I have installed a Hexing PLC meter and PLC Hexing DC, and configured the Hexing DC to connect on port 4059 (IDIS Concentrator). However, when I try to read the meter, it fails with message in Comms Monitor of 'Communication error?'

The Technical error message on the Meter Read Log is 'Mybe we should not have logged in? java.io.IOException: 0.0.96.1.0.255 GET failed? (d8h instead of C4h) 0.0.96.1.0.255', but when I check the check box 'Already Logged in on Cosem. Don't log in again' on Advanced Meter Settings, it gives a similar error 'Maybe we should have logged in? java.io.IOException: 0.0.96.1.0.255 GET failed? (d8h instead of C4h) 0.0.96.1.0.255'.

The D8 in the 3rd last byte typically means that the DC cannot get a reply from the meter.

If you get that reply from a GET message, e.g. 
 tx: 00 01 40 04 00 01 00 0D C0 01 C1 00 01 00 00 60 01 00 FF 02 00
 rx: 00 01 00 01 40 04 00 03 D8 80 01

(notice the C0 in the 9th byte, denoting a Cosem GET message)
That could also be that the customer's current login doesn't support that OBIS code, but if you get that reply from a LOGIN message, e.g.

then it definitely means that the DC cannot find the meter. (notice the 60 in the 9th byte, denoting a Cosem LOGIN message)

PLEASE NOTE, that the fact that you are receiving GREEN back from the 'meter', doesn't mean that you could communicate with the meter. It is in fact data generated from the DC, not from the meter.

To do that, join the wi-fi hotspot of the DC (default password is www.hxgroup.cn), and browse on your browser. (default at http://10.10.100.99:8080 )

Log in (default login is hexing and default password is 123456)

Click on Communication on the left hand menu, and click on the sub option of GPRS Parameters. Here you can set up the IP (of your pnpscada server), Port (has to be 4059), APN (can be 'internet' or whatever suits your SIM card for your situation), and pls put in the same IP for your Backup IP and the same Backup Port (4059), and click on Set.

After this is done, close the GPRS Parameters pane, and open it again, just to make sure that the settings have been properly taken, and then reboot the DC (typically, switch it off and on)

Open the DC in your web browser via its hotspot as detailed above, then click on the Debug button at the top. You have to go through another password authentication, for which the default password is also 123456. This will make your session go into Debug mode, which would enable new options in your configurator web site.

Go to Maintenance in the left hand menu, and the sub option of Gateway.

You will end up in a screen with 2 big text field columns. Above the left hand text field, would be some fields and 3 buttons.

Make sure the fields are:

MeterId (put in there your meter serial number, e.g. all 11 digits)

Class (should be 1)

OBIS (should be?0-0:96.1.0.255)

Attr (should be 2)

Then click on the blue 'Get' button.

In the right hand text field, it will start with something like:

->E6 00 0B 31 34 34 31 31 33 35 33 30 36 34 C0 01 C3 00 01 00 00 60 01 00 FF 02 00
then, if the meter exists and the DC can communicate to it, it will after a little bit of time also put a second line similar to this:

<-E7 00 0B 31 34 34 31 31 33 35 33 30 36 34 C0 01 C3 00 01 00 00 60 01 00 FF 02 00
but if the meter does NOT exist, or the DC CANNOT communicate to it for some reason, it will after some time put a second line like this:

<-E7 00 0B 31 34 34 31 31 33 35 33 30 36 35 D8 80 81

(notice the D8 in the third last byte)

In this way, the D8 return error can be verified using purely Hexing's own hardware, with our system not at all involved. Unless you can get this working, it is futile to try to get our system to communicate to the meter. If the DC doesn't see the meter, pnpscada would not be able to read the meter through the Data Concentrator. Please verify this communication first before calling us for support. And when talking to your manufacturer's support personnel, only mention using the mechanisms of the hardware and software of the manufacturer only, until you can get that working. Otherwise, it complicates the situation or they could blame us. But if the mechanism for which you seek support, only involves their own hardware and software, it is more difficult for them to shift the blame, and it makes it a lot easier for them to reproduce the problem and help you.