## noVNC: HTML5 VNC Client


### Description

noVNC is a VNC client implemented using HTML5 technologies,
specifically Canvas and WebSocket (supports 'wss://' encryption).

For browsers that do not have builtin WebSocket support, the project
includes web-socket-js, a WebSocket emulator using Adobe Flash
(http://github.com/gimite/web-socket-js).

In addition, as3crypto has been added to web-socket-js to implement
WebSocket SSL/TLS encryption, i.e. the "wss://" URI scheme.
(http://github.com/lyokato/as3crypto_patched).


### Requirements

Until there is VNC server support for WebSocket connections, you need
to use a WebSocket to TCP socket proxy. There is a python proxy
included ('wsproxy'). One advantage of using the proxy is that it has
builtin support for SSL/TLS encryption (i.e. "wss://").

There a few reasons why a proxy is required:

  1. WebSocket is not a pure socket protocol. There is an initial HTTP
     like handshake to allow easy hand-off by web servers and allow
     some origin policy exchange. Also, each WebSocket frame begins
     with 0 ('\x00') and ends with 255 ('\xff').

  2. Javascript itself does not have the ability to handle pure byte
     strings (Unicode encoding messes with it) even though you can
     read them with WebSocket. The python proxy encodes the data so
     that the Javascript client can base64 decode the data into an
     array.

  3. When using the web-socket-js as a fallback, WebSocket 'onmessage'
     events may arrive out of order. In order to compensate for this
     the client asks the proxy (using the initial query string) to add
     sequence numbers to each packet.


### Usage

* To encrypt the traffic using the WebSocket 'wss://' URI scheme you
  need to generate a certificate for the proxy to load. You can generate
  a self-signed certificate using openssl. The common name should be the
  hostname of the server where the proxy will be running:

    `openssl req -new -x509 -days 365 -nodes -out self.pem -keyout self.pem`

* run a VNC server.
 
    `vncserver :1`

* run the python proxy:

    `./utils/wsproxy.py -f source_port target_addr:target_port

    `./utils/wsproxy.py -f 8787 localhost:5901`


* run the mini python web server to serve the directory:

    `./utils/web.py PORT`

    `./utils/web.py 8080`

* Point your web browser at http://localhost:8080/vnc.html
 (or whatever port you used above to run the web server).

* Specify the host and port where the proxy is running and the
  password that the vnc server is using (if any). Hit the Connect
  button and enjoy!


### Browser Support

In the following table Jaunty is Ubuntu 9.04 and WinXP is Windows XP.

#### Linux (Ubuntu 9.04)

<table>
    <tr>
        <th>OS</th> <th>Browser</th>
        <th>Status</th>
        <th>Notes</th>
    </tr> <tr>
        <td>Jaunty</td> <td>Chrome 5.0.375.29</td>
        <td>Excellent</td>
        <td>Very fast. Native WebSockets.</td>
    </tr> <tr>
        <td>Jaunty</td> <td>Firefox 3.5</td>
        <td>Good</td>
        <td>Large full-color images are somewhat slow from web-socket-js overhead.</td>
    </tr> <tr>
        <td>Jaunty</td> <td>Opera 10.60</td>
        <td>Poor</td>
        <td>web-socket-js problems, mouse/keyboard issues. See note 1</td>
    </tr> <tr>
        <td>Jaunty</td> <td>Arora 0.5</td>
        <td>Good</td>
        <td>Broken putImageData so large full-color images
            are slow. Uses web-socket-js.</td>
    </tr> <tr>
        <td>Jaunty</td> <td>Konqueror 4.2.2</td>
        <td><strong>Broken</strong></td>
        <td>web-socket-js never loads</td>
    </tr> <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
    </tr> <tr>
        <td>WinXP</td> <td>Chrome 5.0.375.99</td>
        <td>Excellent</td>
        <td>Very fast. Native WebSockets.</td>
    </tr> <tr>
        <td>WinXP</td> <td>Firefox 3.0.19</td>
        <td>Good</td>
        <td>Some overhead from web-socket-js.</td>
    </tr> <tr>
        <td>WinXP</td> <td>Safari 5.0</td>
        <td>Fair</td>
        <td>Fast. Native WebSockets. Broken 'wss://' (SSL) - weird client header</td>
    </tr> <tr>
        <td>WinXP</td> <td>IE 6, 7, 8</td>
        <td><strong>Non-starter</strong></td>
        <td>No basic Canvas support. Javascript painfully slow.</td>
    </tr>
</table>


* Note 1: Opera interacts poorly with web-socket-js. After two
  disconnects the browser tab or Flash often hang. Although Javascript
  is faster than Firefox 3.5, the high variability of web-socket-js
  performance results in overall performance being lower. Middle mouse
  clicks and keyboard events need some work to work properly under
  Opera.


### Integration

The client is designed to be easily integrated with existing web
structure and style.

At a minimum you must include the `vnc.js` and `default_controls.js`
scripts and call their load() functions. For example:

    <head>
        <script src='include/vnc.js'></script>
        <script src="include/default_controls.js"></script>
    </head>
    <body>
        <div id='vnc'>Loading</div>
    </body>
    <script>
        window.onload = function () {
            DefaultControls.load('vnc');
            RFB.load(); };
    </script>

See `vnc.html` and `vnc_auto.html` for examples. The file
`include/plain.css` has a list of stylable elements.

The `vnc.js` also includes other scripts within the `include`
sub-directory. The `VNC_uri_prefix` variable can be use override the
URL path to the directory that contains the `include` sub-directory.


### Troubleshooting

You will need console logging support in the browser. Recent Chrome
and Opera versions have built in support. Firefox has a nice extension
called "firebug" that gives console logging support.

First, load the noVNC page with `logging=debug` added to the query string.
For example `vnc.html?logging=debug`.

Then, activate the console logger in your browser.  With Chrome it can
be activate using Ctrl+Shift+J and then switching to the "Console"
tab. With firefox+firebug, it can be activated using Ctrl+F12.

Now reproduce the problem. The console log output will give more
information about what is going wrong and where in the code the
problem is located. If you file a issue/bug, it can be very helpful to
copy the last page of console output leading up the problem into the
issue report.
