Plugin for X-Plane flight simulator which allows reading and writing simulation properties
C++ Shell QMake Other
Latest commit 81adc00 Mar 7, 2018
Ville Ranki
Ville Ranki mxe tuning



A plugin for X-Plane and other simulators that allows commanding the simulation from external programs through an easy-to-use TCP protocol.

Supported simulators

  • X-Plane 9, 10 & 11 - native support. X-Plane 11 currently only tested.
  • FlightGear - basic support via Transformer (see later)


  • Multiple concurrent connections
  • Set and get datarefs
  • Support for different dataref types: int, float, double, int[], float[], data
  • Simulate key and button presses
  • Execute commands
  • Free & open source under GPLv3
  • Client libraries available for Qt (c++), Java and C#

Known users:


ExtPlane-Transformer is an application that works as ExtPlane server and can transform output from ANY simulator to ExtPlane protocol. Work on Transformer is only beginning but expect to see support for more simulators in near future.


  • GNU GPLv3

Articles and guides


Ext-Plane Plugin + Panel

Ext-Plane Plugin


ExtPlane uses the Qt Framework for cross-platform compatibility. Before building you'll need to setup Qt 5 or greater to compile. You'll also need to check out the X-Plane SDK ( to the directory next to the ExtPlane directory. The X-Plane SDK can be either at ~/SDK or ../SDK or ../XPlaneSDK relative to the ExtPlane directory.

The requirements for ExtPlane are as follows:

  • C++ Toolchain
  • Qt Framework 5+
  • X-Plane SDK 3.0+

Debian/Ubuntu Linux

# 1: Install required libraries and tools
sudo apt install git build-essential qt5-qmake qt5-default qtbase5-dev

# 2: Download X-Plane SDK and ExtPlane source code from GitHub
git clone
git clone

# 3: Build project
cd ExtPlane


# 1: Install required libraries and tools
# Download and install X-Code and Developer Tools from
# Download and install Qt5 from

# 2: Download source code from GitHub
git clone
git clone

# 3: Build project
cd ExtPlane

# Note: If qmake is not on your command path, add the Qt bin directory to your path using
# export.


# 1: Install required libraries and tools
# Download and install Qt5 from
# Download and install Git from

# 2: Download source code from GitHub
git clone
git clone

# 3: Build project
cd ExtPlane

# Note: If you do not have a C++ compiler, you can install one of the following:
# MinGW version of Qt:
# Windows 7 SDK:
# Windows 8 SDK:
# Visual Studio Express:

After the build

A fat plugin will be in extplane-plugin/extplane. It will contain platform specific plugins you have built. For example after building linux & windows plugins it should look like this:

└── 64
    ├── lin.xpl
    └── win.xpl

You can copy the whole directory to XPlane's plugin directory:

cp -R extplane-plugin/extplane /path/to/xplane/Resources/plugins

Cross-compile to Windows from Linux

This is possible using mxe cross-compilation tool. See file scripts/ for instructions.

Test Session

Launch X-Plane in console and observe the output. You should see something like: ExtPlane-Plugin: Listening on port 51000. All console output from Ext-Plane will start with ExtPlane-Plugin. Open another console and run telnet localhost 51000. Wait until you see line EXTPLANE 1. Then try typing the following commands:

sub sim/cockpit/electrical/night_vision_on
set sim/cockpit/electrical/night_vision_on 1
set sim/cockpit/electrical/night_vision_on 0
sub sim/flightmodel/position/local_y 100
set sim/flightmodel/position/local_y 3000
key 0
key 0
set sim/flightmodel/engine/ENGN_thro [1,0]
set sim/flightmodel/engine/ENGN_thro [0,0]
get sim/aircraft/engine/acf_num_engines

Protocol Input

The protocol uses a simple TCP socket connection to port 51000. Commands and replies are sent as text strings as defined below.


  • sub {dataref} [accuracy] Subscribe to dataref, with optional accuracy.
  • unsub {dataref} Unsubscribe dataref.
  • set {dataref} {value} Set dataref to value. Dataref must be subscribed first.

With accuracy you can decide how much the dataref's value can change before a update is sent. Set it to as large value as possible to maximize frame rate and minimize network traffic. For data datarefs, the accuracy represents the update interval in milliseconds.

List of datarefs can be found at:

For example, to subscribe to the indicated heading with an accuracy of 10 degrees, send

sub sim/flightmodel/misc/h_ind 10.0

If you want to set a dataref which supports writing, you can send the following:

set sim/flightmodel/misc/h_ind 267.32

Array datarefs can be set the same way. You can give less values than the dataref holds. For example this sets full throttle for engines 1 & 2:

set sim/flightmodel/engine/ENGN_thro [1,1]

Keys and Buttons

  • key {key id} Create a command key press.
  • but {button id} Press down an button.
  • rel {button id} Release button pressed using "but" command.

