Websocket

Question 1

What is WebSocket? And why do we need it?

Answer 1

WebSockets are a protocol built on top of TCP ( As HTTP for example) . They hold the connection to the server open so that the server can send information to the client, even in the absence of a request from the client. WebSockets allow for bi-directional, “full-duplex” communication between the client and the server by creating a persistent connection between the two.

Question 2

What is Connection?

Answer 2

A place for authorizing connection.

Question 3

What is Channel?

Answer 3

A place for common logic between channels.

Question 4

How to generate new channel?

Answer 4

rails g channel channel_name

Question 5

How to broadcast event?

Answer 5

ActionCable.server.broadcast “channel_name”, {}

Question 6

What files creates rails channel generator?

Answer 6

# app/channels/animals_channel.rb
class AnimalsChannel < ApplicationCable::Channel
  def subscribed
    # stream_from "some_channel"
  end

def unsubscribed
# Any cleanup needed when channel is unsubscribed
end
end

app/javascript/channels/animals_channel.js

consumer.subscriptions.create("AnimalsChannel", {
  connected() {
    // Called when the subscription is ready for use on the server
  },

  disconnected() {
    // Called when the subscription has been terminated by the server
  },

  received(data) {
    // Called when there's incoming data on the websocket for this channel
  }
});

Question 7

What files creates rails channel generator? ( 2 files and 5 methods)

Answer 7

# app/channels/animals_channel.rb
class AnimalsChannel < ApplicationCable::Channel
  def subscribed
    # stream_from "some_channel"
  end

def unsubscribed
# Any cleanup needed when channel is unsubscribed
end
end

app/javascript/channels/animals_channel.js

consumer.subscriptions.create("AnimalsChannel", {
  connected() {
    // Called when the subscription is ready for use on the server
  },

  disconnected() {
    // Called when the subscription has been terminated by the server
  },

  received(data) {
    // Called when there's incoming data on the websocket for this channel
  }
});

Question 8

How to create a stream subscription?

Answer 8

def subscribed
stream_from “sample”
end

Question 9

What are the main elements to create websocket event? ( 5 things)

Answer 9

1) Button
2) Action inside controller
3) Event which we run from action
4) A subscription that catch this event
5) JS that show the result on every page