subscribe websocket on backend

This block is part of the websocket group and was last modified in core v13.0.5.

subscribe websocket on backend execute_function v13.0.5

Subscribes the websocket to a specific channel. All broadcasts will be handled in the backend.

In pins 4 + flow

flow
channels array required
Multiple channels you would like the server to subscribe / listen on • Hidden when other fields are filled
channel value required
A channel you would like the server to subscribe / listen on • Hidden when other fields are filled
events array
Listen on the provided events. If you would like to listen on all events within this channel, leave this array empty or provide * as one of the values.
Default ["*"]
skip jwt condition required
Skips the broadcast of subscriptions to the frontend. If set to true, the frontend will not be able to resubscribe on the channels where the broadcast was skipped.
Default false

Out pins 4 + flow

flow
on broadcast execute_function
The callback function requested whenever we received any event on any of the given channels
success condition
Indicates if we could start subscribing at all, true could indicate we subscribed to one of the many given channels.
error value
channels array
Channels we succesfully subcribed to

Subscribes the current websocket connection to the given channels (the channels array, or the single channel value) and runs the function wired to on_broadcast for each incoming broadcast, passing its event and message. success=true only means the block ran with a callback and a websocket : it stays true even when ZERO channel subscriptions succeeded, so check the channels output for what actually subscribed. An empty channel list fails with MISSING_CHANNELS, no wired callback with MISSING_CALLBACK, no active websocket with MISSING_WEBSOCKET; in simulation it does nothing and errors PRODUCTION_RUN_ONLY. An empty events array listens to all events on the channel; skipjwt=true hides the subscription from the frontend.

A typical wiring for subscribe websocket on backend: a function trigger starts the flow; the function out pin wires to an execute block.

Version history

Introduced in v13.0.5.

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