What is Wireshark ? 

Wireshark is the world’s foremost network protocol analyzer. It lets you see what’s happening on your network at a microscopic level. It is the de facto (and often de jure) standard across many industries and educational institutions.

Wireshark development thrives thanks to the contributions of networking experts across the globe. It is the continuation of a project that started in 1998.

you can download it from this page 

installation method shown below video from my youtube channel 

Wireshark has a rich feature set which includes the following:

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: tcpdump (libpcap), Pcap NG, Catapult DCT2000, Cisco Secure IDS iplog, Microsoft Network Monitor, Network General Sniffer® (compressed and uncompressed), Sniffer® Pro, and NetXray®, Network Instruments Observer, NetScreen snoop, Novell LANalyzer, RADCOM WAN/LAN Analyzer, Shomiti/Finisar Surveyor, Tektronix K12xx, Visual Networks Visual UpTime, WildPackets EtherPeek/TokenPeek/AiroPeek, and many others

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 platform)

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 analysis

Output can be exported to XML, PostScript®, CSV, or plain text