set_callback: set_callback

Description Usage Arguments Details Value Author(s) See Also Examples

View source: R/websockets.R

Description

Assign an R function to service an HTML 5 Websocket event type.

Usage

1
2
set_callback(id, f, envir)
setCallback(id, f, envir)

Arguments

id

The callback name. Presently supported names are closed, established, and receive.

f

The callback function. See the details section for required function arguments.

envir

The environment associated with the R websocket context returned by createContext.

Details

Define one or more of the callback functions to respond to websocket events (all of them are optional). A callback function is evaluated whenever a matching event is serviced by the service function. There are three supported callback function names: established, receive, and closed, that are evaluated when corresponding events occur for the websocket.

The receive function must take three arguments:

  1. DATA A RAW vector that holds any incoming data associated with the event, for example from broadcast or receive.

  2. WS The websocket file descriptor.

  3. HEADER Contains message header information for newer protocol messages. The vignette describes this parameter in detail. Although it is a required parameter, it is usually ignored in practice. The closed callback is fired whenever a websocket client socket is closed. The receive callback occurs when data is received on a client websocket. The established callback occurs when a new websocket client socket connection is successfully negotiated.

The established and closed functions must each take one argument:

  1. WS The websocket file descriptor.

. NOTE THAT THE CALLBACK FUNCTION PARAMETERS HAVE CHANGED AS OF PACKAGE VERSION 1.1.0 AND ARE NOT COMPATIBLE WITH PREVIOUS PACKAGE VERSIONS.

The arguments will be populated by data corresponding to the event. The WS socket can be used by the websocket_write function to write data to the client through the socket.

Non-websocket HTTP requests are serviced by the static function callback defined by the webpage argument described in the create_server help pages. The static function may also be redefined with set_callback.

Value

The set_callback function is invoked for its side effect of assigning the function to the variable name in the websocket context evnironment. NULL is invisible returned.

Author(s)

B. W. Lewis <[email protected]>

See Also

createContext create_server

Examples

1
# See the detailed example in help('websockets').

rstudio/R-Websockets documentation built on May 25, 2017, 8 p.m.