Connecting RFEM

RFEM 6 runs on your machine. Dlubal CALC runs in your browser. Joining the two is a small helper program called the Dlubal-Connector, which listens on localhost:8083 and passes instructions to RFEM.

Once it is running and paired, you can work like this:

Build a portal frame, span 12 m, height 5 m, HEA 240 columns and an IPE 400 rafter,
in a new RFEM model. Then calculate it and give me the support reactions.

Dlubal CALC builds the model in your open RFEM, runs the analysis, and reads the results back. You watch it happen in RFEM while it does.

RFEM access is included in every plan, Free included. If an answer tells you that RFEM is a paid upgrade, that is the model guessing, not a real restriction. What the shipped configuration grants is listed in Plans and credits.

Requirement

RFEM 6 on the same machine as the Dlubal-Connector, and a Dlubal API key in your Dlubal CALC settings. RFEM access itself is on every plan, so there is nothing to buy first.

Setting it up

Install the Dlubal-Connector on the machine where RFEM 6 is installed.
Open Dlubal CALC and click the RFEM icon in the message bar, below the input field. That icon carries the live status and the action for whatever state you are in. Until you have paired once, the RFEM card in the sidebar shows the same thing.
Pair the connector once. Pairing ties this connector to your account, so a connector on your machine cannot be driven by anybody else. Windows asks you to confirm it, once.
Open RFEM 6.

The order of steps 3 and 4 does not matter. The order of steps 1 and 3 does: the connector has to be running before Dlubal CALC can pair with it.

If Windows blocks the installation

The Dlubal Connector is currently not digitally signed. Windows therefore does not recognise the publisher, and depending on your settings one of two things happens.

SmartScreen says "Windows protected your PC" and names an unknown publisher. More info and then Run anyway gets you past it.

Smart App Control blocks outright, and there is no button that lets you allow this one file. It is only active on Windows 11 machines that were set up from scratch.

Important

Do not turn Smart App Control off in order to install the connector. Windows only lets you change this setting in one direction: once it is off, you cannot switch it back on without reinstalling the operating system. Please get in touch with us instead, so we know how often this happens.

The same menu carries a "How to connect RFEM" entry, which opens the official walkthrough: Connecting Dlubal CALC and RFEM 6. The chat offers that link too, whenever it has no RFEM tools and you ask for something that needs them.

When the chain is complete, the connection status in Settings reads like this:

Dlubal-ConnectorConnected

RFEM 6Connected

MCPReady

The one confusion worth understanding

Important

The green dot next to RFEM means the connector answered. It does not mean RFEM is connected.

That single distinction explains most of the trouble reports in this area. The connector is a separate program with its own lifetime. It keeps running after you close RFEM, and it answers Dlubal CALC perfectly well while RFEM is not there at all.

Example: RFEM is open, the dot next to "RFEM" in the sidebar is green, and the answer still says it has no access to RFEM. Cause: The connector is answering, but the chain behind it is not complete. The dot only reports the first link. Check: Open http://localhost:8083/rfem-info in your browser. If you get {"rfem_version":"","rfem_license":""}, RFEM has never reported itself to the connector. Do not use /health for this: it returns 200 with an empty body and says nothing about RFEM.

Which version is actually running

The connector installs a Python component into RFEM's own Python, and then starts it. Those are two separate things, and they can disagree. If a component from an earlier session is still running when the connector starts, the connector adopts it instead of starting a new one, so a freshly installed version can sit on disk while the old one keeps serving.

Settings → MCP servers shows both facts on one line under the connection status, for example Dlubal-Connector 2.28.8 · MCP 1.0.11. The second number is the one that is running.

When the two disagree the number turns amber, and the same warning appears next to the RFEM icon in the message bar. You do not have to do anything about it: the connector restarts the component onto the installed version by itself, usually within a couple of minutes, and the warning clears when it has.

Example: An answer tells you a capability "is not available in your RFEM version", next to a green dot. Cause: Usually an outdated component rather than anything to do with RFEM. It never offered the tool the answer tried to use, so the model explained the gap by guessing. Check: Settings → MCP servers. If the MCP version is amber, give it a few minutes. If it stays amber, restart the connector.

What the connector reports as blocked

Every state below has its own section in RFEM troubleshooting, and Dlubal CALC links straight to the one that applies when it knows which it is.

From version 2.26.0 the connector names the dominant reason the chain is unusable, instead of reporting a bare failure. These are the values it reports and what each one means for you:

Reported blocker	What it means	What to do
`rfem_not_installed`	No RFEM 6 installation found on this machine	Install RFEM 6, or pair the connector on the machine that has it
`mcp_installing`	First-time setup is installing its Python component, which takes minutes	Wait. It resolves by itself
`rfem_not_running`	`RFEM6.exe` is not running	Open RFEM 6
`rfem_modal_dialog`	A modal dialog is open in RFEM and blocks its interface	Click the dialog away in RFEM
`mcp_unresponsive`	The component accepts connections but stopped answering	Restart the connector
`api_key_missing`	No Dlubal API key available, so the component was never started	Enter your Dlubal API key in Dlubal CALC settings
`mcp_starting`	A start or restart is in flight	Wait, this phase is bounded
`mcp_down`	RFEM runs, but nothing is serving the connection	Restart the connector
`grpc_unreachable`	The component is up, but RFEM is not listening on its interface port	Restart RFEM
`not_proven`	Everything is up, but nothing has demonstrably run yet	Send one request, this is a warm-up state

Warning

rfem_modal_dialog is worth singling out. An open dialog in RFEM, even a harmless one asking you to confirm something, stops RFEM from answering. The model looks broken and the cause is a window waiting for a click.

When the browser is the one blocking

Chrome 142 and later ask for permission before a page on calc.dlubal.com may talk to localhost. If that permission is denied, the connector looks unreachable and nothing is actually wrong with it.

Example: The connector is running, http://localhost:8083/rfem-info answers when you open it directly in a tab, but Dlubal CALC still reports it as not reachable. Cause: Chrome is blocking calc.dlubal.com from reaching http://localhost:8083. This is a browser permission, not a missing connector. Check: Allow "Local network access" for calc.dlubal.com in the site settings, then reload.

When "not reachable" really means "not paired"

A connector that is running but not paired to your account refuses the request. Depending on where that refusal surfaces, it can read as "not reachable" rather than "not paired", which sends you looking for a network problem that does not exist.

If the connector answers http://localhost:8083/version in a browser tab but Dlubal CALC insists it cannot be reached, pair it again before you touch anything else.