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\ No newline at end of file +[](https://travis-ci.org/LibVNC/libvncserver) [](https://ci.appveyor.com/project/bk138/libvncserver/branch/master) + +LibVNCServer: A library for easy implementation of a VNC server. +Copyright (C) 2001-2003 Johannes E. Schindelin + +If you already used LibVNCServer, you probably want to read NEWS. + +What is it? +=========== + +VNC is a set of programs using the RFB (Remote Frame Buffer) protocol. They +are designed to "export" a frame buffer via net (if you don't know VNC, I +suggest you read "Basics" below). It is already in wide use for +administration, but it is not that easy to program a server yourself. + +This has been changed by LibVNCServer. + +There are two examples included: + - example, a shared scribble sheet + - pnmshow, a program to show PNMs (pictures) over the net. + +The examples are not too well documented, but easy straight forward and a +good starting point. + +Try example: it outputs on which port it listens (default: 5900), so it is +display 0. To view, call + `vncviewer :0` +You should see a sheet with a gradient and "Hello World!" written on it. Try +to paint something. Note that every time you click, there is some bigger blot, +whereas when you drag the mouse while clicked you draw a line. The size of the +blot depends on the mouse button you click. Open a second vncviewer with +the same parameters and watch it as you paint in the other window. This also +works over internet. You just have to know either the name or the IP of your +machine. Then it is + `vncviewer machine.where.example.runs.com:0` +or similar for the remote client. Now you are ready to type something. Be sure +that your mouse sits still, because every time the mouse moves, the cursor is +reset to the position of the pointer! If you are done with that demo, press +the down or up arrows. If your viewer supports it, then the dimensions of the +sheet change. Just press Escape in the viewer. Note that the server still +runs, even if you closed both windows. When you reconnect now, everything you +painted and wrote is still there. You can press "Page Up" for a blank page. + +The demo pnmshow is much simpler: you either provide a filename as argument +or pipe a file through stdin. Note that the file has to be a raw pnm/ppm file, +i.e. a truecolour graphics. Only the Escape key is implemented. This may be +the best starting point if you want to learn how to use LibVNCServer. You +are confronted with the fact that the bytes per pixel can only be 8, 16 or 32. + +If you want to build a VNC client instead, please have a look at the [various +client examples](./client_examples). + +Projects using it +================= + +VNC for KDE +http://www.tjansen.de/krfb + +GemsVNC +http://www.elilabs.com/~rj/gemsvnc/ + +VNC for Netware +http://forge.novell.com/modules/xfmod/project/?vncnw + +RDesktop +http://rdesktop.sourceforge.net + +VNCpp +https://github.com/ocrespo/VNCpp + +VirtualBox +https://www.virtualbox.org/ + +Veyon +https://veyon.io + +Mail me, if your application is missing! + +How to build +============ + +LibVNCServer uses CMake, so you can build via: + + mkdir build + cd build + cmake .. + cmake --build . + +For some more comprehensive examples that include installation of dependencies, see +the [Unix CI](.travis.yml) and [Windows CI](.appveyor.yml) build setups. + +Crosscompiling involves some more advanced command line switches but is easily possible +as well. + +For instance, building for Android (see https://developer.android.com/ndk/guides/cmake.html as a reference): + + mkdir build + cd build + cmake .. -DANDROID_NDK=<path> -DCMAKE_TOOLCHAIN_FILE=<path> -DANDROID_NATIVE_API_LEVEL=<API level you want> -DWITH_PNG=OFF # NDK not shipping png per default + cmake --build . + + +How to use +========== + +To make a server, you just have to initialise a server structure using the +function rfbDefaultScreenInit, like + rfbScreenInfoPtr rfbScreen = + rfbGetScreen(argc,argv,width,height,8,3,bpp); +where byte per pixel should be 1, 2 or 4. If performance doesn't matter, +you may try bpp=3 (internally one cannot use native data types in this +case; if you want to use this, look at pnmshow24). + + +You then can set hooks and io functions (see below) or other +options (see below). + +And you allocate the frame buffer like this: + rfbScreen->frameBuffer = (char*)malloc(width*height*bpp); + +After that, you initialize the server, like + rfbInitServer(rfbScreen); + +You can use a blocking event loop, a background (pthread based) event loop, +or implement your own using the rfbProcessEvents function. + +Making it interactive +--------------------- + +Input is handled by IO functions (see below). + +Whenever you change something in the frame buffer, call rfbMarkRectAsModified. + +Utility functions +----------------- + +Whenever you draw something, you have to call + rfbMarkRectAsModified(screen,x1,y1,x2,y2). +This