1 LibVNCServer: A library for easy implementation of a VNC server.
2 Copyright (C) 2001-2003 Johannes E. Schindelin
3
4 If you already used LibVNCServer, you probably want to read NEWS.
5
6 What is it?
7 -----------
8
9 VNC is a set of programs using the RFB (Remote Frame Buffer) protocol. They
10 are designed to "export" a frame buffer via net (if you don't know VNC, I
11 suggest you read "Basics" below). It is already in wide use for
12 administration, but it is not that easy to program a server yourself.
13
14 This has been changed by LibVNCServer.
15
16 There are two examples included:
17 - example, a shared scribble sheet
18 - pnmshow, a program to show PNMs (pictures) over the net.
19
20 The examples are not too well documented, but easy straight forward and a
21 good starting point.
22
23 Try example: it outputs on which port it listens (default: 5900), so it is
24 display 0. To view, call
25 vncviewer :0
26 You should see a sheet with a gradient and "Hello World!" written on it. Try
27 to paint something. Note that everytime you click, there is some bigger blot,
28 whereas when you drag the mouse while clicked you draw a line. The size of the
29 blot depends on the mouse button you click. Open a second vncviewer with
30 the same parameters and watch it as you paint in the other window. This also
31 works over internet. You just have to know either the name or the IP of your
32 machine. Then it is
33 vncviewer machine.where.example.runs.com:0
34 or similar for the remote client. Now you are ready to type something. Be sure
35 that your mouse sits still, because everytime the mouse moves, the cursor is
36 reset to the position of the pointer! If you are done with that demo, press
37 the down or up arrows. If your viewer supports it, then the dimensions of the
38 sheet change. Just press Escape in the viewer. Note that the server still
39 runs, even if you closed both windows. When you reconnect now, everything you
40 painted and wrote is still there. You can press "Page Up" for a blank page.
41
42 The demo pnmshow is much simpler: you either provide a filename as argument
43 or pipe a file through stdin. Note that the file has to be a raw pnm/ppm file,
44 i.e. a truecolour graphics. Only the Escape key is implemented. This may be
45 the best starting point if you want to learn how to use LibVNCServer. You
46 are confronted with the fact that the bytes per pixel can only be 8, 16 or 32.
47
48 Projects using it
49 ----------------------------------------
50
51 VNC for KDE
52 http://www.tjansen.de/krfb
53
54 GemsVNC
55 http://www.elilabs.com/~rj/gemsvnc/
56
57 VNC for Netware
58 http://forge.novell.com/modules/xfmod/project/?vncnw
59
60 RDesktop
61 http://rdesktop.sourceforge.net
62
63 Mail me, if your application is missing!
64
65 How to use
66 ----------
67
68 To make a server, you just have to initialise a server structure using the
69 function rfbDefaultScreenInit, like
70 rfbScreenInfoPtr rfbScreen =
71 rfbGetScreen(argc,argv,width,height,8,3,bpp);
72 where byte per pixel should be 1, 2 or 4. If performance doesn't matter,
73 you may try bpp=3 (internally one cannot use native data types in this
74 case; if you want to use this, look at pnmshow24).
75
76
77 You then can set hooks and io functions (see below) or other
78 options (see below).
79
80 And you allocate the frame buffer like this:
81 rfbScreen->frameBuffer = (char*)malloc(width*height*bpp);
82
83 After that, you initialize the server, like
84 rfbInitServer(rfbScreen);
85
86 You can use a blocking event loop, a background (pthread based) event loop,
87 or implement your own using the rfbProcessEvents function.
88
89 Making it interactive
90 ---------------------
91
92 Input is handled by IO functions (see below).
93
94 Whenever you change something in the frame buffer, call rfbMarkRectAsModified.
95 You should make sure that the cursor is not drawn before drawing yourself
96 by calling rfbUndrawCursor. You can also draw the cursor using rfbDrawCursor,
97 but it hardly seems necessary. For cursor details, see below.
98
99 Utility functions
100 -----------------
101
102 Whenever you draw something, you have to call
103 rfbMarkRectAsModified(screen,x1,y1,x2,y2).
104 This tells LibVNCServer to send updates to all connected clients.
105
106 Before you draw something, be sure to call
107 rfbUndrawCursor(screen).
108 This tells LibVNCServer to hide the cursor.
109 Remark: There are vncviewers out there, which know a cursor encoding, so
110 that network traffic is low, and also the cursor doesn't need to be
111 drawn the cursor everytime an update is sent. LibVNCServer handles
112 all the details. Just set the cursor and don't bother any more.
