WebSocket$new(url, protocols = character(0), headers = NULL, autoConnect = TRUE, accessLogChannels = c("none"), errorLogChannels = NULL, maxMessageSize = 32 * 1024 * 1024)
url | The WebSocket URL. Should begin with |
---|---|
protocols | Zero or more WebSocket sub-protocol names to offer to the server during the opening handshake. |
headers | A named list or character vector representing keys and values of headers in the initial HTTP request. |
autoConnect | If set to `FALSE`, then constructing the WebSocket object will not automatically cause the connection to be established. This can be used if control will return to R before event handlers can be set on the WebSocket object (i.e. you are constructing a WebSocket object manually at an interactive R console); after you are done attaching event handlers, you must call `ws$connect()` to establish the WebSocket connection. |
accessLogChannels | A character vector of access log channels that are
enabled. Defaults to A few commonly used access logging values are:
All logging levels are explained in more detail at https://docs.websocketpp.org/reference_8logging.html. |
errorLogChannels | A character vector of error log channels that are
displayed. The default value is A few commonly used error logging values are:
All logging levels are explained in more detail at https://docs.websocketpp.org/reference_8logging.html. |
maxMessageSize | The maximum size of a message in bytes. If a message
larger than this is sent, the connection will fail with the |
A WebSocket object has four events you can listen for, by calling the corresponding `onXXX` method and passing it a callback function. All callback functions must take a single `event` argument. The `event` argument is a named list that always contains a `target` element that is the WebSocket object that originated the event, plus any other relevant data as detailed below.
onMessage
Called each time a message is received from the server. The event will have a `data` element, which is the message content. If the message is text, the `data` will be a one-element character vector; if the message is binary, it will be a raw vector.
onOpen
Called when the connection is established.
onClose
Called when a previously-opened connection is closed. The event will have `code` (integer) and `reason` (one-element character) elements that describe the remote's reason for closing.
onError
Called when the connection fails to be established. The event will have an `message` element, a character vector of length 1 describing the reason for the error.
Each `onXXX` method can be called multiple times to register multiple callbacks. Each time an `onXXX` is called, its (invisible) return value is a function that can be invoked to cancel that particular registration.
A WebSocket object also has the following methods:
connect()
Initiates the connection to the server. (This does not need to be called unless you have passed `autoConnect=FALSE` to the constructor.)
send(msg)
Sends a message to the server.
close()
Closes the connection.
readyState()
Returns an integer representing the state of the connection.
0L
: ConnectingThe WebSocket has not yet established a connection with the server.
1L
: OpenThe WebSocket has connected and can send and receive messages.
2L
: ClosingThe WebSocket is in the process of closing.
3L
: ClosedThe WebSocket has closed, or failed to open.
Enable the websocket Access channels after the
websocket's creation. A value of NULL
will not enable any new Access channels.
Enable the websocket Error channels after the
websocket's creation. A value of NULL
will not enable any new Error channels.
Disable the websocket Access channels after the
websocket's creation. A value of NULL
will not clear any existing Access channels.
Disable the websocket Error channels after the
websocket's creation. A value of NULL
will not clear any existing Error channels.
## Only run this example in interactive R sessions if (interactive()) { # Create a websocket using the websocket.org test server ws <- WebSocket$new("ws://echo.websocket.org/") ws$onMessage(function(event) { cat("Client got msg:", event$data, "\n") }) ws$onClose(function(event) { cat("Client disconnected\n") }) ws$onOpen(function(event) { cat("Client connected\n") }) # Try sending a message with ws$send("hello"). # Close the websocket with ws$close() after you're done with it. }