How to monitor the network activity of a Java application on Linux in detail?

Question

Let's say I have a third-party java application.

It is a .jar which I run in a usual manner: java -jar app.jar

How can I monitor what it sends and gets through the network on a Debian-based system?

I would like to know which servers it connects to and what data it sends and gets.

Answer 1

Use netstat. Note that it will only provide the socket information. For more detailed analysis, you can use wireshark.

More info: http://en.wikipedia.org/wiki/Netstat, http://linux.die.net/man/8/netstat, and http://linux.die.net/man/1/wireshark