noVNC

noVNC API

The interface of the noVNC client consists of a single RFB object that is instantiated once per connection.

RFB

The RFB object represents a single connection to a VNC server. It communicates using a WebSocket that must provide a standard RFB protocol stream.

Constructor

RFB()

Creates and returns a new RFB object.

Properties

background

Is a valid CSS background style value indicating which background style should be applied to the element containing the remote session screen. The default value is rgb(40, 40, 40) (solid gray color).

capabilities Read only

Is an Object indicating which optional extensions are available on the server. Some methods may only be called if the corresponding capability is set. The following capabilities are defined:

name type description

power boolean Machine power control is available

name	type	description
`power`	`boolean`	Machine power control is available

clippingViewport Read only

Is a boolean indicating if the remote session is currently being clipped to its container. Only relevant if clipViewport is enabled.

clipViewport

Is a boolean indicating if the remote session should be clipped to its container. When disabled scrollbars will be shown to handle the resulting overflow. Disabled by default.

compressionLevel

Is an int in range [0-9] controlling the desired compression level. Value 0 means no compression. Level 1 uses a minimum of CPU resources and achieves weak compression ratios, while level 9 offers best compression but is slow in terms of CPU consumption on the server side. Use high levels with very slow network connections. Default value is 2.

dragViewport

Is a boolean indicating if mouse events should control the relative position of a clipped remote session. Only relevant if clipViewport is enabled. Disabled by default.

focusOnClick

Is a boolean indicating if keyboard focus should automatically be moved to the remote session when a mousedown or touchstart event is received. Enabled by default.

qualityLevel

Is an int in range [0-9] controlling the desired JPEG quality. Value 0 implies low quality and 9 implies high quality. Default value is 6.

resizeSession

Is a boolean indicating if a request to resize the remote session should be sent whenever the container changes dimensions. Disabled by default.

scaleViewport

Is a boolean indicating if the remote session should be scaled locally so it fits its container. When disabled it will be centered if the remote session is smaller than its container, or handled according to clipViewport if it is larger. Disabled by default.

showDotCursor

Is a boolean indicating whether a dot cursor should be shown instead of a zero-sized or fully-transparent cursor if the server sets such invisible cursor. Disabled by default.

viewOnly

Is a boolean indicating if any events (e.g. key presses or mouse movement) should be prevented from being sent to the server. Disabled by default.

Events

bell

The bell event is fired when a audible bell request is received from the server.

capabilities

The capabilities event is fired when RFB.capabilities is updated.

clipboard

The clipboard event is fired when clipboard data is received from the server.

clippingviewport

The clippingviewport event is fired when RFB.clippingViewport is updated.

connect

The connect event is fired when the RFB object has completed the connection and handshaking with the server.

credentialsrequired

The credentialsrequired event is fired when more credentials must be given to continue.

desktopname

The desktopname event is fired when the remote desktop name changes.

disconnect

The disconnect event is fired when the RFB object disconnects.

securityfailure

The securityfailure event is fired when the security negotiation with the server fails.

serververification

The serververification event is fired when the server identity must be confirmed by the user.

Methods

RFB.approveServer()

Proceed connecting to the server. Should be called after the serververification event has fired and the user has verified the identity of the server.

RFB.blur()

Remove keyboard focus from the remote session.

RFB.clipboardPasteFrom()

Send clipboard contents to server.

RFB.disconnect()

Disconnect from the server.

RFB.focus()

Move keyboard focus to the remote session.

RFB.getImageData()

Return the current content of the screen as an ImageData array.

RFB.machineReboot()

Request a reboot of the remote machine.

RFB.machineReset()

Request a reset of the remote machine.

RFB.machineShutdown()

Request a shutdown of the remote machine.

RFB.sendCredentials()

Send credentials to server. Should be called after the credentialsrequired event has fired.

RFB.sendCtrlAltDel()

Send Ctrl-Alt-Del key sequence.

RFB.sendKey()

Send a key event.

RFB.toBlob()

Return the current content of the screen as Blob encoded image file.

RFB.toDataURL()

Return the current content of the screen as data-url encoded image file.

Details

RFB()

The RFB() constructor returns a new RFB object and initiates a new connection to a specified VNC server.

Syntax

new RFB(target, urlOrChannel);
new RFB(target, urlOrChannel, options);

Parameters

target

A block HTMLElement that specifies where the RFB object should attach itself. The existing contents of the HTMLElement will be untouched, but new elements will be added during the lifetime of the RFB object.

urlOrChannel

A DOMString specifying the VNC server to connect to. This must be a valid WebSocket URL. This can also be a WebSocket or RTCDataChannel.

options Optional

An Object specifying extra details about how the connection should be made.