113
114 To set the mouse coordinates (or emulate mouse clicks), call
115 defaultPtrAddEvent(buttonMask,x,y,cl);
116 IMPORTANT: do this at the end of your function, because this actually draws
117 the cursor if no cursor encoding is active.
118
119 What is the difference between rfbScreenInfoPtr and rfbClientPtr?
120 -----------------------------------------------------------------
121
122 The rfbScreenInfoPtr is a pointer to a rfbScreenInfo structure, which
123 holds information about the server, like pixel format, io functions,
124 frame buffer etc.
125
126 The rfbClientPtr is a pointer to an rfbClientRec structure, which holds
127 information about a client, like pixel format, socket of the
128 connection, etc.
129
130 A server can have several clients, but needn't have any. So, if you
131 have a server and three clients are connected, you have one instance
132 of a rfbScreenInfo and three instances of rfbClientRec's.
133
134 The rfbClientRec structure holds a member
135 rfbScreenInfoPtr screen
136 which points to the server and a member
137 rfbClientPtr next
138 to the next client.
139
140 The rfbScreenInfo structure holds a member
141 rfbClientPtr rfbClientHead
142 which points to the first client.
143
144 So, to access the server from the client structure, you use client->screen.
145 To access all clients from a server, get screen->rfbClientHead and
146 iterate using client->next.
147
148 If you change client settings, be sure to use the provided iterator
149 rfbGetClientIterator(rfbScreen)
150 with
151 rfbClientIteratorNext(iterator)
152 and
153 rfbReleaseClientIterator
154 to prevent thread clashes.
155
156 Other options
157 -------------
158
159 These options have to be set between rfbGetScreen and rfbInitServer.
160
161 If you already have a socket to talk to, just set rfbScreen->inetdSock
162 (originally this is for inetd handling, but why not use it for your purpose?).
163
164 To also start an HTTP server (running on port 5800+display_number), you have
165 to set rfbScreen->httpdDir to a directory containing vncviewer.jar and
166 index.vnc (like the included "webclients" directory).
167
168 Hooks and IO functions
169 ----------------------
170
171 There exist the following IO functions as members of rfbScreen:
172 kbdAddEvent, kbdReleaseAllKeys, ptrAddEvent and setXCutText
173
174 kbdAddEvent(rfbBool down,rfbKeySym key,rfbClientPtr cl)
175 is called when a key is pressed.
176 kbdReleaseAllKeys(rfbClientPtr cl)
177 is not called at all (maybe in the future).
178 ptrAddEvent(int buttonMask,int x,int y,rfbClientPtr cl)
179 is called when the mouse moves or a button is pressed.
180 WARNING: if you want to have proper cursor handling, call
181 defaultPtrAddEvent(buttonMask,x,y,cl)
182 in your own function. This sets the coordinates of the cursor.
183 setXCutText(char* str,int len,rfbClientPtr cl)
184 is called when the selection changes.
185
186 There are only two hooks:
187 newClientHook(rfbClientPtr cl)
188 is called when a new client has connected.
189 displayHook
190 is called just before a frame buffer update is sent.
191
192 You can also override the following methods:
193 getCursorPtr(rfbClientPtr cl)
194 This could be used to make an animated cursor (if you really want ...)
195 setTranslateFunction(rfbClientPtr cl)
196 If you insist on colour maps or something more obscure, you have to
197 implement this. Default is a trueColour mapping.
198
199 Cursor handling
200 ---------------
201
202 The screen holds a pointer
203 rfbCursorPtr cursor
204 to the current cursor. Whenever you set it, remember that any dynamically
205 created cursor (like return value from rfbMakeXCursor) is not free'd!
206
207 The rfbCursor structure consists mainly of a mask and a source. The mask
208 describes, which pixels are drawn for the cursor (a cursor needn't be
209 rectangular). The source describes, which colour those pixels should have.
210
211 The standard is an XCursor: a cursor with a foreground and a background
212 colour (stored in backRed,backGreen,backBlue and the same for foreground
213 in a range from 0-0xffff). Therefore, the arrays "mask" and "source"
214 contain pixels as single bits stored in bytes in MSB order. The rows are
215 padded, such that each row begins with a new byte (i.e. a 10x4
216 cursor's mask has 2x4 bytes, because 2 bytes are needed to hold 10 bits).
217
218 It is however very easy to make a cursor like this:
219
220 char* cur=" "
221 " xx "
222 " x "
223 " ";
224 char* mask="xxxx"
225 "xxxx"
226 "xxxx"
227 "xxx ";
228 rfbCursorPtr c=rfbMakeXCursor(4,4,cur,mask);
229
230 You can even set "mask" to NULL in this call and LibVNCServer will calculate
231 a mask for you (dynamically, so you have to free it yourself).
