[AGENT++] The trap is received but callback isn't executed?

[Dario maljur]

Hello.

I'm currently learning to work with traps and informs. I have defined
callback function and registered it in Snmp object. I have set oids (well
just one)target and target listen address, and started poll thread. Agent is
normally sending traps with 

"publicUser,SNMPv3_usmNoAuthProtocol, SNMPv3_usmNoPrivProtocol and with no
passwords. The manager is set to the same user.

 Logging mechanism informs me that trap generated by agent is received, and
parsed, but callback function that I registered isn't initiated. How come?

 And I have one more question about start_poll_thread(). Can it be started
multiple times? Because it seems that I can start it many times and the
return value is always true.