vncviewer allows to specify the display number in the connection string:


  If you run the viewer with no arguments it will prompt you for a VNC
  server to connect to. Alternatively, specify the VNC server as an
  argument, e.g.:  vncviewer snoopy:2
  
  where 'snoopy' is the name of the machine, and '2' is the display
  number of the VNC server on that machine. Either the machine name or
  display number can be omitted. So for example ":1" means display
  number 1 on the same machine, and "snoopy" means "snoopy:0" i.e.
  display 0 on machine "snoopy". 


Source: manpage for vncviewer

I could not find an explicit option in Remmina to specify display number, however:


  By default, a VNC server will listen for connections from a VNC viewer
  on TCP port "5900+N", where N is the "Display Number" (usually just
  zero). So a VNC server setup for Display-0 will listen on TCP-5900,
  Display-1 is TCP-5901, etc.
  
  Additionally, the VNC server will listen for connections from a
  web-browser on TCP port "5800+N", where N is as above. If you point a
  web-browser to this port, the VNC server will automatically provide a
  Java VNC viewer that runs right in your web-browser. This Java Viewer
  will then exchange data with the VNC Server on the same ports a normal
  VNC Viewer would use: "5900+N".


(source)

So I guess you may try to connect to a specific display by specifying port number in connection settings.

Is it possible to connect to already running session on Xubuntu 12.04 machine?
In what way can an android game be tested considering the following constrains:


minimal to no budget, so I cannot hire an external company to do the testing for me
Testing should occur on multiple devices and types (phones and tablets, I have 1 available for each)
I do not have a team of testers, nor a large group of people with android devices willing to back me up.
The game is a multiplayer game (min 2, max 4 players per game) with a
backend that will be hosted on an external server (which is already
arranged), so for every testrun 2 devices are needed.
The game server is not built in java and will be unit tested, the
testing is more about doing integration testing.
Optional is stress testing the game server so we can get some sort of
baseline for this hardware.

