sent to the device to elicit
the report PDU from which it can discover the authoritative engine ID.
There are two packets sent from the manager to the target and the target
responds to each.   I would assume that the packets are encrypted getnext
packets with the responses appropriate to the requests.

When using the DefaultPDUFactory, do I need to specify the authoritative
engine for the user when adding the user to USM even though when polling
and I specify the PDU this is not necessary?

Ron