EpivizServer-class: Class providing WebSocket connection server

In epivizrServer: WebSocket server infrastructure for epivizr apps and packages

Description

Class providing WebSocket connection server

Details

The most important aspect of the API of this server are methods register_action and send_request. These are used to interact with the epiviz JS app through the provided websocket connection. register_action(action, callback) registers a callback function to be executed upon request from the epiviz JS app. When the server receives a JSON message through the websocket, it checks for an action field in the received request message, and then evaluates the expression callback(message_data) where message_data is obtained from the data field in the received message. A response will be sent to the epiviz app with field data populated with the result of the callback. If an error occurs during evaluation of the callback function, the response will be sent with field success set to false.

To send requests to the JS app, method send_request(request_data, callback) should be used. This is sends a request to the JS app with the data field populated with argument request_data. Once a response is received (with field success equal to true) the expression callback(response_data) is evaluated where response_data is obtained from the data field in the received response message.

Value

RC object with methods for communication with epiviz JS app

Methods

has_action(action)

Check if a callback is registered for given action<character>, <logical>. (See Details)

has_request_waiting()

Check if there is a sent request waiting for a response from JS app, <logical>

is_closed()

Check if server is closed, <logical>

is_daemonized()

Check if server is running in background, <logical>

is_interactive()

Check if server is running in interactive mode, <logical>

is_socket_connected()

Check if there is an open websocket connection to JS app, <logical>

register_action(action, callback)

Register a callback<function> to evaluate when epiviz JS sends a request for given action<character>. (See Details)

run_server(...)

Run server in blocking mode

send_request(request_data, callback)

Send request to epiviz JS app with given request_data<list>, and evaluate callback<function> when response arrives. (See Details)

service()

Listen to requests from server. Only has effect when non-daemonized

start_server()

Start the underlying httpuv server, daemonized if applicable

stop_server()

Stop the underlying httpuv server

stop_service()

Stop listenning to requests from server. Only has effect when non-daemonized.

unregister_action(action)

Unregister a callback function for given action<character> (if registered). (See Details)

wait_to_clear_requests(timeout = 3L)

Wait for timeout seconds to clear all pending requests.

Examples

server <- createServer()
server$register_action("getData", function(request_data) {
  list(x=1,y=3)
})

server$start_server()

server$send_request(list(x=2,y=5), function(response_data) {
  cat(response_data$x)
})

server$stop_server()

epivizrServer documentation built on Nov. 8, 2020, 11 p.m.