vpn:/etc/zabbix# zabbix_agentd -p | grep listen
net.tcp.listen[80]                            [m|ZBX_NOTSUPPORTED]
pptp.listen                                   [t|1]
l2tp.listen                                   [t|1]

==========
root@zabbix:~# zabbix_get -s85.21.247.88 -p10050 -k"pptp.listen"
2
root@zabbix:~# zabbix_get -s85.21.247.88 -p10050 -k"l2tp.listen"
2
==========
 less /var/log/zabbix-agent/zabbix_agentd.log | grep pptp
  6722:20120201:153842 Run remote command [/etc/zabbix/pptp.sh] Result [1] [2]...
  Sending back [2]

 less /var/log/zabbix-agent/zabbix_agentd.log | grep l2tp

  6722:20120201:153901 Run remote command [/etc/zabbix/l2tp.sh] Result [1] [2]...
  Sending back [2]