What is SimConnect in Prepar3D, and how do I set it up?

SimConnect is Prepar3D’s application programming interface for exchanging simulator data and commands with add-ons and external programs. For a local add-on, it is normally installed with Prepar3D and needs no manual configuration. Install the add-on, load a flight and run it; networked clients require matching server and client settings plus firewall access.

What does SimConnect do in Prepar3D?

SimConnect gives other software a controlled way to communicate with Prepar3D. An application can read aircraft position and simulator variables, subscribe to events, send commands, work with AI aircraft and exchange custom data.

It is the connection layer used by many moving maps, flight trackers, hardware interfaces, instructor stations and companion applications. SimConnect is not a separate control panel that must be opened before every flight, and it is not the same thing as the optional Prepar3D Software Development Kit.

Do I need to install SimConnect separately?

Most Prepar3D users do not need to install SimConnect separately because the simulator includes its own runtime. Our explanation of the bundled SimConnect component also shows why installing an add-on is normally enough for local use.

Legacy SimConnect interfaces can coexist side by side. Installing only the newest component does not necessarily satisfy software compiled against an older interface. Use the official redistributable supplied with Prepar3D or the add-on installer rather than copying a downloaded SimConnect.dll into Windows system folders.

Bitness is another source of confusion. An external 32-bit application may connect to a 64-bit Prepar3D installation if it has the appropriate client components, while an in-process module loaded directly by the simulator must match the simulator’s architecture.

How do I set up SimConnect for a local add-on?

For a local application running on the Prepar3D computer, the default SimConnect connection normally works without an XML or CFG file.

1. Confirm compatibility. Install the add-on build intended for your Prepar3D generation. Prepar3D compatibility stated without a supported release or architecture is not always enough.
2. Run the proper installer. Allow it to install the required SimConnect and Microsoft runtime dependencies. Avoid moving installed DLL files by hand.
3. Start Prepar3D. Load fully into a flight rather than leaving the simulator at its opening screen. Some clients cannot complete their connection until the aircraft and simulation session exist.
4. Launch the client application. Unless its instructions say otherwise, run it after the flight has loaded. If Prepar3D is elevated with administrator rights, the client may need the same privilege level; we recommend running both normally where possible.
5. Check the application’s status. Look for a connected indication or changing simulator data. There is usually no separate SimConnect switch inside Prepar3D.

If the add-on supplies its own connector, configuration utility or SimConnect.cfg, keep that arrangement. Replacing an application-specific configuration with a generic one is a common cause of failed connections.

How do I configure SimConnect over a network?

A remote SimConnect client needs a server definition on the Prepar3D computer and matching connection details on the client computer.

1. Give the Prepar3D computer a stable LAN address. A router reservation is preferable to an address that changes after every restart.
2. Configure the SimConnect server. Create or edit SimConnect.xml in the running Prepar3D version’s roaming application-data folder. Define an IPv4 connection that listens on the simulator computer’s LAN interface and uses an unused port. Preserve any entries installed by other add-ons.
3. Configure the remote client. Place SimConnect.cfg where that application expects it, commonly beside its executable or in a user documents location. Its protocol, server address and port must correspond to the server entry. The address is the Prepar3D computer’s LAN address, not 127.0.0.1.
4. Allow the connection through Windows Firewall. Permit Prepar3D or the selected port on the private network. Do not expose or forward a SimConnect port to the public internet.
5. Load a flight before starting the client. This removes the opening-screen state as a possible cause while testing.

Some applications provide host and port boxes or install a bridge service, making a manually created SimConnect.cfg unnecessary. Follow the application’s method rather than combining two configurations.

Why won’t SimConnect connect to Prepar3D?

Most SimConnect failures come from a missing legacy runtime, the wrong Prepar3D profile, mismatched privileges or incorrect network details.

• The add-on never connects locally: verify that it supports the installed Prepar3D release, then reinstall it so its dependencies are registered correctly.
• The program reports a missing assembly or side-by-side error: install the legacy SimConnect redistributable specified by the add-on. Reinstalling the newest runtime alone may not fix it.
• It connects only when both programs run as administrator: remove unnecessary elevation from Prepar3D and the client, or keep their privilege levels matched.
• A remote client times out: check the server IP address, port, Windows network profile and firewall. Test on the same private LAN before adding VPNs or extra network adapters.
• The files appear correct but are ignored: make sure you edited the profile belonging to the Prepar3D version actually running. Also check that Windows has not saved the file as SimConnect.xml.txt or SimConnect.cfg.txt.
• Data remains blank at the menu: load into an aircraft and wait until the flight is fully active.

For connector applications, our loaded-flight, permissions and firewall troubleshooting checks cover the same failure pattern without duplicating an application’s own installation instructions.

Do developers need the Prepar3D SDK?

Only developers building or debugging SimConnect applications need the Prepar3D SDK. Install the SDK corresponding to the Prepar3D release you intend to target, then compile against its documented headers, libraries or managed assemblies rather than an unrelated copy found in another add-on.

A practical way to understand requests, events and AI control is our worked SimConnect example using waypoint streaming and a second aircraft. Older examples remain useful for the basic model, but every interface used should still be checked against the SDK for the target Prepar3D version.