Tcpdump and Netcat are one of the most useful utilities for Linux network debugging.
Some of the examples where I have found
tcpdump to be extremely useful are given below. In the next post, I will cover netcat.
Look for traffic based on IP address
Capture based on protocol
Capture based on interface
Capture filter based on certain port
Capture filter based on source port or destination port
Capture based on port range
Capture display in ASCII
Capture to a file