Experimental Physics and
Industrial Control System

• ... 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. 

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

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.