Wireshark 2015

Wireshark is the world's foremost network protocol analyzer, and is the de facto standard across many industries and educational institutions.

Deep inspection of hundreds of protocols, with more being added all the time
Live capture and offline analysis Standard three-pane packet browser Multi-platform: Runs on Windows, Linux, OS X, Solaris, FreeBSD, NetBSD, and many others Captured network data can be browsed via a GUI, or via the TTY-mode TShark utility The most powerful display filters in the industry Rich VoIP analysis Read/write many different capture file formats Capture files compressed with gzip can be decompressed on the fly
Live data can be read from Ethernet, IEEE 802.11, PPP/HDLC, ATM, Bluetooth, USB, Token Ring, Frame Relay, FDDI, and others (depending on your platfrom) Decryption support for many protocols, including IPsec, ISAKMP, Kerberos, SNMPv3, SSL/TLS, WEP, and WPA/WPA2 Coloring rules can be applied to the packet list for quick, intuitive anal.