CODEWITHSUNDEEP
ruby-on-railsrubysocketshttprack
chailong
chailong

Reputation: 326

What is socket hijacking?

I'm reading a great post on Rails 5 actioncable introduction. There it says: "Action Cable uses the Rack socket hijacking API to take over control of connections from the application server. ". What does the "socket hijacking" mean?

Upvotes: 3

Views: 3001

Answers (1)

Luka Kerr
Luka Kerr

Reputation: 4239

Socket Hijacking was implemented with rack 1.5.0 - a modular Ruby webserver interface.

Rack 1.5.0 basically provides a simple and adaptable interface for developing apps in rails. It does this by wrapping HTTP requests and their responses in a simply way. It also combines the API's for web servers, web frameworks, and middleware into a single method call.

So, in rack 1.5.0 socket hijacking is used to allow rails apps to overtake the client socket and perform other operations on it. These operations include:

  • Implementing WebSockets
  • Streaming data
  • Other interactivity between user's browser and server

WebSockets allows the user to send messages to a server and receive event driven responses without having to poll the server for a reply.

This is shown in this diagram - as you can see, once the WebSocket connection is opened, messages can be sent and received between the user and server.

WebSockets

Anyway, in the Rack Socket Hijacking API that you specified, it essentially provides two modes:

  • Full hijacking API

    • This gives the app complete control over what goes over the socket. The app server doesn’t send anything over the socket, and lets the app take care of it.

  • Partial hijacking API

    • This gives the app control over the socket after the app server has already sent out headers. This mode is basically used for streaming.

So - In the end, socket hijacking basically allows ruby/rails apps to override/overtake a client socket and carry out different functions on it, or as you wrote - take control of connections from the application server.

Upvotes: 6

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