Remote Control

Remote control protocol

The standalone model driver may be controlled from a remote host over TCP/IP. The driver listens for connections on TCP port 25200, and accepts commands using a simple text-based protocol.

Commands are plaintext strings, terminated by a newline (ASCII LF (0x0A), '\n' in C).

Command responses

After the command has completed, the driver will respond with a line containing a single period (".\n"). If there was an error, it will respond with a question mark ("?\n").

Lines beginning with a '-' contain error messages in response to the currently executing command. Lines beginning with a '+' contain a normal (non-error) response.

Lines beginning with an exclamation point ("!...") indicate an asynchronous message from the driver to the controlling host. The driver may produce asynchronous notifications at any time. Notifications include:

!ok

Indicates that the connection has been established.

!running

Indicates that the simulation is running.

!paused

Indicates that the simulation is paused.

!standby

Indicates that the simulation is in standby mode (trimming, playback, or other long-running process).

!crashed

Indicates that the driver has encountered an error.

!reset

Sent when the simulation is reset

!done

Sent when the simulation is shutting down

Other asynchronous notifications may also be sent, described elsewhere.

Datagram sockets

Commands may also be sent on UDP port 25200. The driver does not send a response to commands received over UDP, so commands like model.get are not useful in this mode, but for cases where the host does not need a reply using UDP is often simpler.

Tips

You can communicate with the driver directly with the Unix shell command:

telnet localhost 25200

Or from a different machine, substitute 'localhost' with the name of the host on which the driver is running.

Available commands

The following commands are available:

run

Start running

pause

Pause the simulation

runtoggle

Toggle between 'running' and 'paused' states.

reset

Reset the simulation (e.g., after a crash) to the last checkpoint.
The simulation is left in the 'paused' state afterwards.

shutdown

Stop the simulation and terminate the driver.

model.set varname value

Sets the value of a Scope model variable. varname must be the full path to the variable (not including the WORLD group), and all upper-case.

model.get varname

Returns the value of a Scope model variable.

model.lsfields

Returns a list of all Scope model variables in the current model, one per line (internal use).

model.update

Update all model outputs (internal use)

model.step

Single-step the model

model.reload

Reloads the model in its initial configuration.

model.save filename

Saves the current state of the model to the named checkpoint file. If the filename is omitted, a default checkpoint file is used. Subsequent 'reset' operations will restore this state.

model.restore filename

Restores the named checkpoint. If the filename is omitted, the most recently saved checkpoint is restored.

model.trim

Initiate the trim process. See for details.

Trimming the model

The model.trim remote control command initiates the trim process. This will try to find a set of control positions which will hold the aircraft at a given flight path.

By default, the aircraft is trimmed to level flight at the current airspeed. Additional arguments to model.trim may be supplied as follows:

model.trim speed climbrate turnrate

speed

Specifies the in-plane inertial velocity in feet/sec. If omitted, defaults to the current inertial velocity

climbrate

Specifies the climb rate (if positive) or descent rate (if negative) in feet per second. Defaults to 0.

turnrate

Specifies the turn rate in radians per second. Defaults to 0.

The trim process may take up to 10 seconds. The status of the trim is reported via the following asynchronous notifications:

!trim started

Sent when the trim process starts

!trim finished

Sent when the trim process completes successfully

!trim failed

Sent if the trim process fails