rfb server support

[totaam]

Implementing a bare bones RFB server turned out to be trivial since the protocol is so simple (unlike xpra, no windows or metadata to deal with!): rfc6143.

This may be useful for comparing with VNC clients, debugging the vfb state, etc

TODO before the next release (minimum required for secure usage):

• bug: screen updates are always one frame behind
• authentication step (support at least VncAuth)
• move code to an rfb support module and also support rfb in shadow servers
• honour server sharing options, fix source missing attributes (uuid, etc)
• verify control channel commands, etc (anything that might dereference missing source attributes)

Extras (probably for a later milestone):

• SSL support (should be trivial)
• refactor rfb protocol code into a common superclass with regular xpra protocol (packet accounting, threads, close, etc)
• more encodings than just plain RGB (ie: copyrect for scrolling, jpeg)
• clipboard support
• support colormap modes? (8 / 16 bit)
• desktop-size pseudo encoding (randr like)
• maybe add a default port for bind-rfb (5900 + DISPLAY)
• support older protocols

To use it:

xpra start-desktop :100 --start=xterm --bind-rfb=0.0.0.0:5900 -d rfb
vncviewer 127.0.0.1:0 -Log "*:stderr:100"

[totaam]

Code added in r16673, see also #639.

Better links:

• vncdotool: rfbproto
• iana: rfb

[totaam]

Updates linked to UDP (#639):

• r16710 + r16713: authentication modules refactoring - preparation
• r16712: large rfb update (see commit message)

[totaam]

Should be fully usable as of r16784 (see commit message).
This is useful for testing, but will need work before being able to compete with other RFB servers (#1632).

@maxmylyn: this is just a FYI, feel free to close.

---

It does support authentication and sharing options, ie:

echo -n 01234567 password.txt
xpra start-desktop :100 --start=xterm --sharing=yes \
    --bind-tcp=0.0.0.0: \
    --bind-rfb=0.0.0.0: --rfb-auth=file,filename=./password.txt --no-daemon 

You can then connect with vncviewer:

echo -n 01234567 | vncpasswd -f password.vnc
vncviewer 127.0.0.1:0 -Log "*:stderr:100" -Shared=1 -passwd=./password.vnc

And since sharing is enabled, you can connect an xpra client simultaneously:

xpra attach tcp:localhost

[totaam]

2017-09-06 21:59:59: maxmylyn commented

---

Noted and closing.

[totaam]

As usual, this required a bunch of platform tweaks and fixes:

• better keycode support: r16785, with macos and win32 servers support: r16789
• shadow servers needed to be told to start refreshing: r16786
• handle win32 sockets timeouts: r16787
• mouse button handler method signature requires position on win32: r16788
• platform import fixes, macos doesn't have X11: r16790, r16791
• macos shadow server fixes: r16792, r16794
• TCP sockets can be "upgraded" to RFB after a timeout: r16836

It would be nice to add support for bandwidth-limit (#417)

[totaam]

Regression in v4: #2811.