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0 votes
asked by (44 points)
Ive done my best to work this out myself, but finally concluded I need help :)

I have a 3-screen Mac system - XP11 is amazing and works extremely well on screens #1, 2 & 3.

Now, I want to display instruments by themselves on screen #4.

I understand that you need separate instances of XP11 to do this ... XP11 runs one view per instance, so in order to have multiple views, you need multiple instances - that makes sense.

I can get this working by running separate instances of XP11 on separate Macs, and networking them together - it's easy to set up because each machine has a separate IP address. All good so far -> but I want to achieve this on one machine.

The XP11 Forum contains posts by Windows users who also want to run instruments on a separate display. They run multiple instances of XP on one machine, with one instance as a 'master', and the other as an external independent view.

The trick seems to relate to setting up the IP addresses and UDP ports. Unfortunately, the instructions posted in the forum were for XP9, and the settings screens on XP11 are quite different, so I couldn't figure it out.

I can easily run multiple instances of XP11 on one Mac - I can fly an F4 Phantom II on screen #1, a Stinson L5 on screen #2 and a Cirrus SF50 on #3 - or all 3 instances on one screen (albeit a bit noisy - it would be good if the sound muted when the window was deactivated), with hardly any degradation in frame rate.

So the question is ...

Given that each instance of XP11 is running on a single Mac with a single IP address, how can I set up the UDP ports (assuming this is what I need to do ) on one instance to run as a 'master' (eg cockpit view with HUD) and others as independent external views (eg instruments / external views) ???

Many thanks,


3 Answers

0 votes
answered by (44 points)
edited by

OK - I worked it out - it's actually REALLY easy.

You need to run 1 instance of XP11 to generate the simulation (the MASTER), and one instance to generate each external view (the Slave/s).

A. Set up the FIRST instance of XP11 as MASTER

     1. Launch XP11

     2. In Settings/Network, set 'This machine's role' = Master


          - enter the SAME IP address as the Master (THIS MACHINE'S IP ADDRESS)

          - set the UDP port to 49020

     4. Leave the UDP ports at the default values :-

          Port we receive on = 49000

          Port we send from = 49001

     5. Click DONE

     6. Start your flight, then PAUSE 

B. Set up the SECOND instance of XP11 as SLAVE

     1. Launch the second instance of XP11

          open terminal and type "open -n -a [pathname]", where [pathname] is the path for your XP11 app.

          It's actually easier to type "open -n -a ", then drag the X11 app onto the end of the text.

     2. When the app launches, immediately click the 'Settings' button and go to Networks.

     3. In Settings/Network, set 'This machine's role' = External Visuals

     4. For MASTER MACHINE, set the IP address to the same as the Master (THIS MACHINE'S IP ADDRESS)

          Leave the UDP port at 49000

     5. Set the UDP ports :-

          Port we receive on = 49020

          Port we send from = 49021

     6. Click DONE

     7. Click Resume Last Flight or New Flight - the MASTER will automatically set the aircraft and airport.

C. You will see the 2nd instance of XP11 is PAUSED, and the aircraft and airport are the same as the MASTER.

D. Set whichever views you like, then un-pause - and fly !




1. You can run as many instances of XP11 as you like - one for each view.

2. I had 3 instances running with different simulations - with virtually no degradation in frame rate.

3. You can use this little AppleScript to launch 1 instance of XP11 :-

     do shell script "open -n -a [pathname]

     A trick - if any segment of your pathname includes a space, then enclose in single quotes ... like this ...

     do shell script "open -n -a /Applications/'X-Plane 11'/"

     You can use this as many times as you like - just run it once for each instance.

5. Once you've tested the script, save it as an 'Application' - then just double-click to launch a new instance of XP11.



commented by (44 points)

Hi ...

This procedure describes how to run multiple instances of X-Plane on Mac OS. In Mac OS, you can't normally run multiple instances of the same app, like you can in Windows.

The 'open -n -a' terminal command is to launch additional instances of X-Plane.

[-n] tells Mac OS to pen a new instance of the application, even if one is already running.

[-a application] specifies the application to use - in this case, 'X-Plane 11'

If you're using Windows, you don't need to do this because Win can run multiple instances of X-Plane without the need for a terminal command.

I hope that helps :)


commented by (10 points)
Thank you for the explanation.  This method did work for me after trying it a second time.  Appreciate the original post!
commented by (17 points)

Hi Robert,

Did you manage to write a hardware-level driver to interface the Elite controls. If so I'll be very interested in it.

Since I saw this for Xplane 11 I thought it might be possible: If you have flight instruments or other hardware you plug into a serial port, you can send datarefs from X‑Plane to the serial port to drive them. To do this, first go to the Data Output section of Settings and click on Dataref Read/Write. Check the box next to A COM port, then select the com-port number and enter the baud rate in the lower-right.

Best regards, Caesar

commented by (22 points)
Hi Caesar:

Unfortunately no, and I did not even try.  It's a complex job requiring expertise in very low-level programming.  I have not done that since 1976, more than forty years ago…  Plus I have no detailed documentation about the Elite hardware.

