NATed guests displaying on Xwindows server ouch

[andya11p]

Running Virtual Box on a mac Sierra.

Two guest OS VM's - one Ubuntu 14.04.something, the other 16.04.something.
Both are Ubuntu servers having no main windowing gui code in them.

Each one runs a Drupal (i.e. htt p with Apache) server that is a copy of an in-use server on a remote host - they run the same drupal code and I'm working on some problems with the server under U16.04 that I don't have under U14.04 (related to different versions of php).

Each is networked with NAT.
To see the served content on each I start Firefox (about v50) on each displaying to X11 server software XQuartz 2.7.11 - that much all works fine and is a reasonable way to work.

BUT: when both VM's are running and I have one instance of FF running on one server and another instance running on the other, both instances displaying to the X server on the Mac one of the instances shows the wrong content - it shows the same content as the other instance even though they are completely isolated by NAT and I whether I use "localhost" or the IP addresses to access the content. Baffled. When I run each alone (the other VM not runnning) the results are what they should be. Its behaving as if there is only *one* FF running. Also, when I quit FF on one server the other one quits too!!!!!!
I cannot figure this out - what's going on ?????? Its as if each server is interfering with the other.

Is XQuartz an implementation of Quantum Mechanics with respect to clients displaying on it ?

Seriously - anyone know ? X11 is old hat I know but its really useful, running a full windowing gui is a lot of overhead.

andy

[Martin]

That's a feature of Firefox.
You need to start it with the -no-remote parameter to use seperate instances.

[andya11p]

Brilliant. Thank you -andy