is it possible to recive the active SSLVPN connection via SNMP trap?
If yes what is the oid number?
There isn't a way to do this for SSLVPN via SNMP MIB. You can do it for IPSEC tunnels, though. You can track SSLVPN user has logged in/out via syslog, if you wish.
You can see all the SNMP MIBs here:
WatchGuard Customer Support