For UNIX:

Install Java2 Runtime Environment, libpcap, and Jpcap.

Download the latest JpcapDumper.

Input the following in the command line.

java -jar JpcapDumper.jar

For Windows:

Install Java2 Runtime Environment and WinPcap (packet capture library for Windows).

Download JpcapDumper for Windows, and extract the zip file.

Double-click JpcapDumper.jar.