ActionCable::Helpers::ActionCableHelper
Methods
A
Instance Public methods
action_cable_meta_tag()

Returns an “action-cable-url” meta tag with the value of the URL specified in your configuration. Ensure this is above your JavaScript tag:

<head>
  <%= action_cable_meta_tag %>
  <%= javascript_include_tag 'application', 'data-turbolinks-track' => 'reload' %>
</head>

This is then used by Action Cable to determine the URL of your WebSocket server. Your CoffeeScript can then connect to the server without needing to specify the URL directly:

#= require cable
@App = {}
App.cable = Cable.createConsumer()

Make sure to specify the correct server location in each of your environment config files:

config.action_cable.mount_path = "/cable123"
<%= action_cable_meta_tag %> would render:
=> <meta name="action-cable-url" content="/cable123" />

config.action_cable.url = "ws://actioncable.com"
<%= action_cable_meta_tag %> would render:
=> <meta name="action-cable-url" content="ws://actioncable.com" />

Source: show | on GitHub 

# File actioncable/lib/action_cable/helpers/action_cable_helper.rb, line 31
def action_cable_meta_tag
  tag "meta", name: "action-cable-url", content: (
    ActionCable.server.config.url ||
    ActionCable.server.config.mount_path ||
    raise("No Action Cable URL configured -- please configure this at config.action_cable.url")
  )
end