Experimental Physics and
Industrial Control System

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):

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' on the command line to retrieve the data. However, when I do 'caput MTEST:COMMMAND "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]> 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]>