[winswitch] How data flows through Xpra server and proxy

Antoine Martin antoine at nagafix.co.uk
Fri Nov 18 04:26:14 GMT 2016

On 18/11/16 08:35, Aaditya Shidham via shifter-users wrote:
> Hello,
> I have the following invocation of Xpra:
> xpra start :5455 --bind-tcp= --html=on --no-daemon
> And then I can get graphical programs in an Xpra client to load through
> DISPLAY=:5455 xeyes
Use this instead:
xpra (..) --start=xeyes
So the application won't be killed if your ssh / xterm dies.

> I'm curious how data for the x11 packets go through the Xpra program. It
> seems that Xvfb is what handles the xeyes by storing the display in memory.
> How does this data then pass to the rest of Xpra? According to (
> http://stackoverflow.com/questions/12050021/how-to-make-xvfb-display-visible),
> I need to use -fbdir to access this virtual memory, but this isn't used
> when Xvfb is invoked by Xpra.
xpra is just like any other X11 client application, it connects to the
X11 server using its unix domain sockets and will use shared memory
(XShm) if available (it almost always is).

This does not need "-fbdir" which is specific to Xvfb and serves a
different purpose.

> Also where is the local Unix socket used? I can see where the local domain
> Unix socket is set inside xpra/scripts/server.py, but I don't see where it
> is ever used. It seems to be named partially after the :5455
> (~/.xpra/ip-XXX-XX-XX-5455), but where are the two connected?
That's xpra's socket, which is used for xpra connections, not X11
You can find more details on where this is going here:


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