Add ability to make SNR measurement

The QA401 application opens a default port on 9401. The ability to specify a port on the command line would be helpful for installations that are running in networks that might have certain ranges blocked.

HTML returns should specify "application/json" and force UTF-8

I've started making a simple web interface on top of this API, but the browser complains about missing CORS headers and refuses to connect:

Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:9401/Status/Version. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing).

More details here: https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSMissingAllowOrigin

Would it be possible to add the necessary headers to support my use case? Either by default or as an option?

If you want to test the web interface you can find it here: https://github.com/blurpy/qa401w

I received a report from a German user that QA401W isn't displaying anything, but that requests seem to go OK between the browser and QA401H. I was able to reproduce, and it looks like this after doing an acquisition:

There are no errors in the log of QA401H, and no errors in the console or network tab of the developer tools in the browser.

What happens is that if you configure your OS (at least on Linux) to some languages, the number format changes, and QA401H adapts. The browser does not though, so the JSON parser fails to interpret the numbers.

This is how it is normally for me:

curl -d "" -X PUT http://localhost:9401/Settings/AudioGen/Gen1/On/1000/0 
{ "SessionId":"0" }

curl -d "" -X POST http://localhost:9401/Acquisition 
{ "SessionId":"2290222104" }

curl http://localhost:9401/Phase/Seconds 
{ "SessionId":"2290222104", "Left":"0.00020784909723370925", "Right":"0.00020576029083909996" }

curl http://localhost:9401/ThdDb/1000/20000
{ "SessionId":"2290222104", "Left":"-102.82025498084323", "Right":"-102.46467345532238" }

curl http://localhost:9401/ThdPct/1000/20000
{ "SessionId":"2290222104", "Left":"0.0007227485864607289", "Right":"0.0007529503287253446" }

Floats use period as the decimal separator.

This is how it looks if I change the language to German:

curl -d "" -X PUT http://localhost:9401/Settings/AudioGen/Gen1/On/1000/0 
{ "SessionId":"0" }

curl -d "" -X POST http://localhost:9401/Acquisition 
{ "SessionId":"3592625235" }

curl http://localhost:9401/Phase/Seconds 
{ "SessionId":"3592625235", "Left":"0,0005415564663523863", "Right":"0,0005391615949382826" }

curl http://localhost:9401/ThdDb/1000/20000
{ "SessionId":"3592625235", "Left":"-102,99914694724458", "Right":"-102,03344721080657" }

curl http://localhost:9401/ThdPct/1000/20000
{ "SessionId":"3592625235", "Left":"0,0007080153160940537", "Right":"0,00079127535504247" }

Suddenly floats use comma as the decimal separator.

I started QA401H like this to reproduce:

LANG="de_DE.UTF-8" dotnet QA401H.dll

It looks like the JSON standard expect floats to use period as the separator:

• https://www.json.org/json-en.html (see number)
• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON (see PositiveNumber)

That also seems consistent with the behaviour the user experienced.
Is it possible to make QA401H return a consistent number format no matter the language?