Re: using EPICS code with HTTP port

[Rod Nussbaumer <bomr@triumf.ca>]

Ana:

I doubt that your objective is do-able in StreamDevice alone. If it was 
my task, I would probably create an intermediate HTTP client using 
Python or Perl, and have it export the relevant data via a socket 
connection. The intermediate client could be on any host, including the 
IOC host, and would expose some SCPI-like command & query interface that 
StreamDevice can deal with easily.
Rod Nussbaumer
TRIUMF,
Vancouver, Canada.

On 02/20/2015 09:40 AM, Ana Malagon wrote:
> Hi all,
>
> Thanks very much! Dirk, thanks for the tip about using regular
> expressions - I am trying that now and hopefully can get it to work.
>
> I realized however that if I wanted to include the functionality of a
> json parser, such as https://github.com/json-c/json-c, that I would have
> no idea where to start with the StreamDevice template, as it only has
> the db and protocol file.
> I think I could do this with the old devGpib template, as the commands
> are defined in a C file, but does anyone know how I might get a JSON
> parser to work with StreamDevice?
>
> Thanks,
>
> Ana
>
> On Wed, Feb 18, 2015 at 4:37 PM, Mark Rivers <rivers@cars.uchicago.edu
> <mailto:rivers@cars.uchicago.edu>> wrote:
>
>     Hi Ana,____
>
>     __ __
>
>     I notice you have set the NELM field of the waveform record to
>     32000.  That is larger than the default value of
>     EPICS_CA_MAX_ARRAY_BYTES, which is 16K.  You need to set the value
>     of the environment variable EPICS_CA_MAX_ARRAY_BYTES to a value
>     larger than 32000 on both the IOC process and any EPICS channel
>     access client process.____
>
>     __ __
>
>     If that does not fix your problem then I would suggest the
>     following:____
>
>     __ __
>
>     - Create the drvAsynIPPort driver____
>
>     - Open an asyn record to the driver____
>
>     - Use the medm asynRecord.adl and asynOctet.adl screens____
>
>     - Turn on ASYN_TRACEIO_ESCAPE and ASYN_TRACEIO_DRIVER____
>
>     - Using the asynRecord send the command “GET /data”____
>
>     - Look at the asynTrace output to see what was sent and what was
>     received.____
>
>     __ __
>
>     Mark____
>
>     __ __
>
>     __ __
>
>     *From:* tech-talk-bounces@aps.anl.gov
>     <mailto:tech-talk-bounces@aps.anl.gov>
>     [mailto:tech-talk-bounces@aps.anl.gov
>     <mailto:tech-talk-bounces@aps.anl.gov>] *On Behalf Of *Ana Malagon
>     *Sent:* Wednesday, February 18, 2015 12:05 PM
>     *To:* Kasemir, Kay
>     *Cc:* tech-talk@aps.anl.gov <mailto:tech-talk@aps.anl.gov>
>     *Subject:* Re: using EPICS code with HTTP port____
>
>     __ __
>
>     Hi Kay, Mark,____
>
>     Thanks for the help - so I've tried both approaches (using pcaspy to
>     set up an IOC, and alternatively using HTTP in IPPortConfigure for
>     my streamDevice application) and am running into a stumbling block
>     with both.____
>
>     The problem is that when I request the data I always get an array of
>     0's back. Here's the syntax I'm using in the streamDevice IOC (and I
>     know the HTTP commands are correct because they work in a telnet
>     session):____
>
>     /===device.proto file===/____
>
>     /getData {
>          out "GET /data";
>          in "%\$1[^\r\n]";
>          ExtraInput = Ignore;
>     }/____
>
>     /====device.db file===
>     record(waveform, "$(P)$(R)Data")
>     {
>          field(DESC, "Data array")
>          field(DTYP, "stream")
>          field(INP, "@devREDPITAYASTREAM.proto getData(20000) $(PORT) $(A)")
>          field(PINI, "YES")
>          field(FTVL, "CHAR")
>          field(NELM, "32000")
>     }/____
>
>     For the pcaspy version, I have taken the tutorial file pysh.py,
>     which creates an IOC that processes shell commands
>     (https://code.google.com/p/pcaspy/source/browse/example/pysh.py) and
>     modified the OUTPUT to be of datatype "char" with a large count. I
>     have httpie installed, which is a library allowing me to run the
>     command 'http 10.95.101.75/data <http://10.95.101.75/data>' on the
>     command line to retrieve the data. However, when I do 'caput
>     MTEST:COMMMAND "http 10.95.101.75/data <http://10.95.101.75/data>"
>     and then 'caget MTEST:OUTPUT', I get an array of zeroes back.____
>
>     Does anything pop out as immediately suspicious?____
>
>     Thanks,____
>
>     Ana____
>
>
>
>     ____
>
>     __ __
>
>     On Mon, Feb 9, 2015 at 12:58 PM, Kasemir, Kay <kasemirk@ornl.gov
>     <mailto:kasemirk@ornl.gov>> wrote:____
>
>     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 <rivers@cars.uchicago.edu
>     <mailto:rivers@cars.uchicago.edu>>____
>
>       wrote:
>
>      > This command should be:
>      > drvAsynIPPortConfigure("L0","10.95.101.75:80
>     <http://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: tech-talk-bounces@aps.anl.gov
>     <mailto:tech-talk-bounces@aps.anl.gov>
>     [mailto:tech-talk-bounces@aps.anl.gov
>     <mailto:tech-talk-bounces@aps.anl.gov>] On Behalf Of Ana Malagon
>      > Sent: Monday, February 09, 2015 1:53 PM
>      > To: tech-talk@aps.anl.gov <mailto:tech-talk@aps.anl.gov>
>      > Subject: using EPICS code with HTTP port
>      >
>      > Hi,
>      >
>      > I'm trying to use EPICs with a digitizer (www.redpitaya.com
>     <http://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}
>     <http://10.95.101.75/bazaar?start=%25%7bspectrum%7d>";
>      > }
>      > 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
>     <http://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 <http://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____
>
>     __ __