What is "ngrep"

ngrep ( network grep) is a network packet analyzer written by Jordan Ritter. It has a command-line interface, and relies upon the pcap library and the GNU regex library.

ngrep supports Berkeley Packet Filter ( BPF) logic to select network sources or destinations or protocols, and also allows to match patterns or regular expressions in the data payload of packets using GNU grep syntax, showing packet data in a human-friendly way.

ngrep is an open source application, and the source code is available to download from the ngrep site on SourceForge. It can be compiled and ported to multiple platforms, it works in many UNIX-like operating systems: Linux, Solaris, illumos, BSD, AIX, and also works on Microsoft Windows.