check_tcp

[Stuart Henderson]

On 2021-02-25, Werner Flamme <werner.flamme at ufz.de> wrote:
> Am 2021-02-24 um 10:57 schrieb Piotr Kilar:
>> Hello,
>> I'm using Your check_tcp plugin and i'm need to monitor stunnel, but go=
> t
>> one issue.
>> When stunnel certificates are expired or remote host is rejecting my
>> connection check_tcp is showing me OK - port is open, and it is true
>> because there is open local tcp port binded by stunnel process. But whe=
> n
>> using f.e. telnet i can see that "Connection closed by remote host" and=
>  see
>> why in stunnel logs. Is it possible to adapt check_tcp to show CRIT in =
> that
>> cases (immediate port closure by remote host)?
>
> Hi Piotr,
>
> check_tcp does exactly what its name says: it checks a tcp port. Since
> the port is open, the result is OK.
>
> If you want to check on an SSL certificate, you should use other
> plugins, like check_ssl_cert. Or try to initiate some traffic over the
> port, whatever software is at the back end of the stunnel (like, mail,
> web server, ...).

Use check_tcp with -S and -D options, see the help text (check_tcp -h).