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
