Check status of IMAP server
The Internet Message Access Protocol (commonly known as IMAP) is an Application Layer Internet protocol that allows an e-mail client to access e-mail on a remote mail server. The current version, IMAP version 4 revision 1 (IMAP4rev1), is defined by RFC 3501. An IMAP server typically listens on well-known port 143.
I had configured a Dovecot server with IMAP status, for many users , so I needed a mechanism to check if the server is responding on client requests during the high traffic. I wanted to do this using a Cron job and a simple script. This script will telnet to the IMAP port on the Linux server and check the status every 60 seconds. This is how often I configured the Cron job, it can be configured on every 5 minutes or so.
Now let us take a look on this simple code I wrote:
#!/bin/bash
#http://itstuffallaround.blogspot.com/
#program to check if connection is possible with Dovecot and log errors and success full connections
if telnet localhost 143 </dev/null 2>&1 | grep -q Escape; then
echo "Connected Dovecot on $(date)" >> DOVSTATUS.txt
else
echo "No connection to Dovecot on $(date)" >> DOVSTATUS.txt
fi
The simple BASH language script is constructed of a single loop, that telnets to port 143 and returns the status of the service to a dovstatus.txt file.
The parameter /dev/null 2>&1 was very useful to me, because it will disable returning the on screen prompt for action on telnet, and Escape the login sequence because it is not neccessary, it will redirect both the output and the error streams. Even if your program writes to stderr, that output will not be shown. After this rename the file as .sh and add the execute perrmissions on it. Configure it as a cron job and wait for the results in the dovstatus.txt file.
Feel free to code more!