232
233 There is also an array named "richSource" for colourful cursors. They have
234 the same format as the frameBuffer (i.e. if the server is 32 bit,
235 a 10x4 cursor has 4x10x4 bytes).
236
237 History
238 -------
239
240 LibVNCServer is based on Tridia VNC and OSXvnc, which in turn are based on
241 the original code from ORL/AT&T.
242
243 When I began hacking with computers, my first interest was speed. So, when I
244 got around assembler, I programmed the floppy to do much of the work, because
245 it's clock rate was higher than that of my C64. This was my first experience
246 with client/server techniques.
247
248 When I came around Xwindows (much later), I was at once intrigued by the
249 elegance of such connectedness between the different computers. I used it
250 a lot - not the least priority lay on games. However, when I tried it over
251 modem from home, it was no longer that much fun.
252
253 When I started working with ASP (Application Service Provider) programs, I
254 tumbled across Tarantella and Citrix. Being a security fanatic, the idea of
255 running a server on windows didn't appeal to me, so Citrix went down the
256 basket. However, Tarantella has it's own problems (security as well as the
257 high price). But at the same time somebody told me about this "great little
258 administrator's tool" named VNC. Being used to windows programs' sizes, the
259 surprise was reciprocal inverse to the size of VNC!
260
261 At the same time, the program "rdesktop" (a native Linux client for the
262 Terminal Services of Windows servers) came to my attention. There where even
263 works under way to make a protocol converter "rdp2vnc" out of this. However,
264 my primary goal was a slow connection and rdp2vnc could only speak RRE
265 encoding, which is not that funny with just 5kB/s. Tim Edmonds, the original
266 author of rdp2vnc, suggested that I adapt it to Hextile Encoding, which is
267 better. I first tried that, but had no success at all (crunchy pictures).
268
269 Also, I liked the idea of an HTTP server included and possibly other
270 encodings like the Tight Encodings from Const Kaplinsky. So I started looking
271 for libraries implementing a VNC server where I could steal what I can't make.
272 I found some programs based on the demo server from AT&T, which was also the
273 basis for rdp2vnc (can only speak Raw and RRE encoding). There were some
274 rumors that GGI has a VNC backend, but I didn't find any code, so probably
275 there wasn't a working version anyway.
276
277 All of a sudden, everything changed: I read on freshmeat that "OSXvnc" was
278 released. I looked at the code and it was not much of a problem to work out
279 a simple server - using every functionality there is in Xvnc. It became clear
280 to me that I *had* to build a library out of it, so everybody can use it.
281 Every change, every new feature can propagate to every user of it.
282
283 It also makes everything easier:
284 You don't care about the cursor, once set (or use the standard cursor).
285 You don't care about those sockets. You don't care about encodings.
286 You just change your frame buffer and inform the library about it. Every once
287 in a while you call rfbProcessEvents and that's it.
288
289 Basics
290 ------
291
292 VNC (Virtual network computing) works like this: You set up a server and can
293 connect to it via vncviewers. The communication uses a protocol named RFB
294 (Remote Frame Buffer). If the server supports HTTP, you can also connect
295 using a java enabled browser. In this case, the server sends back a
296 vncviewer applet with the correct settings.
297
298 There exist several encodings for VNC, which are used to compress the regions
299 which have changed before they are sent to the client. A client need not be
300 able to understand every encoding, but at least Raw encoding. Which encoding
301 it understands is negotiated by the RFB protocol.
302
303 The following encodings are known to me:
304 Raw, RRE, CoRRE, Hextile, CopyRect from the original AT&T code and
305 Tight, ZLib, LastRect, XCursor, RichCursor from Const Kaplinsky et al.
306
307 If you are using a modem, you want to try the "new" encodings. Especially
308 with my 56k modem I like ZLib or Tight with Quality 0. In my tests, it even
309 beats Tarantella.
310
311 There is the possibility to set a password, which is also negotiated by the
312 RFB protocol, but IT IS NOT SECURE. Anybody sniffing your net can get the
313 password. You really should tunnel through SSH.
314
315 Windows or: why do you do that to me?
316 --------------------------------------------
317
318 If you love products from Redmod, you better skip this paragraph.
319 I am always amazed how people react whenever Microsoft(tm) puts in some
320 features into their products which were around for a long time. Especially
321 reporters seem to not know dick about what they are reporting about! But
322 what is everytime annoying again, is that they don't do it right. Every
323 concept has it's new name (remember what enumerators used to be until
324 Mickeysoft(tm) claimed that enumerators are what we thought were iterators.
325 Yeah right, enumerators are also containers. They are not separated. Muddy.)
326
327 There are three packages you want to get hold of: zlib, jpeg and pthreads.
328 The latter is not strictly necessary, but when you put something like this
329 into your source:
330
331 #define MUTEX(s)
332 struct {
333 int something;
334 MUTEX(latex);
335 }
336
337 Microsoft's C++ compiler doesn't do it. It complains that this is an error.
338 This, however, is how I implemented mutexes in case you don't need pthreads,
339 and so don't need the mutex.
