ucd-snmp (now known as net-snmp) is a thoroughly kick ass system comprising an extensible snmp agent and various tools relating to the snmp protocol. Works on most unices and windows platforms.

Idiot guide to getting net-snmp running

1. Get the latest release of net-snmp from sourceforge
2. Install according to your platform.
eg. for most unices, get the net-snmp-x.x.tar.gz source file and do
gunzip ucd-snmp-x.x.tar.gz; tar xvf ucd-snmp-x.x.tar; cd ucd-snmp-x.x
./configure '--with-mib-modules=host'
go root and do make install
3. start the snmpd demon
/usr/local/sbin/snmpd (as root)
4. Query the snmpd demon
snmpwalk public
5. You can take lines from the output of snmpwalk and use them in snmpget, eg.
snmpget hostname public sysUpTime.0
6. To receive trap traps
as root, do
/usr/local/sbin/snmptrapd -P
7. You can use shell scripts or the command line to send traps eg.
snmptrap -v 1 sender_hostname public system receiver_hostname 6 0 '' system.sysContact s hello_world
- this will send a v1 trap saying 'hello world'

Apologies for the dull write up, but that little lot took me about a month to figure out. I am l4m3 with computers.