Extend to RSP_TCP server protocol for remote SDRPlay devices

[nmaster2042]

SDRplay team has developed an extended version of RTL_TCP called RSP_TCP : https://github.com/SDRplay/RSPTCPServer

There is the -E (extented mode) to control specific RSP devices settings + 12 bits instead of 8 from original RTL-SDR.

This would bring access to remote sdrplay family devices from Soapy.

[zuckschwerdt]

Sounds good. We'd just need to detect the RSP_CAPABILITIES_MAGIC on the first frame received and then switch to use the extended mode options.

There still isn't any back channel and no flow control. I was thinking about adding a best-effort flow control transparently, basically a command to pause/resume the stream according to (de-)activateStream API. Not sure if that would help much though (you could keep a receiver open and paused without spending time and bandwidth in the sender).

[nmaster2042]

I don't know if it can help for dev work but there is the Extio RSP_TCP source code here: https://github.com/SDRplay/ExtIO_RSP_TCP where is implemented the specific client part.

[zuckschwerdt]

Thanks, always good to confirm that we got the right idea.
I guess it will more difficult to install an SDRplay test environment than to implement the extended protocol ;)

[nmaster2042]

You're right.
Here I have RSP 1A, 2pro, Duo & DX for tests.
I can open a rsp_tcp server for you to try ?
One device at a time.
FTTH here so it should work, even if it doesn't for higher BW.

[zuckschwerdt]

I'll add a branch with basic support for the extended mode. Maybe it'll just work :)

[nmaster2042]

There is an implementation of RTL_TCP / RSP_TCP as plugin from SDRAngel.

https://github.com/f4exb/sdrangel/tree/master/plugins/samplesource/remotetcpinput

It could help add the rsp_tcp protocol in the Soapy driver ?

In this plugin, the 2 protocols are supported RTL0 for rtl_tcp and SDRA for rsp_tcp with it's enhanced features.