Experimental Physics and
Industrial Control System

"Kasemir, Kay" <[email protected]> · Mon, 9 Feb 2015 20:58:33 +0000

What Mark suggests could work, but the HTTP protocol is somewhat verbose and the exact response of the server could vary.

To emulate 

> curl http://10.95.101.75/bazaar?start=spectrum

you could try to send

GET bazaar?start=spectrum HTTP/1.1\n\n

.. and then ignore the response.

To emulate 

> curl http://10.95.101.75/data

you could try to send

GET data HTTP/1.1\n\n

and then you need to be prepared to parse a response that looks like

HTTP/1.1 200 OK
Content-Type: text/html
Server: Whatever
Cache-Control: no-cache
Pragma: no-cache
Content-Length: 97

.. the actual data..

You should try those GET commands from a plain telnet session to the server to see the exact response.

It might be easier to use for example python with urllib2 to communicate with the device, and then see the recent tech-talk discussion on how to get from python to EPICS:
* Use CA client library to write values from Python to a "real IOC"
* Use CA server library to serve the values from Python, i.e. it's like an IOC
* Serve data from python via a simpler TCP socket protocol, read into IOC via stream device.

Thanks,
Kay

On Feb 9, 2015, at 3:02 PM, Mark Rivers <[email protected]>
 wrote:

> This command should be:
> drvAsynIPPortConfigure("L0","10.95.101.75:80 HTTP",0,0,0)
> The HTTP means that drvAsynIPPort will handle the fact that the server will disconnect after each transaction.
>  
> You can’t use the “curl” command in your protocol.  You need to send the actual commands that the HTTP server requires.
>  
> It might be something like
> getData {
>     out "get data";
>     in "%\$1[^\r\n]";
>     ExtraInput = Ignore;
> }
> Mark
>  
>  
>  
> From: [email protected] [mailto:[email protected]] On Behalf Of Ana Malagon
> Sent: Monday, February 09, 2015 1:53 PM
> To: [email protected]
> Subject: using EPICS code with HTTP port
>  
> Hi,
>  
> I'm trying to use EPICs with a digitizer (www.redpitaya.com) which has a web interface - I can get the information using curl to download the website information:
>  
> curl http://10.95.101.75/bazaar?start=spectrum
> 
> curl http://10.95.101.75/data
>  
> but I'm a little confused about how to integrate these commands in an ioc. I've set up a StreamDevice template, and I thought I might be able to just send the curl commands by putting them in a record:
>  
> record(bo, "$(P)$(R)Start")
> {
>     field(DESC, "Start App")
>     field(DTYP, "stream")
>     field(OUT, "@devREDPITAYASTREAM.proto startApp $(PORT) $(A)")
>     field(ZNAM, "spectrum")
>     #field(PINI, "YES")
>     #field(VAL, "1")
> }
>  
> record(waveform, "$(P)$(R)Data")
> {
>     field(DESC, "Data string")
>     field(DTYP, "stream")
>     field(INP,  "@devREDPITAYASTREAM.proto getData(20000) $(PORT) $(A)")
>     field(PINI, "YES")
>     field(FTVL, "CHAR")
>     field(NELM, "32000")
> }
> with the corresponding entries in the .proto file being:
> startApp {
>     out "curl http://10.95.101.75/bazaar?start=%{spectrum}";;
> }
> getData {
>     out "curl http://10.95.101.75/data";;
>     in "%\$1[^\r\n]";
>     ExtraInput = Ignore;
> }
> When I run st.cmd, the host is configured to be the IP address of the red pitaya itself, using the HTTP port of 80:
> drvAsynIPPortConfigure("L0","10.95.101.75:80",0,0,0)
> I'm not sure if this is the right thing to do? In any case, when running st.cmd with asynTraceMask enabled I get a continuous stream of "reads"
> 2015/02/09 11:48:23.530 10.95.101.75:80 read.
> but it doesn't seem to respond to the commands I've made.
> Does anyone have any feeling for using Epics with HTTP commands? 
> Thanks!
> Ana Malagon

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System