Tuesday, May 13, 2014

Raspberry Pi fun...

I received a Raspberry Pi for Christmas and I hadn't found a good use for it yet - until now!  Well, sort of.  I at least found something kind of fun to do with it...as long as your definition of fun is very loose.

I've been using RabbitMQ at work, and I found someone's post about running RabbitMQ on their Raspberry Pi.  "A ha!", I thought. "I'll load interesting messages onto channels, and then I can write an Android app that will fetch the messages.  It will be so amazing!"  The problem is that I couldn't think of what type of data I would want to get.  I ended up deciding to capture all IP addresses on my home network using nmap.

I installed RabbitMQ on the Raspberry Pi by following someone's blog post (very well written!), and then added a user and virtual host. I then wrote a script and some Java code to log all of the IP addresses on my local network. We have a number of devices that connect and disconnect throughout the day, so there would be enough of a change as time goes on to make it interesting.

The script runs nmap to get the network info, and then it calls some Java code that publishes the info to a RabbitMQ channel. I decided to use Java because it was the easiest for me to write the code. I might redo the code in Python once I get some experience with Python.

The nmap command is pretty straight forward: 

sudo nmap -oX myscaninfo.xml

The -oX parameter tells nmap to output the results in xml format.  

The IP address with the CIDR (Classless Inter-Domain Routing) value at the end ( specifies the IP addresses to scan.  In the example above, it would mean the following: is the starting IP address. We would then mask the address with 24 1 bits =>  255 is what 11111111 equals (-1 due to 0 based index).  That means that we would want to view all IP address that are in the unmasked range - to

The Java code parses the XML and pulls out all the address info. It then pairs the IP address with a MAC address, and publishes the data to RabbitMQ.

The next step will be to create an Android app to read from the channel and display the data.

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