Nagios Support Forum

Other commands which do not depend on nsclient or nrpe.
How do the work? e.g check_pop,check_http,check_smtp etc
ie which ports do they use? how do they do check on services and how do they get the results.

Those plugins will use whatever port is associated with the service - 110 for check_pop, 80/443 for check_http, and 25 for check_smtp. They work by attempting a connection to the service and monitoring the response. If there is no response, it is typically assumed the service is not running. If there is a response, it can be used to determine which thresholds were hit. None of the checks you listed actually log in and run "service X status".

So if i get response 'CRITICAL - Socket timeout after 10 seconds ' when i use check_http then this would mean that access is denied on port 80/443?

tariqondego wrote:So if i get response 'CRITICAL - Socket timeout after 10 seconds ' when i use check_http then this would mean that access is denied on port 80/443?

The host could be unreachable or down as well. check_http can do more than just a port check - it it's most basic form, it is checking the server response time with the http protocol over the specified port. At its most complex configuration of options it can run uri string tests against a redirected site from the initial url specified in the check.

Try using the verbose verbose verbose argument, it'll give more detail as to what the plugin is doing: