Re: [rdesktop-devel] how to write an MS-Windows-based, RDP-based,client/server software

[Mrs. B. <mrs...@ni...>]

On Sat, 2002-11-02 at 12:50, Assaf Wodeslavsky wrote:
> i don't understand how you can say this.
> i have looked into VNC sources.
> VNC captures areas of the screen as BITMAPS.
> and sends them over the wire.
> RDP on the other hand,
> captures the GDI primitives and sends them.
> correct me if im wrong,
> but a BITMAP is heavier to transfer than a FUNCTION CALL.

Okay, you're wrong.

the ICA protocol actually wraps GDI onto an RPC. RDP is pretty much the
same as VNC- it _seems_slower_ on Win32 because the Windows TS server
can detect what kind of changes occur at the GDI layer.

Because it can detect these things, it can allocate them into structures
that mesh much more neatly onto a protocol stream- which between VNC and
RDP- is fairly similar.

Both greatly resemble message passing, however while RDP has a few extra
layers for different messages, VNC has only one- and all of it is
encoded in this "encoding format" byte.

I suggest you take a look at "Modern Operating Systems" by Andrew S.
Tannenbaum for a good introduction to the difference between RPC and
message passing.

Compare Xvnc versus RDP. Not Win32-VNC with TS-RDP.

> also, at home , i use both VNC and RDP.
> there is no comparison.
> where VNC is so slow that you need to turn it off because it halts the
> computer,
> RDP is ususlly untocible, to the point that you need to check if it is
> running (if you are remote).


I have had many problems with Win32-VNC. Again, I don't think it's fair
or helpful. If you're trying to solve a problem, what good does it do to
have a misconception on how your tools work, and what tools exist for
helping you solve it.


> i really would like to concentrate on either:
> controlling RDP on the server side
> or
> wrting my own RDP server.
> 
> if you can help me with anything like that,
> i would really appreciate it.

Sure. Unless you know that those GDI hooks are for the TS, your _best
bet_ is to take a look at this video driver that I have mentioned.
Surely it is for VNC, but since you looked "at the VNC sources" you
should have no problem using it as a base for writing an RDP server on.