Experimental Physics and
Industrial Control System

Dirk Zimoch <[email protected]> · Fri, 20 Feb 2015 09:42:41 +0100

Hi Ana,

When I want to test a new network attached device, I often start with a

simple telnet to see what happens.

telnet 10.95.101.75 80
GET /data
[2x return]

(This will probably not work).

I expect that you need to type:
GET http://10.95.101.75/data
[2x return]

As soon as it works, put the necessary commands into StreamDevice.

On 18.02.2015 19:04, Ana Malagon wrote:

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 <[email protected]
<mailto:[email protected]>> 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 <[email protected]
    <mailto:[email protected]>>
      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: [email protected]
    <mailto:[email protected]>
    [mailto:[email protected]
    <mailto:[email protected]>] On Behalf Of Ana Malagon
     > Sent: Monday, February 09, 2015 1:53 PM
     > To: [email protected] <mailto:[email protected]>
     > 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}";;
     > }
     > 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

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System