DSEL/USEL - Stream Data Output

DSEL Request

X-Plane Settings “Data Output” screen lists a hundred or so data sets which can be output to the Cockpit, saved to file, or sent via UDP. The DSEL command allows you to effectively request one (or more) of these data set to the configured port.

This might save you from manually navigating to Settings in-game and selecting the dataset and setting the networking details.

Send

The “index” requested matches the index lists on the Data Output window, so:

index = 1
msg = struct.pack('<4sxi', b'DSEL',
                  index)               # requesting index==1, first item in the list
sock.sendto(msg, (beacon['ip'], beacon['port']))

Index	Dataset
0	Frame rate
1	Times
…
138	Servo aileron/elevator/rudders

You can request more than one index at a time within the same command, by packing more integers, e.g.,:

items = [0, 1, 138]
msg = struct.pack('<4sx{COUNT}i'.format(COUNT=len(items)), b'DSEL', *items)

To stop receiving data, use send USEL command with the same list of integers.

Note

DSEL merely indicates what data to send, not where to send it. It will not automatically send the requested UDP data to the same port making the request (unlike other commands listed here.)

Therefore, you’ll need to also set the Internet options using ISE4 or ISE6.

DATA Response

The result of the DSEL command will be a simple data structure sent to the IP / Port set by ISE4 or ISE6. (Let me say that again – the data is sent to the set 1 IP / Port, not returned to the same port which made the DSEL request.)

Receive

The received packet will start with DATA, followed by 9 floats.:

header, index, *vals = struct.unpack('<4xf8f', data)
assert header == 'DATA'

index is a float, but represents the (integer) index you requested with DSEL. That way you know which dataset the data values correspond to.

The values will always be 8 floats (in the above example, we’ve unpacked them into a list vals. What are they? There is no way of determining programmatically. But, they will match the 8 values (8 slots, really) displayed if you were to select “Show in Cockpit” for that dataset.

For example, index 0 is listed as “Frame rate”. If you were to Show in Cockpit, you’d see

f-ac	f-sim		frame	cpu	gpu	grnd	flit
vals[0]	vals[1]	vals[2]	vals[3]	vals[4]	vals[5]	vals[6]	vals[7]
/sec	/sec		time	time	time	ratio	ratio

The eight values represent the above 8 slots (you’ll note the third slot is blank, and the third data item is ‘-999.0’)

---

1

Of course, the set port might be the same port as your socket, but you’d have to configure it that way, either using ISE4 or ISE6 or simply setting the IP/Port on the X-Plane Settings->Data Output page: Select “Send network data output” and set the values for IP Address and Port to match your socket’s address and port.

>>> cmd = 64
>>> ip = sock.getsockname()[0]
>>> port = str(sock.getsockname()[1])
>>> msg = struct.pack('<ISE4xi16s8si', cmd, ip.encode('utf-8'), port.encode('utf-8'), 1)
>>> sock.sendto(msg, (beacon['ip'], beacon['port']))
>>>