These ZMQ receivers can be opened in GNUradio and used to modify a signal into a visible and audible format. The virtual machines used for the virtual wifi can be used, but performance will be poor. If possible, it is recommended to use Gnuradio on your local computer for better performance.
The server is sdr.rfhackers.com ports 6550-6570. By modifying the 'port' variable, you can access each of the different challenges.
Note: If you're on a low bandwidth connection, it's recommended to save the IQ stream to a file first, then decode the information from the file. There is a file sink in 3.8 and a wav file sink in 3.10. They are disabled by default, right click and enable to save to a file and use in your favorite program.