Socket.io communication in detail

1. Hao-kang Den @_hden
Socket.io under the hood

3. Agenda
● Why socket.io?
● What’s socket.io? What’s websocket?
● Socket.io in detail

4. HTTP
serverclient
(1) request
(2) response
WTF?
X

5. Bi-directional Communication
serverclient
(1) signal
(2) acknowledgement
(3) signal
(4) acknowledgement

6. Why don’t we use websocket?
● Standardized by
○ RFC 6455
○ W3C
● IE9 says NO

7. Why socket.io?
+ native iOS & Android

8. Socket.io Communication Layers
API
packet
communication (ws, jsonp, etc.)

10. API
# client
socket.emit(‘foo’, param1, param2, ...)
socket.on ‘bar’, (param1, param2, ...) ->
console.log(‘yay got a bar!’)
# server
socket.on ‘foo’, (param1, param2, ...) ->
console.log(‘yay got a foo!’)
socket.emit(‘bar’, param1, param2, ...)

11. Packet
socket.emit(‘foo’, param1, param2, ...)
# socket.io v0.9.x
packet = {
type: ‘event’
id: ‘unique packet id’
name: ‘foo’
args: [param1, param2, ...]
}
# socket.io v1.0.x
packet = {
type: ‘event’
id: ‘unique packet id’
name: ‘foo’
data: [param1, param2, ...]
}
https://github.com/LearnBoost/socket.io-protocol

12. Communication Layer
# socket.io v0.9.x
packet = {
type: ‘event’
id: 1
name: ‘foo’
args: [param1, param2, ...]
}
# socket.io v0.9.x
5:1::{“name”:”foo”,”args”:[param1, param2, ...]}
https://github.com/LearnBoost/socket.io-spec

13. Further Reading
● http://davidwalsh.name/websocket
● test/spec https://github.com/LearnBoost/socket.io/blob/master/test/socket.io.js
● code https://github.com/LearnBoost/socket.io/blob/master/lib/socket.js
read!