Create a WebSocket client

Description

WebSocket$new(url,
  protocols = character(0),
  headers = NULL,
  autoConnect = TRUE,
  accessLogChannels = c("none"),
  errorLogChannels = NULL,
  maxMessageSize = 32 * 1024 * 1024)

Arguments

Details

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: Connecting

The WebSocket has not yet established a connection with the server.

1L: Open

The WebSocket has connected and can send and receive messages.

2L: Closing

The WebSocket is in the process of closing.

3L: Closed

The WebSocket has closed, or failed to open.

setAccessLogChannels(channels)

Enable the websocket Access channels after the websocket's creation. A value of NULL will not enable any new Access channels.

setErrorLogChannels(channels)

Enable the websocket Error channels after the websocket's creation. A value of NULL will not enable any new Error channels.

clearAccessLogChannels(channels)

Disable the websocket Access channels after the websocket's creation. A value of NULL will not clear any existing Access channels.

clearErrorLogChannels(channels)

Disable the websocket Error channels after the websocket's creation. A value of NULL will not clear any existing Error channels.

Examples

## 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.
}