tells LibVNCServer to send updates to all connected clients. + +Before you draw something, be sure to call + rfbUndrawCursor(screen). +This tells LibVNCServer to hide the cursor. +Remark: There are vncviewers out there, which know a cursor encoding, so +that network traffic is low, and also the cursor doesn't need to be +drawn the cursor every time an update is sent. LibVNCServer handles +all the details. Just set the cursor and don't bother any more. + +To set the mouse coordinates (or emulate mouse clicks), call + rfbDefaultPtrAddEvent(buttonMask,x,y,cl); +IMPORTANT: do this at the end of your function, because this actually draws +the cursor if no cursor encoding is active. + +What is the difference between rfbScreenInfoPtr and rfbClientPtr? +----------------------------------------------------------------- + +The rfbScreenInfoPtr is a pointer to a rfbScreenInfo structure, which +holds information about the server, like pixel format, io functions, +frame buffer etc. + +The rfbClientPtr is a pointer to an rfbClientRec structure, which holds +information about a client, like pixel format, socket of the +connection, etc. + +A server can have several clients, but needn't have any. So, if you +have a server and three clients are connected, you have one instance +of a rfbScreenInfo and three instances of rfbClientRec's. + +The rfbClientRec structure holds a member + rfbScreenInfoPtr screen +which points to the server and a member + rfbClientPtr next +to the next client. + +The rfbScreenInfo structure holds a member + rfbClientPtr rfbClientHead +which points to the first client. + +So, to access the server from the client structure, you use client->screen. +To access all clients from a server, get screen->rfbClientHead and +iterate using client->next. + +If you change client settings, be sure to use the provided iterator + rfbGetClientIterator(rfbScreen) +with + rfbClientIteratorNext(iterator) +and + rfbReleaseClientIterator +to prevent thread clashes. + +Other options +------------- + +These options have to be set between rfbGetScreen and rfbInitServer. + +If you already have a socket to talk to, just set rfbScreen->inetdSock +(originally this is for inetd handling, but why not use it for your purpose?). + +To also start an HTTP server (running on port 5800+display_number), you have +to set rfbScreen->httpdDir to a directory containing vncviewer.jar and +index.vnc (like the included "webclients" directory). + +Hooks and IO functions +---------------------- + +There exist the following IO functions as members of rfbScreen: +kbdAddEvent, kbdReleaseAllKeys, ptrAddEvent and setXCutText + +kbdAddEvent(rfbBool down,rfbKeySym key,rfbClientPtr cl) + is called when a key is pressed. +kbdReleaseAllKeys(rfbClientPtr cl) + is not called at all (maybe in the future). +ptrAddEvent(int buttonMask,int x,int y,rfbClientPtr cl) + is called when the mouse moves or a button is pressed. + WARNING: if you want to have proper cursor handling, call + rfbDefaultPtrAddEvent(buttonMask,x,y,cl) + in your own function. This sets the coordinates of the cursor. +setXCutText(char* str,int len,rfbClientPtr cl) + is called when the selection changes. + +There are only two hooks: +newClientHook(rfbClientPtr cl) + is called when a new client has connected. +displayHook + is called just before a frame buffer update is sent. + +You can also override the following methods: +getCursorPtr(rfbClientPtr cl) + This could be used to make an animated cursor (if you really want ...) +setTranslateFunction(rfbClientPtr cl) + If you insist on colour maps or something more obscure, you have to + implement this. Default is a trueColour mapping. + +Cursor handling +--------------- + +The screen holds a pointer + rfbCursorPtr cursor +to the current cursor. Whenever you set it, remember that any dynamically +created cursor (like return value from rfbMakeXCursor) is not free'd! + +The rfbCursor structure consists mainly of a mask and a source. The mask +describes, which pixels are drawn for the cursor (a cursor needn't be +rectangular). The source describes, which colour those pixels should have. + +The standard is an XCursor: a cursor with a foreground and a background +colour (stored in backRed,backGreen,backBlue and the same for foreground +in a range from 0-0xffff). Therefore, the arrays "mask" and "source" +contain pixels as single bits stored in bytes in MSB order. The rows are +padded, such that each row begins with a new byte (i.e. a 10x4 +cursor's mask has 2x4 bytes, because 2 bytes are needed to hold 10 bits). + +It is however very easy to make a cursor like this: + +char* cur=" " + " xx " + " x " + " "; +char* mask="xxxx" + "xxxx" + "xxxx" + "xxx "; +rfbCursorPtr c=rfbMakeXCursor(4,4,cur,mask); + +You can even set "mask" to NULL in this call and LibVNCServer will calculate +a mask for you (dynamically, so you have to free it yourself). + +There is also an array named "richSource" for colourful