How to use Postman to connect to Ruby on Rails 5 Actioncable (Websocket)?

Question

I am running a Rails 5.2.7 engine which has actioncable (websockets) set up. The websocket connection is successfully established when the application is run via the browser, using a React UI with actioncable-js-jwt, a version of actioncable's js package that supports jwt. However I am unable to establish the connection via postman's beta websockets option.

My connection.rb file is very simple:

module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    # Public: Invoked as part of the websocket connection establishment
    def connect
      self.current_user = {
        ...(hardcoded values)
      }
    end
  end
end

Engine.rb looks like this:

require 'action_cable/engine'

module RoundaboutEngine
  class << self
    def cable
      @cable ||= ActionCable::Server::Configuration.new
    end
  end

  class Engine < ::Rails::Engine
    isolate_namespace RoundaboutEngine

    class << self
      def server
        @server ||= ActionCable::Server::Base.new(config: RoundaboutEngine.cable)
      end
    end

    config.roundaboutengine_cable = RoundaboutEngine.cable
    config.roundaboutengine_cable.mount_path = '/cable'
    config.roundaboutengine_cable.connection_class = -> { RoundaboutEngine::Connection }
    config.roundaboutengine_cable.disable_request_forgery_protection = true

    initializer 'roundaboutengine_cable.cable.config' do
      RoundaboutEngine.cable.cable = { adapter: 'async' }
    end

    initializer 'roundaboutengine_cable.cable.logger' do
      RoundaboutEngine.cable.logger ||= ::Rails.logger
    end
  end
end

The browser request network tab shows the following:

Request URL: ws://localhost:9292/cable
Request Method: GET
Status Code: 101 Switching Protocols
Connection: Upgrade
Sec-WebSocket-Accept: [string]
Sec-WebSocket-Protocol: actioncable-v1-json
Upgrade: websocket

In postman, I also use ws://localhost:9292/cable as a raw connection. However, it seems to turn that into an http url, as shown in the request information:

Request URL: http://localhost:9292/cable
Request Method: GET
Status Code: 404 Not Found
Request Headers
Sec-WebSocket-Version: 13
Sec-WebSocket-Key: [string]
Connection: Upgrade
Upgrade: websocket
Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits
Host: localhost:9292

I am not sure why postman is turning the request into an http request, or how to make this work.

I also tried adding Sec-WebSocket-Protocol: actioncable-v1-json to the postman request headers, with no luck.

Answer 1

Resolved: I had to replace a line in engine.rb

I removed: config.roundaboutengine_cable.disable_request_forgery_protection = true

I added: config.action_cable.allowed_request_origins = [/http:\/\/*/, /https:\/\/*/, nil]

In particular, the nil was important for postman and is what was causing the problem.