340
341 You can find the packages at
342 http://www.gimp.org/win32/extralibs-dev-20001007.zip
343
344 Thanks go to all the GIMP team!
345
346 What are those other targets in the Makefile?
347 ---------------------------------------------
348
349 OSXvnc-server is the original OSXvnc adapted to use the library, which was in
350 turn adapted from OSXvnc. As you easily can see, the OSX dependend part is
351 minimal.
352
353 storepasswd is the original program to save a vnc style password in a file.
354 Unfortunately, authentication as every vncviewer speaks it means the server
355 has to know the plain password. You really should tunnel via ssh or use
356 your own PasswordCheck to build a PIN/TAN system.
357
358 sratest is a test unit. Run it to assert correct behaviour of sraRegion. I
359 wrote this to test my iterator implementation.
360
361 blooptest is a test of pthreads. It is just the example, but with a background
362 loop to hunt down thread lockups.
363
364 pnmshow24 is like pnmshow, but it uses 3 bytes/pixel internally, which is not
365 as efficient as 4 bytes/pixel for translation, because there is no native data
366 type of that size, so you have to memcpy pixels and be real cautious with
367 endianness. Anyway, it works.
368
369 fontsel is a test for rfbSelectBox and rfbLoadConsoleFont. If you have Linux
370 console fonts, you can browse them via VNC. Directory browsing not implemented
371 yet :-(
372
373 Why I don't feel bad about GPL
374 ------------------------------
375
376 At the beginning of this projects I would have liked to make it a BSD
377 license. However, it is based on plenty of GPL'ed code, so it has to be
378 a GPL. I hear BeeGee complaining: "but that's invasive, every derivative
379 work, even just linking, makes my software GPL!"
380
381 Yeah. That's right. It is because there are nasty jarheads out there who
382 would take anybody's work and claim it their own, selling it for much too
383 much money, stealing freedom and innovation from others, saying they were
384 the maintainers of innovation, lying, making money with that.
385
386 The people at AT&T worked really well to produce something as clean and lean
387 as VNC. The managers decided that for their fame, they would release the
388 program for free. But not only that! They realized that by releasing also
389 the code for free, VNC would become an evolving little child, conquering
390 new worlds, making it's parents very proud. As well they can be! To protect
391 this innovation, they decided to make it GPL, not BSD. The principal
392 difference is: You can make closed source programs deriving from BSD, not
393 from GPL. You have to give proper credit with both.
394
395 Now, why not BSD? Well, imagine your child being some famous actor. Along
396 comes a manager who exploits your child exclusively, that is: nobody else
397 can profit from the child, it itself included. Got it?
398
399 What reason do you have now to use this library commercially?
400
401 Several: You don't have to give away your product. Then you have effectively
402 circumvented the GPL, because you have the benefits of other's work and you
403 don't give back anything and you will be in hell for that. In fact, this
404 library, as my other projects, is a payback for all the free software I can
405 use (and sometimes, make better). For example, just now, I am using XEmacs
406 on top of XFree86, all running under Linux.
407
408 Better: Use a concept like MySQL. This is free software, however, they make
409 money with it. If you want something implemented, you have the choice:
410 Ask them to do it (and pay a fair price), or do it yourself, normally giving
411 back your enhancements to the free world of computing.
412
413 Learn from it: If you like the style this is written, learn how to imitate
414 it. If you don't like the style, learn how to avoid those things you don't
415 like. I learnt so much, just from looking at code like Linux, XEmacs,
416 LilyPond, STL, etc.
417
418 License
419 -------
420
421 This program is free software; you can redistribute it and/or
422 modify it under the terms of the GNU General Public License
423 as published by the Free Software Foundation; either version 2
424 of the License, or (at your option) any later version.
425
426 This program is distributed in the hope that it will be useful,
427 but WITHOUT ANY WARRANTY; without even the implied warranty of
428 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
429 GNU General Public License for more details.
430
431 You should have received a copy of the GNU General Public License
432 along with this program; if not, write to the Free Software
433 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.dfdf
434
435 Contact
436 -------
437
438 To contact me, mail me: Johannes dot Schindelin at gmx dot de
439
440