cursors. They have +the same format as the frameBuffer (i.e. if the server is 32 bit, +a 10x4 cursor has 4x10x4 bytes). + +History +======= + +LibVNCServer is based on Tridia VNC and OSXvnc, which in turn are based on +the original code from ORL/AT&T. + +When I began hacking with computers, my first interest was speed. So, when I +got around assembler, I programmed the floppy to do much of the work, because +its clock rate was higher than that of my C64. This was my first experience +with client/server techniques. + +When I came around Xwindows (much later), I was at once intrigued by the +elegance of such connectedness between the different computers. I used it +a lot - not the least priority lay on games. However, when I tried it over +modem from home, it was no longer that much fun. + +When I started working with ASP (Application Service Provider) programs, I +tumbled across Tarantella and Citrix. Being a security fanatic, the idea of +running a server on windows didn't appeal to me, so Citrix went down the +basket. However, Tarantella has its own problems (security as well as the +high price). But at the same time somebody told me about this "great little +administrator's tool" named VNC. Being used to windows programs' sizes, the +surprise was reciprocal inverse to the size of VNC! + +At the same time, the program "rdesktop" (a native Linux client for the +Terminal Services of Windows servers) came to my attention. There where even +works under way to make a protocol converter "rdp2vnc" out of this. However, +my primary goal was a slow connection and rdp2vnc could only speak RRE +encoding, which is not that funny with just 5kB/s. Tim Edmonds, the original +author of rdp2vnc, suggested that I adapt it to Hextile Encoding, which is +better. I first tried that, but had no success at all (crunchy pictures). + +Also, I liked the idea of an HTTP server included and possibly other +encodings like the Tight Encodings from Const Kaplinsky. So I started looking +for libraries implementing a VNC server where I could steal what I can't make. +I found some programs based on the demo server from AT&T, which was also the +basis for rdp2vnc (can only speak Raw and RRE encoding). There were some +rumors that GGI has a VNC backend, but I didn't find any code, so probably +there wasn't a working version anyway. + +All of a sudden, everything changed: I read on freshmeat that "OSXvnc" was +released. I looked at the code and it was not much of a problem to work out +a simple server - using every functionality there is in Xvnc. It became clear +to me that I *had* to build a library out of it, so everybody can use it. +Every change, every new feature can propagate to every user of it. + +It also makes everything easier: + You don't care about the cursor, once set (or use the standard cursor). +You don't care about those sockets. You don't care about encodings. +You just change your frame buffer and inform the library about it. Every once +in a while you call rfbProcessEvents and that's it. + +Basics +====== + +VNC (Virtual network computing) works like this: You set up a server and can +connect to it via vncviewers. The communication uses a protocol named RFB +(Remote Frame Buffer). If the server supports HTTP, you can also connect +using a java enabled browser. In this case, the server sends back a +vncviewer applet with the correct settings. + +There exist several encodings for VNC, which are used to compress the regions +which have changed before they are sent to the client. A client need not be +able to understand every encoding, but at least Raw encoding. Which encoding +it understands is negotiated by the RFB protocol. + +The following encodings are known to me: +Raw, RRE, CoRRE, Hextile, CopyRect from the original AT&T code and +Tight, ZLib, LastRect, XCursor, RichCursor from Const Kaplinsky et al. + +If you are using a modem, you want to try the "new" encodings. Especially +with my 56k modem I like ZLib or Tight with Quality 0. In my tests, it even +beats Tarantella. + +There is the possibility to set a password, which is also negotiated by the +RFB protocol, but IT IS NOT SECURE. Anybody sniffing your net can get the +password. You really should tunnel through SSH. + +Windows or: why do you do that to me? +===================================== + +If you love products from Redmod, you better skip this paragraph. +I am always amazed how people react whenever Microsoft(tm) puts in some +features into their products which were around for a long time. Especially +reporters seem to not know dick about what they are reporting about! But +what is every time annoying again, is that they don't do it right. Every +concept has its new name (remember what enumerators used to be until +Mickeysoft(tm) claimed that enumerators are what we thought were iterators. +Yeah right, enumerators are also containers. They are not separated. Muddy.) + +There are three packages you want to get