From: George Patargias (
Date: Thu Nov 01 2012 - 03:26:28 CDT

Thanks a lot for all these comments!
I will try to put all this together
and get back to you in case of problems.

Best wishes

> On Tue, Oct 30, 2012 at 11:57 AM, George Patargias <>
> wrote:
>> Many thanks for your reply; it really clarified a lot.
>> Just a couple of more things, if you don't mind, that occurred to me as
>> I
>> went through the set-up requirements listed in your page.
>> One requirement is the libnifalcon library. Does the installation of
>> libnifalcon come before or a after VRPN installation? How the two
>> installations relate?
> when you compile VRPN you need access to the include
> files and library from libnifalcon, or else you cannot compile
> support for the falcon into VRPN. however, you may not need
> to "install" libnifalcon or its utilities to *use* a falcon enabled
> VRPN server. the library is a static library and thus copied
> into the VRPN server binary. nevertheless, the test programs
> that are bundled with libnifalcon are useful for debugging.
>> In .vmdsensors file, am I right to understand that in
>> "vrpntracker://localhost/Tracker0"
>> "localhost" is the IP address (or hostname?) of the machine that Falcon
>> is
>> connected?
> yes. it is the machine where the VRPN server is running.
>> Do you have any idea which type of USB-2.0 hub would be suitable for a
>> MacOS laptop? In the instructions for calibrating the device and
>> loading
>> the firmware you say that the firmware (after second/third attempt) will
>> not load if the USB is not suitable.
> it has to be a *powered* hub, i.e. a hub that has its
> own power supply. i don't really know what is the
> technical reason for that, and i ran into the rare case
> of seeing a powered hub that was not sufficient.
> it won't exclude that it may work *without* a hub.
> my tests were only only done on Linux. things may
> be different on other operating systems.
>> Is there any standard way to choose TCP port numbers for the VMD/IMD and
>> VRPN/VMD connections?
> for VMD/IMD you are free to choose any
> port that you want. by convention, opening
> ports below 1024 for server processes are
> restricted to the superuser on unix-like
> machines. often ports between 5000 and
> 10000 are chosen. port numbers are 16-bit
> unsigned integer, so 65535 is the largest
> possible port to choose. the command:
> netstat -tan
> (on a linux machines) will show you, which
> ports are currently in use. and the file
> /etc/services typically has a list of ports
> commonly used by known applications.
> VRPN uses a port (3883) usually listed
> in /etc/services for the server to listen to.
> unless you explicitly tell it to use a TCP
> connection, the VRPN protocol will use
> multiple concurrent UDP ports for lower
> latency communication. if you need to
> run through a firewall, you probably want
> to use force TCP instead of UDP. so
> you don't have to deal with the port
> randomization. similarly, if you have to
> forward the port through ssh tunneling
> (which has been successfully done as
> well in the past).
> hope that answers your questions.
> don't hesitate to ask again, if there are
> more or something is not clear in what
> i wrote. it has been a while since i was
> last working with a falcon (in fact, i have
> been physically separated by over 4,500
> miles from it for the last four months).
> regards,
> axel.
>> Thanks again.
>> George
> --
> Dr. Axel Kohlmeyer
> International Centre for Theoretical Physics, Trieste. Italy.

Dr. George Patargias
Postdoctoral Researcher
Biomedical Research Foundation
Academy of Athens
4, Soranou Ephessiou
115 27

Office: +302106597568