Tcpdump
tcpdump is a common packet analyzer that runs under the command line. It allows the user to display TCP/IP and other packets being transmitted or received over a network to which the computer is attached. Distributed under the BSD license,[3] tcpdump is free software.
Tcpdump works on most Unix-like operating systems: Linux, Solaris, BSD, OS X, HP-UX, Android and AIX among others. In those systems, tcpdump uses the libpcap library to capture packets. The port of tcpdump for Windows is called WinDump; it uses WinPcap, the Windows port of libpcap.