Re: Basic PVAccess question

[Marty Kraimer via Tech-talk <tech-talk@aps.anl.gov>]

On 2/27/19 6:27 AM, will.rogers--- via Tech-talk wrote:

I am looking at the exampleCPP repo for EPICS7.


When I run helloRPC I can use pvcall and p4p as a client successfully.


When I run pvDatabaseRPC, I can't use either, and I get the following message:

ChannelRPC not supported


HelloClient.cpp (helloRPC) and positionClient.cpp (pvDatabaseRPC) both use an RPCClient to communicate the server.


I think I don't understand fully. Can anyone clear this up for me?


Cheers,

Will

Let me answer helloRPC first.
This is a really simple example of using channelRPC.
It has a server that only implements channelRPC and nothing else, i. e. it is not an IOC.
Thus channelGet, channelPut, and channelPutGet requests will all fail.
It is started as follows:

mrk> pwd
/home/epicsv4/masterCPP/exampleCPP/helloRPC
mrk> bin/linux-x86_64/HelloService
pvAccess Server v6.1.0

It has a client that only issues a channelRPC request.
It is run via

mrk> pwd
/home/epicsv4/masterCPP/exampleCPP/helloRPC
mrk> bin/linux-x86_64/HelloClient
Hello anonymous
mrk>

pvDatabaseRPC is a much bigger example
Since you are running the example look at exampleCPP/documentation.
It has documantation about all the examples.
In particular look at exampleCPP.html and pvDatabaseRPC.html.

pvDatabaseRPC.html says the following:

pvDatabaseRPC is an example of a pvAccess server that has a PVRecord that supports Channel RPC as well as the usual operations: Channel Get, Put and Monitor and get introspection data.

It illustrates synchronous and asynchronous RPC services, selecting services based on the supplied pvRequest and using EPICS V4 to talk to an existing object which has no knowledge of EPICS and call its methods, so creating distributed objects.

It represents a device which has a 2D position setpoint and readback as well as a state. The device can be controlled through a client using RPC commands to move through a sequence of points as well as conventionally by putting to the setpoint.

Also have you seen

https://mrkraimer.github.io/website/developerGuide/developerGuide.html

I hope this help.

Marty Kraimer