For example, to determine the status of a web server, monitoring software may periodically send an HTTP request to fetch a page.
[2] Status request failures, such as when a connection cannot be established, it times-out, or the document or message cannot be retrieved, usually produce an action from the monitoring system.
to the resident sysadmin, automatic failover systems may be activated to remove the troubled server from duty until it can be repaired, etc.
Site monitoring services can check HTTP pages, HTTPS, SNMP, FTP, SMTP, POP3, IMAP, DNS, SSH, TELNET, SSL, TCP, ICMP, SIP, UDP, Media Streaming and a range of other ports with a variety of check intervals ranging from every four hours to every one minute.
It can also include application monitoring, such as checking the processes of programs such as Apache HTTP server, MySQL, Nginx, Postgres and others.
As the information brought by web server monitoring services is in most cases urgent and may be of crucial importance, various notification methods may be used: e-mail, landline and cell phones, messengers, SMS, fax, pagers, etc.