jNetMap
jNetMap is a graphical tool for keeping an eye on all the devices in your network. It can discover all the devices connected to the network and you can also add new ones, such as an external webserver.
You will just have to draw the connections between the devices and your netmap is ready to go.
jNetMap will check every 5 minutes if your devices are still running, and you can create alert scripts
to notify you if they are not. You can adjust the interval in the upper right corner of the screen.
The color of the lines connecting your devices indicate the availability of said device.
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License
GNU General Public License (GPL)