Comment 2 for bug 1030853

OK. I've found the problem. In function receive_broadcast() defined in /usr/share/epoptes/client-functions, we have the following structure:

if [ -z "$VNCVIEWER" ]; then
    # ssvncviewer is one of the few that can cope with 24bpp (LP: #953512)
    if grep -q "Depth 24 pixmap format is 24 bpp" /var/log/Xorg.?.log &&
        [ -x /usr/bin/ssvncviewer ]
    then
        VNCVIEWER=ssvncviewer
    else
        VNCVIEWER=xvnc4viewer
    fi
fi

In my case, VNCVIEWER is not set and my multiseat settings don't match the if-clause above (namely, my graphics is not 24bpp), so it always try to run xvnc4viewer. But I removed xvnc4viewer after installing ssvnc, so Epoptes silently fails to start broadcasting, because xvnc4viewer is not found.

Replacing the structure above with this one solved my problem, wheter I set VNCVIEWER or not:

if [ -z "$VNCVIEWER" ]; then
    # Always prefer ssvncviewer over xvnc4viewer
    if [ -x /usr/bin/ssvncviewer ]
    then
        VNCVIEWER=ssvncviewer
    else
        VNCVIEWER=xvnc4viewer
    fi
fi