Analyzing network traffic with Tshark
Terminal Analyzer
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The simple and practical Tshark packet analyzer gives precise information about the data streams on the network.
When the system logs fail to provide information on problems, or if you simply want to know what is happening on the network, it is worth taking a look at the data stream. Tools such as Tcpdump [1] or Wireshark [2] let you listen on the network to study and troubleshoot network problems. Tcpdump is the tool of choice for gurus and professionals, but Wireshark appeals to many users because of its powerful GUI. If you prefer to work at the command line, or if you don't have time to grapple with Wireshark's elaborate user interface, you can use Wireshark's little brother Tshark [3] to sniff packets in a terminal window.
Like other packet sniffers, Tshark switches the interface into promiscuous mode to listen for network packets. In promiscuous mode, the network adapter hands over all the packets to the operating system, instead of just the ones addressed directly to the local system with the MAC address. Tshark can therefore listen to all the traffic on the local network, and you can use filtering commands to narrow down the output to specific hosts or protocols that you want to study.
Many Packages, Many Privileges
You can install Tshark via the command line or using a graphical tool of your choice. I used the 64-bit version of Tshark 1.10.6 on Ubuntu 14.04 for this article. Tshark is included with most other major distributions and accepts the same parameters, so you can use a different flavor of Linux and complete the installation with the package manager of your choice. On Ubuntu, you first need to update your system (Listing 1, first two lines). Then, install the program using the package manager (last line).
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