How can i monitor my server?

[Carstea Catalin]

It is possible to monitoring activity of freebsd -services ( apache, mysqld, 
squid, named, postfix ) if it is down or up via internet with some scripts?
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I want to know if this services is running via internet ( web page - if it 
is possible) .
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I belive the response is in crontab with somethings to verify if the 
services is running.
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Sorry for my english.
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Pls help me! Tks!