|  |  |  | Cockpit Guide |  | 
|---|
| cockpit.js: Raw Channelscockpit.js: Raw Channels — Raw communication channels | 
At a low level Cockpit communicates with the system via messages passed
      through various channels. These are usually exposed via higher level APIs,
      such as the cockpit.spawn() function.
      It is rare to use raw channels directly.
channel = cockpit.channel(options)
This function creates a new channel for communication with the system.
      It returns a new channel object. The options argument is a
      plain object. At least the "payload" option is required, and
      based on the payload type, other options may be required.
| 
 | Set to  | 
| 
 | The host to open the channel to. If an alternate user or port is
          required it can be specified as  | 
| 
 | The payload type for the channel. Only specific payload types are supported. | 
| 
 | Set to  Set to  | 
The channel object returned has the following fields and methods and
      events. You should call the
      channel.close()
      method when done with the channel.
A valid channel will always be returned and the is ready to
      channel.send(). The channel may
      close shortly afterword due
      to a failure.
channel.send(data)
Send a message over the channel. The contents of the message depends on the
      payload type of the channel. If a binary channel, then data is expected
      to be an Array of bytes or a Uint8Array. If not binary,
      then the data will be converted to a string if not already a string.
channel.control(options)
Notify the channel to tune certain parameters on the fly. The options
      is a plain javascript object, and the contents depend on the "payload"
      of the channel.
One common operation is to set "command" to "done" in the
      options field. To indicate that no further messages will be sent through the channel.
promise = channel.wait([callback])
Returns a promise that is ready when the channel is ready, or fails if the
      client closes. If a callback is specified, it is attached to the promise. The
      promise will be rejected or resolved with the contents options passed to the
      channel.onready and
      channel.onclose events respectively.
In general it's not necessary to wait for the channel before starting to use the channel.
channel.close([options])
Close the channel.
If options is present it can be a plain javascript object
      containing additional channel close options to send to the peer. If closing for
      because of a problem, set the "problem" field to a
      problem code. If options
      is not an object it will be treated as a "problem".
The close event will fire. A channel can also be closed by a peer or if the underlying transport closes.
channel.addEventListener("message", function(event, data) { ... })
An event triggered when the channel receives a message. The message is
      passed as a string to the handler in the data. In the case of binary
      channels data is an Uint8Array or an Array
      of bytes if the former is not supported by the browser. The contents of
      the message depends on the payload type of the channel.
channel.addEventListener("control", function(event, options) { ... })
An event triggered when the channel receives an control message in the
      middle of the flow. One particular use is when the command is set to
      "done" then no further messages will be received in the channel.
      The exact form of these messages depend on the "payload" of the
      channel.
channel.addEventListener("ready", function(event, options) { ... })
An event triggered when the other end of the channel is ready to start processing messages. This indicates the channel is completely open. It is possible to start sending messages on the channel before this point.
channel.addEventListener("close", function(event, options) { ... })
An event triggered when the channel closes. This can happen either because channel.close() function was called, or if the peer closed the channel, or the underlying transport closes.
The options will contain various close information, including a
      "problem" field which will be set if the channel was closed because
      of a problem.
cockpit.transport.origin
The HTTP origin that is being used by the underlying channel transport. This is
      read-only, you should not assign a value. If the browser supports
      window.location.origin then this will be identical to that value.
cockpit.transport.host
The host that this transport is going to talk to by default. This is read-only, you should not assign a value. If the value is null that means that the transport has not been setup yet.
cockpit.transport.csrf_token
A cross site request forgery token for use with external channels. This becomes valid once the connection is properly established.
cockpit.transport.options
Initialization options received over the underlying channel transport. These will be empty until connection is properly established.
cockpit.transport.wait(callback)
Call the callback function once the underlying channel transport is initialized.
      This will start the initialization if not already in progress or completed. If the
      channel transport is already initialized, then callback will be called
      immediately.
In general it's not necessary to wait for the transport before starting to open channels.
cockpit.transport.close([problem])
Close the underlying channel transport. All channels open channels will close.
      The problem argument should be a problem code string. If not specified
      it will default to "disconnected".
cockpit.transport.filter(function(message, channelid, control) { ... }, [out])
Add a filter to the underlying channel transport. All incoming messages will be
      passed to each of the filter callbacks that are registered. If the out
      argument is equal to true then the filter will receive outgoing messages
      that being sent on the underlying channel transport.
This function is rarely used.
Filter callbacks are called in the order they are registered. If a filter
      callback returns false then the message will not be dispatched
      further, whether to other filters, or to channels, etc.
The message is the string or array with the raw message including,
      the framing. The channelid is the channel identifier or an empty string
      for control messages. If control is set then this is a control message,d
      and the control argument contains the parsed JSON object of the
      control message.
cockpit.transport.inject(message, [out])
Inject a message into the underlying channel transport. The message
      should be a string or an array of bytes, and should be valid
      according to the Cockpit message protocol. If the out argument is equal
      to false then the message will be injected as an incoming message as if
      it was received on the underlying channel transport.
This function is rarely used. In general you should only inject()
      messages you got from a filter().
string = cockpit.base64_encode(data)
Encode binary data into a string using the Base64 encoding. The data
      argument can either be a string, an Array, an ArrayBuffer
      or a Uint8Array. The return value is a string.
data = cockpit.base64_decode(string, [constructor])
Decode binary data from a Base64 encoded string. The string
      argument should be a javascript string. The returned data> will be an
      array of bytes.
You can pass Uint8Array, Array or String
      as an alternate constructor if you want the decoded data in an
      alternate form. The default is to return an Array. Note that if you use a
      String for the decoded data, then you must guarantee that the data
      does not contain bytes that would be invalid for a string.
encoder = cockpit.utf8_encoder([constructor])
Create an encoder for encoding a string into a UTF8 sequence of bytes.
You can pass Uint8Array, Array or String
      as an alternate constructor if you want the decoded data in an
      alternate form. The default is to return an Array.
data = encoder.encode(string)
Encode a string into a UTF8 sequence of bytes.
The resulting data is an array of bytes, but it's type may be
      modified by passing an alternate constructor to
      cockpit.utf8_encoder().
decoder = cockpit.utf8_decoder([fatal])
Creates a decoder to decode a UTF8 sequence of bytes data into a string.
If the fatal is set to true then the decoder
      will throw an exception when it encounters invalid UTF8 data. By default invalid data
      will be substituted with special UTF8 characters.
string = decoder.decode(data, [options])
Decode an array of UTF8 bytes into a string. The data
      argument may be an Array, a Uint8Array or a string containing
      binary data.
If options is passed it should be a plain javascript object. If
      options has a stream property equal to true,
      then multiple invocations of this function can be made with parts of the UTF8 sequence
      of bytes. Any trailing bytes that don't yet build a complete unicode character, will be
      cached until the next invocation. To drain the last data, call this function without
      the stream property set.