GNURadio XMLRPC hints

If you are like me with a Windows computer using GNURadio in a VMware virtual machine, here's what you need to know to XMLRPC from a remote computer into your VMware instance on your local machine.

First, you need to make sure your VMWare instance is using a bridged connection. A bridged connection will present your VMware instance as a separate computer to your router giving it a unique IP address on the LAN (note: it is possible to use NAT, where the VMware instance appears on a private LAN to your PC, but the configuration gets messy for port forwarding)

Now, you should be able to use XMLRPC on your LAN. Download the example scripts from the GNURadio repository. In your virtual machine open up 'xmlrpc_server.grc' in grc. Open up the XMLRPC server block and change the IP address from 'localhost' to '0.0.0.0' and the port to whatever port you want to use.

If you use 'localhost' you will default to the local loopback device and will not be able to reach it from outside the VM instance. Execute the diagram and start the server - you should see a window pop up with a scope and FFT. 

You will need to get your VMware instances' IP address using ifconfig or some other tool. In my case it is 192.168.1.10.

On your client machine, download the example scripts and open up 'xmlrpc_client.grc' and edit the XMLRPC client blocks to use the IP address of your VMware instance and the same port

Execute the diagram and move the slider - you should see it update on the server.

Now, if you want remote access from outside your LAN we need to configure the router. First off for convenience' sake give the VMware instance a static or reserved IP address so that the MAC address of the VMware instance will always get the same IP address on the local network. Now, we can configure port forwarding, in which your router will take incoming traffic on a certain port and forward it to your virtual machine. My configuration looks like this:

Now you need to determine your routers' IP address or - better yet - set up a dynamic DNS address so that you can use a URL to always hit your router. I'm not telling you mine :) but I use a free one from freedns.afraid.org. Now go to your off-the-lan computer and update the XMLRPC client as above, but with your router IP address or dynamic DNS. If you did everything right it will work!

GNURadio: Getting audio to work in a VM

I've been going through a number of GNURadio tutorials and the waveform generator (signal sources) and display sinks have worked just fine. But then I hit a tutorial using the RTL-SDR stick as input and a flowgraph to process FM radio and an audio sink... and I get choppy audio! I started googling and most people blame the VM, but YouTube audio works just fine.

Then I stumbled across this post which contained the answer:

Ok, here are the contents of my ~/.gnuradio/config.conf:

[audio_alsa]
default_input_device = default
default_output_device = default
#period_time = 0.010                      # in seconds (default)
period_time = 0.100                      # in seconds
nperiods = 4                 # total buffering = period_time * nperiods
#verbose = false
verbose = true

The actual change I made was to increase audio_alsa/period_time from
0.010
to 0.100.  Play around with it until it works on your system.  My only
guess is that perhaps the default ALSA buffer sizes are small enough
that
they are often consumed by ALSA before GnuRadio will fill them.

Cheers,
-Remington

By default (at least in my Kali Linux VM) config.conf does not exist. Copy and paste the block of code to ~/gnuradio/config.conf.

For me, the above settings didn't work, but increasing period_time to 0.400 and nperiods to 16 and audio is crystal clear! Try the above settings, then mine, then something in between... hopefully this works!