Traffic Watcher

What does it do?

If you have ever used the "Net Traffic" tool in Interarchy, you will have some idea of what Traffic Watcher does. Basically, it intercepts any network traffic coming in or going out of your computer and allows you to see it in a plain and simple format.

How does it work?

Traffic Watcher uses a tool called "tcpflow" that was originally adapted by Jeremy Elson from the well-known UNIX tool "tcpdump". Thankfully Marc Liyanage managed to port it to OS X!

How do I use it?

Note: The first time you use Traceroute, Traffic Watcher or Packet Watcher, you will be asked to Authenticate. This is separate from the “Edit > Authorize” system; it is required only once for these tools – and it will do all three at once.

In Traffic Watcher, you have to choose the Network Interface you want to monitor. You do this by selecting one from the "Interface" popup menu. Net Tool Box assumes that "en0" is the Ethernet Interface, "en1" is the Airport Interface and "lo0" is the Loopback Interface (virtual). If you use IP over FireWire (which uses en1 also), you will need to specify this in the Net Tool Box preferences window.
You then need to decide what traffic you want to intercept. You do this by selecting "This Port" and typing the port number of the port that you want to watch. This is only available as a registered user.
Once you have set it up, click "Start" to begin. If it is the first time you have used Traffic Watcher this session it may ask you for your password. This is because the resources needed to run "tcpflow" are owned by "root". If you want Net Tool Box to remember your password for next time, you can set it to do so in the Preferences
When Traffic Watcher is running, it will precede any traffic with a header describing the sender and receiver of that packet.

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