Monitoring software
 

I ever used a windows program called "What's Up" to Monitor the availability of services of the servers and other equipments like routers.
Is there any software similar to this in Linux?

not a clue what "What's up" is... (please don't expect us to know what functionality other applications provide) I use opennms for device polling, and have also used nagios and jffnms with some success. no idea what your requirements really are though.

a packet sniffer maybe...
 

Is that what you were asking about?