Re: RE: Question about PV value from epics ioc

[Mark Rivers via Tech-talk <tech-talk at aps.anl.gov>]

• ... device is TCP socket connection on local network that call C code to get live data by using epics. 
  
• I intend to add a piece of C code to determine if the network connection of the device is down and then set the PV value to zero rather than always display the last data before its down when camonitor the PV. 

I want to make sure I understand what you are saying.  Do you mean you have an EPICS driver that talks to the device with TCP to get data?  Does EPICS send a query and then read the response?  If so, then you should be able to tell if the device is down by just seeing if the query timed out.

You should consider seeing the alarm status and severity of the records for the device if it is not available.  Then the OPI displays can indicate the alarm status, and not just a value of 0.

Mark

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From: lzfneu at live.com <lzfneu at live.com>
Sent: Monday, April 29, 2024 12:51 AM
To: Mark Rivers <rivers at cars.uchicago.edu>; tech-talk at aps.anl.gov <Tech-talk at aps.anl.gov>
Cc: lzfneu <lzfneu at live.com>
Subject: Re: RE: Question about PV value from epics ioc

 

Thanks for your reply. Actually I intend to determine if the device on local network (ip:192.168.1.100) connection is down and the device is TCP socket connection on local network that call C code to get live data by using epics. I intend to add a piece of C code to determine if the network connection of the device is down and then set the PV value to zero rather than always display the last data before its down when camonitor the PV. I want to consult you if I need to call C code, and if so, could you please show a demo on it. Thanks again.

 

From: Mark Rivers

Date: 2024-04-29 07:21

To: neu lzf; tech-talk at aps.anl.gov

Subject: RE: Question about PV value from epics ioc

One way to do this would be to use a standard drvAsynIPPort rather than ping.  If there is a port on another host which is almost always available then you could just periodically open that port and read from it, for example port 80 for http or port 443 for https.  If the asyn connection returns an error then you can assume the network is down.  This can all be done with standard EPICS records, with no need to call C code.

 

For example, you can periodically send a GET command to www.google.com on port 80.  If you get timeout or other error you know the network is down.

 

If you are trying to determine if a specific host on your local network is down then that might be different.

 

Mark

 

 

From: Tech-talk <tech-talk-bounces at aps.anl.gov> On Behalf Of neu lzf via Tech-talk
Sent: Saturday, April 27, 2024 8:16 PM
To: tech-talk at aps.anl.gov
Subject: Question about PV value from epics ioc

 

Hi,

 

I intend to establish a PV value from epics ioc depending on network connection status judging by the 'ping' command. If the network disconnected, the PV value is 0, otherwise  change to 1.

 

I want to consult you how to program the C file to implement this function by using epics, could you please show a demonstration on it. 

 

Any help will be appreciated and thanks in advance.