Possible options:

shared

A boolean indicating if the remote server should be shared or if any other connected clients should be disconnected. Enabled by default.

credentials

An Object specifying the credentials to provide to the server when authenticating. The following credentials are possible:

name	type	description
`"username"`	`DOMString`	The user that authenticates
`"password"`	`DOMString`	Password for the user
`"target"`	`DOMString`	Target machine or session

repeaterID

A DOMString specifying the ID to provide to any VNC repeater encountered.

wsProtocols

An Array of DOMStrings specifying the sub-protocols to use in the WebSocket connection. Empty by default.

bell

The bell event is fired when the server has requested an audible bell.

capabilities

The capabilities event is fired whenever an entry is added or removed from RFB.capabilities. The detail property is an Object with the property capabilities containing the new value of RFB.capabilities.

clippingviewport

The clippingviewport event is fired whenever RFB.clippingViewport changes between true and false. The detail property is a boolean with the new value of RFB.clippingViewport.

clipboard

The clipboard event is fired when the server has sent clipboard data. The detail property is an Object containing the property text which is a DOMString with the clipboard data.

credentialsrequired

The credentialsrequired event is fired when the server requests more credentials than were specified to RFB(). The detail property is an Object containing the property types which is an Array of DOMString listing the credentials that are required.

connect

The connect event is fired after all the handshaking with the server is completed and the connection is fully established. After this event the RFB object is ready to recieve graphics updates and to send input.

desktopname

The desktopname event is fired when the name of the remote desktop changes. The detail property is an Object with the property name which is a DOMString specifying the new name.

disconnect

The disconnect event is fired when the connection has been terminated. The detail property is an Object that contains the property clean. clean is a boolean indicating if the termination was clean or not. In the event of an unexpected termination or an error clean will be set to false.

securityfailure

The securityfailure event is fired when the handshaking process with the server fails during the security negotiation step. The detail property is an Object containing the following properties:

Property	Type	Description
`status`	`long`	The failure status code
`reason`	`DOMString`	The optional reason for the failure

The property status corresponds to the SecurityResult status code in cases of failure. A status of zero will not be sent in this event since that indicates a successful security handshaking process. The optional property reason is provided by the server and thus the language of the string is not known. However most servers will probably send English strings. The server can choose to not send a reason and in these cases the reason property will be omitted.

serververification

The serververification event is fired when the server provides information that allows the user to verify that it is the correct server and protect against a man-in-the-middle attack. The detail property is an Object containing the property type which is a DOMString specifying which type of information the server has provided. Other properties are also available, depending on the value of type:

"RSA"

The server identity is verified using just a RSA key. The property publickey is a Uint8Array containing the public key in a unsigned big endian representation.

RFB.approveServer()

The RFB.approveServer() method is used to signal that the user has verified the server identity provided in a serververification event and that the connection can continue.

Syntax

RFB.approveServer();

RFB.blur()

The RFB.blur() method remove keyboard focus on the remote session. Keyboard events will no longer be sent to the remote server after this point.

Syntax

RFB.blur();

RFB.clipboardPasteFrom()

The RFB.clipboardPasteFrom() method is used to send clipboard data to the remote server.

Syntax

RFB.clipboardPasteFrom(text);

Parameters

text

A DOMString specifying the clipboard data to send.

RFB.disconnect()

The RFB.disconnect() method is used to disconnect from the currently connected server.

Syntax

RFB.disconnect();

RFB.focus()

The RFB.focus() method sets the keyboard focus on the remote session. Keyboard events will be sent to the remote server after this point.

Syntax

RFB.focus();
RFB.focus(options);

Parameters

options Optional

A object providing options to control how the focus will be performed. Please see HTMLElement.focus() for available options.

RFB.getImageData()

The RFB.getImageData() method is used to return the current content of the screen encoded as ImageData.

Syntax

RFB.getImageData();

RFB.machineReboot()

The RFB.machineReboot() method is used to request a clean reboot of the remote machine. The capability power must be set for this method to have any effect.

Syntax

RFB.machineReboot();

RFB.machineReset()

The RFB.machineReset() method is used to request a forced reset of the remote machine. The capability power must be set for this method to have any effect.

Syntax

RFB.machineReset();

RFB.machineShutdown()

The RFB.machineShutdown() method is used to request to shut down the remote machine. The capability power must be set for this method to have any effect.

Syntax

RFB.machineShutdown();

RFB.sendCredentials()

The RFB.sendCredentials() method is used to provide the missing credentials after a credentialsrequired event has been fired.

Syntax

RFB.sendCredentials(credentials);

Parameters

credentials

An Object specifying the credentials to provide to the server when authenticating. See RFB() for details.

RFB.sendCtrlAltDel()

The RFB.sendCtrlAltDel() method is used to send the key sequence left Control, left Alt, Delete. This is a convenience wrapper around RFB.sendKey().

Syntax

RFB.sendCtrlAltDel();

RFB.sendKey()

The RFB.sendKey() method is used to send a key event to the server.

Syntax

RFB.sendKey(keysym, code);
RFB.sendKey(keysym, code, down);

Parameters

keysym

A long specifying the RFB keysym to send. Can be 0 if a valid code is specified.

code

A DOMString specifying the physical key to send. Valid values are those that can be specified to KeyboardEvent.code. If the physical key cannot be determined then null shall be specified.

down Optional

A boolean specifying if a press or a release event should be sent. If omitted then both a press and release event are sent.

RFB.toBlob()

The RFB.toBlob() method is used to return the current content of the screen encoded as Blob.

Syntax

RFB.toBlob(callback);
RFB.toBlob(callback, type);
RFB.toBlob(callback, type, quality);

Parameters

callback

A callback function which will receive the resulting Blob as the single argument

type Optional

A string indicating the requested MIME type of the image

quality Optional

A number between 0 and 1 indicating the image quality.

RFB.toDataURL()

The RFB.toDataURL() method is used to return the current content of the screen encoded as a data URL that could for example be put in the src attribute of an img tag.

Syntax

RFB.toDataURL();
RFB.toDataURL(type);
RFB.toDataURL(type, encoderOptions);

Parameters

type Optional

A string indicating the requested MIME type of the image

encoderOptions Optional

A number between 0 and 1 indicating the image quality.