Syslogs are distinct from SNMP. Syslog messages are sent from the client to the server based on settings local to the host. The server passively listens - on udp/61 in the case of Prime Infrastructure.
SNMP is totally different in that there are both client-initiated traps and server-initiated polling. That happens (by default) via udp/161 and 162.
The two mechanisms use different agents at both ends of the conversation.