Remote OPC Server Connections

(I hope I have posted this in the correct area. If not, I suppose you can smack me in the head with a large trout.)

I have a PC running RSLinx Gateway. This PC is on my private "SCADA" network (192.168.1.x).

On any PC on the private LAN, I have no problem connecting to the remote OPC server and getting live data from the DH+ Network.

In the same building I have a "corporate" network that uses public IP addressing, and I need to get PCs on that network to connect to the remote OPC server as well. And that's where I run into problems. Simply put, the OPC client will not connect.
I've opened the appropriate ports in the hardware firewall isolating the private network. I verified my NAT settings in the firewall were correct. No connection.

I temporarily inserted an "Allow everybody and his brother to connect" entry into the firewall. No connection.

I set permissions and security in DCOM to let anyone connect. No connection.

I've tried multiple OPC test clients, which give me slightly differing errors:

"Connection to the server failed. ~RSLinx OPC Server ~"

"Runtime Error '-2147022986' The object exporter specified was not found."

Error: -2147022986, Method 'Connect' of 'IOPCAutoServer' failed.

And again, the test clients work as expected on the private network, the errors only happen when I try to connect from our WAN to the server.

Does anyone have any suggestions I might try to get this up and running?

Thanks,

jep

is your private network managed by a domain? if so is this domain a child to the corp domain? if so, is the connecting user the same?

snguyen said:

is your private network managed by a domain? if so is this domain a child to the corp domain? if so, is the connecting user the same?

Click to expand...

No, the private network is not managed by a domain.

jeparham,

what bridges the two network? an appliance router or the corp domain?

snguyen said:

jeparham,

what bridges the two network? an appliance router or the corp domain?

Click to expand...

There's a LinkSys RV082 10/100 8-port VPN Router bridging the two networks.

I didn't mention before, and it may not matter, but I have installed RSLinx Lite on the PCs on the corporate network, and using it every one of the PCs can see the Gateway machine and browse every PLC that resides on the DH+.

rslinx light will not server data outside of RSLogix. sorry.

snguyen said:

rslinx light will not server data outside of RSLogix. sorry.

Click to expand...

Yeah, I know Lite won't. I just used Lite to see if it was a firewall or a DCOM issue.

On my private network PCs I don't even have RSLinx running, and the OPC clients will connect to the Gateway box and pull the data.

Did that make any sense?

can you put one of the private network pc on the corp side and test? if this doesn't work i think its the firewall.

good luck.

snguyen said:

can you put one of the private network pc on the corp side and test? if this doesn't work i think its the firewall.

good luck.

Click to expand...

My corporate issued laptop's cabled NIC is set up to use the public IP space. It also has a wireless NIC.

I can't get the OPC client to connect to the remote server using the public IP on the laptop.

So I setup the wireless NIC to connect to the private network via a WAP.

Using the wireless NIC, I was able to connect the OPC client to the remote OPC server. I don't know why, but as long as the wireless connection into the private network is active, I am also able to connect using the public address of the Gateway machine. Watching the status of both NICs, the data is definitely transmitting over the cabled NIC.

I then disabled the wireless NIC, and the OPC connection over the public IP address continued to work... until I tried to add another item. It took at least 2 minutes for the add item box to appear, then it gave me an "RPC Server not available" error and didn't add the item. And all the while the original item I added was still working perfectly.

So, then I disabled the wireless NIC and killed the connection to the private network and tried to connect to the remote server using the public IP address.

Now the laptop gives me an "Unable to connect to the specified server" error.

Sir,

Your info tells me the 'managed' portion of your LAN is not allowing the traffic. Can you tell me more about what's bridging the networks?

jeparham said:

(I hope I have posted this in the correct area. If not, I suppose you can smack me in the head with a large trout.)

I have a PC running RSLinx Gateway. This PC is on my private "SCADA" network (192.168.1.x).

On any PC on the private LAN, I have no problem connecting to the remote OPC server and getting live data from the DH+ Network.

In the same building I have a "corporate" network that uses public IP addressing, and I need to get PCs on that network to connect to the remote OPC server as well. And that's where I run into problems. Simply put, the OPC client will not connect.
I've opened the appropriate ports in the hardware firewall isolating the private network. I verified my NAT settings in the firewall were correct. No connection.

