Hello,
I am using the check_telent command to verify that telnet is up on my Sun Solaris Server’s NETSC port. (The NETSC port is like a networked serial connection).
Nagios seems to be able to determine the port is up, but when I try to telnet to the port to manage the server, it hangs. It seems that Nagios is either keeping the session open all the time, or however it checks the port is causing it to hang up. Once I stop the monitoring and perform a reset on the port, things are fine.
Here is the pertinent configuration information from my Nagios server:
Telnet from Nagios Server
define service{
use generic-service
hostgroup_name solaris-remote-consoles
servicegroups solaris-remote-consoles
service_description TELNET
is_volatile 0
check_period 24x7
max_check_attempts 2
check_interval 1
retry_interval 1
contact_groups solaris-admins
notification_interval 120
notification_period 24x7
notification_options c,r
check_command check_telnet
}
‘check_telnet’ command definition
define command{
command_name check_telnet
command_line /usr/lib/nagios/plugins/check_tcp -H $HOSTADDRESS$ -p 23
}
Has anyone ran into an issue like this, or have any suggestions on how I might resolve this problem?
Please Note: I am very new to Nagios, and this could be something stupidly simple that I’ve done wrong. I apologize in advance. 
Thanks!