i Remote PM800 comm issue

[ryanhuynh]

Hi guys,

We have a couple PM800 on same site connecting to Ignition fine and steady. Reading their 1700 registers are fine.

With 2 other PM800 on different sites, having trouble reading their registers. On Igntion gateway, keeps saying [hostname=10.235.38.110,port=502] Socket connection closed, DriverState was Connected. We also have citect talking to them but not stable either. 

Do you think it's because of Modbus over tcp is not good remotely via WAN? Or it's just PM800 is no good to modern HMI anymore? 
BR,
Ryan

[Charles_Murison]

Hello @ryanhuynh ,

Hard to say from just a description. One possibility may be the firmware version of the PM800 meter. What versions are and are not working? How old are the PM800 meters? Please note PM800 meters are now obsolete so there is no more active firmware being developed.

Regards,

Charles

[ryanhuynh]

Firmware is 2.4. They all are having same firmware including the working ones and the not working ones.

I've tried to wireshark it but don't see any sus trans

[ryanhuynh]

Also, I can't access their web server via WAN. I've traced up on wireshark and this is what I get:

[Charles_Murison]

Hello @ryanhuynh ,

Your post of Wireshark showing only Modbus traffic, It looks like every second request is getting answered. Given the filter only shows modbus traffic it is hard to know if meter never gets the request or if meter gets request and acknowledges but never responds or gets request, responds but response never gets to computer. 

Possibly to have the program sending the Modbus requests wait a short time before sending the next request?

Regards,

Charles

[ryanhuynh]

Seems like I can read its registers now suddenly. But still can't access its webserver via wan. If I'm on same site as the power meter is, I can access to its webserver no problem. 
I've checked with wireshark and every TCP request, the power meter send back a RST. 

[Charles_Murison]

Hello @ryanhuynh ,

I am glad to hear that you are able to read registers now. The webserver does sound strange behavior. Is the traffic to meter web server getting routed through the gateway as configured on the meter? Is the traffic within the subnet?

Regards,

Charles

[Robert_Lee · Accepted solution]

If you can access the webserver while on the same subnet but not externally, then either the meter's gateway isn't set properly (so it can't route requests outside of the subnet), or there is some piece of IT equipment which is blocking that port (like port 80 for HTTP for web access).

You may need to run wireshark on the same subnet as the PM800 to see what traffic it's seeing and any response it's sending out (and comparing that to a wireshark capture on the PC side of things when using the WAN).