I temporarily inserted an "Allow everybody and his brother to connect" entry into the firewall. No connection.

I set permissions and security in DCOM to let anyone connect. No connection.

I've tried multiple OPC test clients, which give me slightly differing errors:

"Connection to the server failed. ~RSLinx OPC Server ~"

"Runtime Error '-2147022986' The object exporter specified was not found."

Error: -2147022986, Method 'Connect' of 'IOPCAutoServer' failed.

And again, the test clients work as expected on the private network, the errors only happen when I try to connect from our WAN to the server.

Does anyone have any suggestions I might try to get this up and running?

Thanks,

jep

Click to expand...

Connect to "RSLinx Remote OPC server", not to "RSLinx OPC Server"

Is this right, you can see your opc remote server from rslinx lite but not from your test client?

if this is case, it may be your DCOM security settings, try this on the rslinx gateway, goto control panel -> Administrative tools -> component services -> my computer, right click properties,

select msdtc tab, click on Security Configuration button, next in security configuation, make sure Network DTC access is enabled and in Transaction Manager Communication, set No Authentication Required.

you need restart your computer for this to take effect.

johnyu said:

Is this right, you can see your opc remote server from rslinx lite but not from your test client?

if this is case, it may be your DCOM security settings, try this on the rslinx gateway, goto control panel -> Administrative tools -> component services -> my computer, right click properties,

select msdtc tab, click on Security Configuration button, next in security configuation, make sure Network DTC access is enabled and in Transaction Manager Communication, set No Authentication Required.

you need restart your computer for this to take effect.

<picture snipped>

Click to expand...

My server is a Windows 2000 machine, so the dialog boxes aren't the same as in XP.

So, I moved the RSLinx Gateway license from 192.168.1.105 to 192.168.1.101, which is an XP machine running RSView32 Works with RSLinx OEM. And as before, I can connect to the RSLinx Remote OPC server from any PC on the private LAN and browse the various nodes on the DH+.

I then configured MSDTC on the XP machine as shown in the example you provided, but I still cannot connect from any public IP address.

Once again I used the wireless NIC on my corporate laptop, configured as part of the private network (192.168.1.122), and it will connect to the remote server almost instantly on BOTH NICs. Disable the wireless NIC and the public address cannot connect any longer.

I've still got the firewall between the LAN and the WAN shut down.

I've verified the NAT is working correctly. I can ping the server from any WAN PC. I can map network drives on the server from any WAN PC.

But no matter what I try, I can not get this ^$&(*&#@ OPC client to connect.

jeparham said:

So, I moved the RSLinx Gateway license from 192.168.1.105 to 192.168.1.101, which is an XP machine running RSView32 Works with RSLinx OEM. And as before, I can connect to the RSLinx Remote OPC server from any PC on the private LAN and browse the various nodes on the DH+.

Once again I used the wireless NIC on my corporate laptop, configured as part of the private network (192.168.1.122), and it will connect to the remote server almost instantly on BOTH NICs. Disable the wireless NIC and the public address cannot connect any longer.

I've still got the firewall between the LAN and the WAN shut down.

I've verified the NAT is working correctly. I can ping the server from any WAN PC. I can map network drives on the server from any WAN PC.

Click to expand...

From your description, you seems only have 1 ip address (private LAN 192.168.1.105) for your gateway computer, your wireless address (192.168.1.122) is actually on the private lan not a public address.

I'm not exactly sure how your network is set up, usually to connect to both Public and Private network, you should have 2 network addresses (2 network cards), 1 configured for the private network (i.e. 192.168.1.105) and the other configured for the public network (eg. 10.0.1.12).

Also if you are using the firewall, you may also need to port forward all your Dcom ports to your rslinx gateway computer.

I had similar problems before. Assuming that the DCOM settings are correct, if you are trying to connect to a OPC server which is on a different workgroup than yours, try logging in with similar usernames and passwords as that of OPC server machine. It worked for me quite a few times. Can you also share the Dcom settings for OPCEnum and RSLinx. Windows gives a generic access denied or similar error code for connection problems. There are some users that you need to configure to make it work properly. The way I see it is that you are having some user credentials problem.