SNMP Traps

SNMP traps differ from other SNMP messages in that they are unsolicited messages sent by an SNMP agent when a predefined event has occurred.  For this reason, the SNMPII driver in Plant SCADA handles traps differently than other SNMP variables. 

Because there is no way of knowing in advance how many traps will be received by Plant SCADA , it is impossible to set up variable tags ready for each trap.  Instead, incoming traps are queued and read one at a time from the queue.

A set of seven tags, addressed as T0, T1, ...T6, is used to read each trap.