Mognet - Java Based Wireless Sniffer

Mognet is a simple, lightweight 802.11b sniffer written in Java and available under the GPL. It features real time capture output, support for all 802.11b generic and frame-specific headers, text mode capture for GUI-less devices, and loading/saving capture sessions in libpcap format.

Mognet requires a Java Development Kit 1.3 or higher, and a working C compiler for native code compilation. Your wireless card must support monitor mode, which most (but not all) do.