> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/products/cc-software/troubleshoot/command-centre-connection-issues/command-centre-connection-issues-opc-c.md). # OPC Connections 7.90 and higher - DCOM changes [Command Centre - Connection Issues](/knowledge-hub/products/cc-software/troubleshoot/command-centre-connection-issues.md) › OPC Connections 7.90 and higher - DCOM changes Often an OPC connection issue is **DCOM related** (this applies to both OPC DA and OPC AE). You can test using the Config client. From **v7.90** you need to change the registry to use **DCOM instead of WebSockets**. > ✅ **This is no longer needed from version v9.20 onwards.** Change the `ServerUrl` REG\_SZ at `HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\CARDAX\Command Centre FT\ServerUrl` from `wss://:8905` to `dcom://`. **This must be done on both the server and the workstation.** Follow the OPC Bridge Installation note for registering the DLLs on the server, firewall configuration, and DCOM access permissions. By default the login is username `opc` with **no password**. Check you can log into the Config client using these credentials. ## OPC credential lookup The server looks up the following values within the host machine's registry: | | Path / value | | --------------- | ------------------------------------------------------------------ | | **(32-bit OS)** | `HKEY_LOCAL_MACHINE\SOFTWARE\Cardax\Command Centre FT` | | **(64-bit OS)** | `HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Cardax\Command Centre FT` | | Username value | `OPCUserName` (REG\_SZ) | | Password value | `OPCPassword` (REG\_SZ) | > **Note:** For all logon scenarios, the corresponding operator (with matching username/password) must first have been created, configured, and enabled as an operator in Gallagher Command Centre. To **disable** the automatic logon feature for the OPC server, ensure there is no default OPC operator configured with the credentials above. The default OPC logon with a blank password is intended **for testing purposes only; use on production sites is strongly discouraged.** Check whether the Command Centre server and OPC DA client are on the same domain, or are workgroup PCs. ## Connection strings The CLSID at the end (in `{}`) is required when connecting from a remote PC (it will not hurt on the local PC either): ``` opcda:///CCFTOPCData.CardaxOPCDataServer opcda:///CCFTOPCData.CardaxOPCDataServer/{751ff1af-4a4c-47d6-bf82-7ff008890c70} ``` Replace `` with the host name of the FT Server PC. You can also use the IP address, or `localhost` if you are on the same PC as the FT server, for example `opcda://localhost/CCFTOPCData.CardaxOPCDataServer`. ## Re-enabling OPC after upgrading to v8.00–8.20 Upgrading to v7.90 (and particularly v8.XX) disables DCOM on the server, which also disables OPC. 1. Change the `ServerUrl` registry key from `wss://servername:8905` to `dcom://servername`, then restart the Command Centre Services. 2. On every workstation in use, edit `C:\Program Files (x86)\Gallagher\Command Centre\ConfigClient\CCFT.exe.config` and change `wss://servername:8905` to `dcom://servername`. 3. Obtain `FT DCom Setup.exe` from an older version of Command Centre and run it in the Bin folder with **Legacy DCOM Settings**. Contact Technical Support for a link. > **Important:** If the FT DCOM Setup tool is run, the computer it is run on must be restarted for the changes to take full effect. This reverts DCOM to active for workstations and re-enables OPC alarms and events. If the OPC connection is on the server, step 1 (registry change) is needed; after restarting the services and establishing the OPC connection, the settings can be reverted back to `wss://servername:8905`. ## Re-enabling OPC after upgrading to v8.30+ From **vEL8.30.xxx** onwards, after changing the `ServerURL` registry from `wss:` to `dcom:`, take these two steps: 1. On every workstation, change the relevant line in `C:\Program Files (x86)\Gallagher\Command Centre\ConfigClient\CCFT.exe.config` from `wss:` to `dcom:`, for example: ```xml ``` becomes ```xml ``` 2. On every workstation, run a Command Prompt as Administrator from `C:\Program Files (x86)\Gallagher\Command Centre\ConfigClient\` and type: ``` Regsvr32 CCFT.exe ``` *** 🔗 **Related** * [Unable to log into Configuration Client](/knowledge-hub/products/cc-software/troubleshoot/command-centre-connection-issues/command-centre-connection-issues-u-3.md). The DCOM logon fix. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation by asking a question. Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters: ``` GET https://help.security.gallagher.com/knowledge-hub/products/cc-software/troubleshoot/command-centre-connection-issues/command-centre-connection-issues-opc-c.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. 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