List of key and button id's can be found at: Note that the key and button id's are numbers, not names. X-Plane does not provide a way to lookup keys or buttons by name.


  • ** cmd once {command} ** Execute command. It begins and ends immediately.
  • ** cmd begin {command} ** Begin execution of command. Then it will be "held down".
  • ** cmd end {command} ** Stop execution of command, that was started before.

Command identifiers are strings that look like datarefs.


  • disconnect Disconnect the TCP socket.
  • extplane-set {setting} {value} Set ExtPlane setting

Supported settings are:

  • update_interval {value} How often ExtPlane should update its data from X-Plane, in seconds. Use as high value as possible here for best performance. For example 0.16 would mean 60Hz, 0.33 = 30Hz, 0.1 = 10Hz etc.. Must be a positive float. Default is 0.33.

Protocol Output

  • EXTPLANE {version} Sent when connected. Version number is currently 1.
  • u{type} {dataref} {value} Dataref has changed in value based on accuracy.
    • Types may be i (int), f (float), d (double), ia (int array), fa (float array), or b (data).

Int/Float/Double Datarefs

Example output:

ui sim/aircraft/engine/acf_num_engines 2
uf sim/cockpit2/gauges/indicators/slip_deg -0.023
ud sim/flightmodel/misc/h_ind 267.32

Int/Float Array Datarefs

Example output (a float array, size 4):

ufa sim/flightmodel/position/q [0.84599,-0.00730657,0.00933933,0.533067]
uia sim/cockpit2/engine/indicators/N1_percent [99,97]

Data Datarefs

Data datarefs output data in base64:

ub sim/aircraft/view/acf_descrip RXh0UGxhbmUgU2ltdWxhdGVkIENvbm5lY3Rpb24=

Console Output

ExtPlane plugin outputs some log to stdout, so if you have problems with the plugin, start X-Plane in console and look for any output starting with ExtPlane-Plugin.

Custom Datarefs

ExtPlane can provide custom datarefs which simplify some common tasks or create a wrapper for X-Plane SDK API calls which cannot be accessed through datarefs.

  • extplane/navdata/20km
    • Provides a list of nav aids within a 20km range of the aircraft's position.
    • When this dataref is first accessed, ExtPlane will create a spatial database of all registered nav aids by using the XPLM NavAid APIs (~400ms). This then allows for a performant (<2ms) dataref which can list nav aids on the fly.
    • Each nav aid is returned on a single line in format of: ID:TYPE:LAT:LON:LOCALX:LOCALZ:HEIGHT:FREQ:HEAD:NAME.
    • For example, the nav aid for KSEA might look like this: KSEA:1:47.4475:-122.308:14461.6:-211.06:131.978:0:0:Seattle Tacoma Intl
  • extplane/navdata/100km
    • Provides a list of nav aids within a 100km range of the aircraft's position.
  • extplane/atc/124thatc/latest
    • Provides the latest ATC communication as a string from the 124th ATC plugin.

Client Libraries

Client libraries can be found in the client directory. Currently only a Qt client library is provided. Creating a client for ExtPlane is pretty easy. If you create one, please add it to the client directory.

Coding Guidelines


Always group headers in a meaningful format (ie all Qt headers should be grouped together, and all ExtPlane headers grouped together). In addition, make sure that headers are always fully relative (ie use ../util/header.h instead of util/header.h). This is required to build across all platforms.

Platform-Dependent Code

When writing code which uses new features currently not implemented, always make sure to first try to use Qt cross-platform classes and libraries. When using platform dependent code, make sure to #ifdef the sections of code which will only work on a specific platform. You can use standard Qt defines, or additional defines such as TERMIOS_AVAIALABLE to help with this.

Creating new data sources to support simulators

Look at class DataSource. You'll need to subclass it and implement any virtual functions missing. The functions are documented in the source. You'll need to do a conversion between X-Plane dataref and the simulator's own value presentations. Usually they area easy to do but complex stuff such as navigation may be impossible to do with common API.

When you have an implementation of a DataSource, add it to ExtPlaneTransformer class implementation. Then it should be available in the GUI.

To create a custom GUI for the source, create a QML file named datasources/DataSource[sourcename].qml. This is not mandatory.

See the existing datasources for examples. Thanks for contributing and make a github pull request when you're ready.

Contact / Feedback

Original Author:


Use GitHub's issue tracker to report bugs or feature requests.

Contributions welcome!