From the OpenNMS server, you can use the snmp-request tool in the $OPENNMS_HOME/bin directory.
For example, support that the IP address of the target node is 192.168.0.8, the community string is public, and the SNMP agent is enabled using the default port with SNMPv2, the command should look like this:
/opt/opennms/bin/snmp-request -c public -v 2c -Ow 192.168.0.8 .1.3.6.1.2.1.1
This is equivalent to execute an snmpwalk like this:
snmpwalk -One -v 2c -c public 10.0.0.1 system