hold of: zlib, jpeg and pthreads. +The latter is not strictly necessary, but when you put something like this +into your source: + +``` +#define MUTEX(s) + struct { + int something; + MUTEX(latex); + } +``` + +Microsoft's C++ compiler doesn't do it. It complains that this is an error. +This, however, is how I implemented mutexes in case you don't need pthreads, +and so don't need the mutex. + +You can find the packages at +http://www.gimp.org/win32/extralibs-dev-20001007.zip + +Thanks go to all the GIMP team! + +What are those other targets in the Makefile? +============================================= + +OSXvnc-server is the original OSXvnc adapted to use the library, which was in +turn adapted from OSXvnc. As you easily can see, the OSX dependend part is +minimal. + +storepasswd is the original program to save a vnc style password in a file. +Unfortunately, authentication as every vncviewer speaks it means the server +has to know the plain password. You really should tunnel via ssh or use +your own PasswordCheck to build a PIN/TAN system. + +sratest is a test unit. Run it to assert correct behaviour of sraRegion. I +wrote this to test my iterator implementation. + +blooptest is a test of pthreads. It is just the example, but with a background +loop to hunt down thread lockups. + +pnmshow24 is like pnmshow, but it uses 3 bytes/pixel internally, which is not +as efficient as 4 bytes/pixel for translation, because there is no native data +type of that size, so you have to memcpy pixels and be real cautious with +endianness. Anyway, it works. + +fontsel is a test for rfbSelectBox and rfbLoadConsoleFont. If you have Linux +console fonts, you can browse them via VNC. Directory browsing not implemented +yet :-( + +Why I don't feel bad about GPL +============================== + +At the beginning of this projects I would have liked to make it a BSD +license. However, it is based on plenty of GPL'ed code, so it has to be +a GPL. I hear BeeGee complaining: "but that's invasive, every derivative +work, even just linking, makes my software GPL!" + +Yeah. That's right. It is because there are nasty jarheads out there who +would take anybody's work and claim it their own, selling it for much too +much money, stealing freedom and innovation from others, saying they were +the maintainers of innovation, lying, making money with that. + +The people at AT&T worked really well to produce something as clean and lean +as VNC. The managers decided that for their fame, they would release the +program for free. But not only that! They realized that by releasing also +the code for free, VNC would become an evolving little child, conquering +new worlds, making its parents very proud. As well they can be! To protect +this innovation, they decided to make it GPL, not BSD. The principal +difference is: You can make closed source programs deriving from BSD, not +from GPL. You have to give proper credit with both. + +Now, why not BSD? Well, imagine your child being some famous actor. Along +comes a manager who exploits your child exclusively, that is: nobody else +can profit from the child, it itself included. Got it? + +What reason do you have now to use this library commercially? + +Several: You don't have to give away your product. Then you have effectively +circumvented the GPL, because you have the benefits of other's work and you +don't give back anything and you will be in hell for that. In fact, this +library, as my other projects, is a payback for all the free software I can +use (and sometimes, make better). For example, just now, I am using XEmacs +on top of XFree86, all running under Linux. + +Better: Use a concept like MySQL. This is free software, however, they make +money with it. If you want something implemented, you have the choice: +Ask them to do it (and pay a fair price), or do it yourself, normally giving +back your enhancements to the free world of computing. + +Learn from it: If you like the style this is written, learn how to imitate +it. If you don't like the style, learn how to avoid those things you don't +like. I learnt so much, just from looking at code like Linux, XEmacs, +LilyPond, STL, etc. + +License +------- + +This program is free software; you can redistribute it and/or +modify it under the terms of the GNU General Public License +as published by the Free Software Foundation; either version 2 +of the License, or (at your option) any later version. + +This program is distributed in the hope that it will be useful, +but WITHOUT ANY WARRANTY; without even the implied warranty of +MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +GNU General Public License for more details. + +You should have received a copy of the GNU General Public License +along with this program; if not, write to the Free Software +Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.dfdf + +Contact +======= + +To contact me, mail me: Johannes dot Schindelin at gmx dot de + |