It would be much simpler to connect the Elite hardware with a few levers and linkages to Saitek hardware (or joysticks) and I have actually thought about looking into that. Easier to debug too!  :-)
commented by (17 points)
I'll keep the Elite hardware running with FSX and I'll use X-Plane 11 with a joystick then, I wished I could switch completely to X-Plane. Anyhow, thanks for the input!

0 votes
answered by (5.3k points)

Hi Garry and Robert,

Why don't you have a look at Panel Builder which can be found at   in the USA or   in the UK instead of trying to run additional copies of X-Plane.



commented by (44 points)
Hi Glenn,

Many thanks for that suggestion ...

Yes, I've looked at SimPlugIns - they look great, but are for PCs, not Macs {:/

Multiple views is also very useful for displaying maps, and keeping an eye on the surrounding terrain - its actually really easy to do - and free !
commented by (5.3k points)
Hi Gary,

Thought this may help.  Good luck in solving the dilemma.

PS.  Seems as though we both live downunder.  Temps for us have been high 30s with anticipated temps in the mid 40s for the next few days (or weeks).

0 votes
answered by (22 points)
Do you know how the computational load is distributed over the CPU and GPU?

Presumably the CPU is tasked with simulating the plane's behaviour and the GPU with painting the scenery.

And presumably the master instance simulates the plane while the other instances only paint additional views.

If that is true, then I need a powerful machine for the master instance but only moderate machines for the other instances although they need a good graphics card.
commented by (44 points)

Hi Robert

Today we are 47*C apart :)

Based on my understanding of your 6-screen setup, IMHO you don't actually need to run multiple instances or use multiple machines ... if all you want to do is display different perspectives of the same view, then XP11 can do that for you with only 1 instance.

I suggest you look at XP11's multi-monitor modes in Settings/Graphics ... this allows you to set each of your monitors to display a different perspective of the same view.

For example, you could set the 2 left monitors to look out the left window and over the left wing, the front 2 monitors to look out the left/right front screens, and the 2 right monitors to look out the right window and over the right wing - all within one instance of the app.

Here's what I mean - sorry for the poor pic, it only took a minute to set this up for you, I haven't adjusted the offsets etc to compensate for the bezel width.

Contrast this with a SINGLE perspective stretched across 3 monitors - it looks flat, and (as you mentioned) the perspective is all wrong - although it does give a good effect with very little effort and no setup.

I suggest you set up XP11 with several monitors attached, and experiment with the settings in Settings/Graphics - you will see one setup panel there for each monitor connected.

This method requires only one instance to run the simulation, which reduces the load on your processor, and generate one view for each screen - XP11 will do all that for you.

I hope that helps ...


commented by (22 points)

Hi Gary,

Temp. has gone up here to -1.5; view from the kitchen window:

(the mountains in the background are the Jura, as in Jurassic).

However, when I try to follow your suggestion I get: 

monitor panel

i.e. I seem to be able to do something with the second monitor OR with the main one, but not both…  But this is perhaps because the lid of my MacBook is closed, as it sits behind what I think of as my "main monitor".  There is a Cinema (2560x1600) attached and an Acer (1920x1080).  So I'll experiment some more.

However, your answer indicates once again that we —and X-Plane— urgently need a terminology to describe these issues in unambiguous terms.

I'm off to a meeting, let you know as soon as I can.


commented by (44 points)
Hi Robert,

Thanks for the pic - very beautiful view, we could do with a bit of snow here now, its 9pm and still 24*C after a very hot day.

Looking at your screen ... your Mac has definitely 'seen' at least 2 monitors - that's why you have 2 settings panels (and there may be a 3rd off to the right).

Interestingly, the size of the monitor settings panels in Settings/Graphics is in proportion to monitor resolutions - so it looks like your 'Monitor 1' is very low res, and Main Monitor is MUCH higher. Try setting them to about the same resolution to get started.

Try clicking the 'Unused' drop-down and it *should* give you some view settings. Or try setting Monitor 1 to 'Unused' and then try the Main Monitor again.

Your MacBook display will almost certainly go offline when you close the MacBook- try opening that and you should see 3 settings panels (I hope :).


commented by (22 points)

OK, just before heading to bed (22:32 here):  I followed your suggestions and it seems to do exactly what I want from a single machine and a single instance.

However, I had a long struggle with graphic setup before I realised that the monitors panel in X-Plane mimics the arrangement panel in the System Preferences.  That made for some scrollling before I could get to the offset fields.

Now I will have to do this with a PC and Windows, no way out of that.

So, if I get that fabulous card that handles 6 screens, the card may make it look like a 3x2 array, something like this:

Therefore the next thing to check is whether I can put any view on any of these screens, e.g. if 1 and 2 make up the main forward view, can 3 be the view to the left of 1, 4 that to the right of 2 etc.  I think so, but I'll have to put the question to a PC salesman.  So back to the 1000Ordi shop in the next few days.

Ultimately there will be nothing like trying it out on a real configuration, but that costs a lot of money if it does not work out.