[Skimmertalk] Follow-up on Skimmer with rtl_hpsdr (dongle driver)

[John Ackermann N8UR]

Well, I think that Skimmer Server and the N1GP/NO1D rtl_hpsdr driver 
*want* to work together, but just can't quite make it work.  Here's 
where things stand now.

1.  I was able to connect the Skimmer Server to a Red Pitaya and capture 
spots, so the Skimmer (and RBN Aggregator) functionality works.

2.  I was able to connect to the rtl_hpsdr box (Raspberry Pi 3 with from 
1 to 4 RTL-SDR.com dongles connected) with the HDSDR receiver software 
and successfully tune and listen to various frequencies with one dongle 
(though the tuning was a little flaky -- sometimes I had to stop and 
then restart HDSDR to get a new frequency to "stick".

3.  I was also able to receive 4 bands simultaneously from rtl_hpsdr and 
4 dongles using a Gnuradio with the N5EG Hermes receive block.

So, both ends of the system seem to work.  But when I try to connect 
Skimmer Server to rtl_hpsdr, this is what happens:

1.  On the first attempt after a reboot of both systems, Skimmer Server 
says "Too Many Receivers Connected".  rtl_hpsdr shows a discovery 
request, and receipt of a "Stop" command (but not frequency set or 
"start" commands).

2.  If I close Skimmer Server and restart it, on the second attempt I 
usually get a "divide by zero" error window, but Skimmer starts.  This 
time it usually says "No HPSDR Device Found".

3.  If I then restart rtl_hpsdr and restart Skimmer (without rebooting 
the machine), Skimmer will usually connect.  BUT -- as far as I can 
tell, it's not receiving/decoding any data.  I send CQs (into a dummy 
load) but nothing shows up.  I don't know how to tell anything further 
about where the receiver is tuned, or whether Skimmer is actually 
receiving spectrum.

I suspect there is something in the startup handshake sequence between 
the two programs that is not correct.  If I can get Wireshark to work on 
the Raspberry Pi, I'll try to capture the connection sequence to see 
what's going on.  Wish me luck...

73,
John