# Websockets

Web IDL: Web IDL is an interface description language (IDL) format for describing application programming interfaces (APIs) that are intended to be implemented in web browsers.
XHR - Xml HTTP Request: is an API, whose objects are provided by the browser's JavaScript environment.

# How to get realtime updates from server?

Short Polling
Long Polling - poll and then wait for sometime, until server sends response
Websockets - full duplex communication

Send HTTP GET request via telnet

telnet www.google.com 80
GET /

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: HSmrc0sMlYUkAGmm5OPpG2HaGWk=
Sec-WebSocket-Protocol: chat

# Websockets

HTTP is unidirectional, stateless

**ws**://www.google.com
**wss**://www.google.com

devtools inspect ws

Chrome -> devtools -> Netowrk tab -> WS

providing full-duplex communication channels over a single TCP connection
being standardize by W3C in Web IDL
works at Layer 7 in OSI model
2 parts
- Handshake to establish connection
  - Uses HTTP upgraer header
- then actual data transfer
- similar to network MAC Protocols, CSMA/CA
Nginx has supported WebSockets since 2013
Masks data from other connections

WARNING

WebSocket servers must validate the "Origin" header against the expected origins during connection establishment, to avoid Cross-Site WebSocket Hijacking attacks

Works in 3 stages

Opening Handshake
Data Exchange
Close Connection

# Where and when websockets can be used?

feeds are updated in realtime by websockets

Gaming Applications
Chat Applications
Realtime online crypto exchanges
- pro.coinbase.com
Social feeds
Collaborative editing/coding
SPorts update

# Beginners Guide to Websockets

upgrade to HTTP

How fast are they over traditional HTTP
Transport Layer
- TCP, UDP
Internet Layer
- IPv6, IPv4
Application Layer
- HTTP, Websocket, SSL, IMAP, POP
Meet AJAX
How to implement it?
Browser Support
cannot communicate with REST

SocketIO is to websocket what jQuery is to Javascript

Dion Misic

namespaces
fail backs

Polling
Long Polling, keep connection open until new data has arrived
Server Sent Events
1. Event source API
2. not truly bi-directional
3. need a event loop
4. works well with existing APIs

# Websockets vs AJAX

# HTTP 2

Decrease latency to improve page load speed in web browsers by considering:
data compression of HTTP headers
HTTP/2 Server Push
pipelining of requests
fixing the head-of-line blocking problem in HTTP 1.x
multiplexing multiple requests over a single TCP connection

HTTP handhsake sequence diagram

# How is it websocket different from HTTP?

# How does HTTP work?

connection is opened and closed by server

# Make realtime application that updates data from server?

Browserstack
pro.coinbase
financial exchanges
realtime news/social feeds
realtime chat
uber - watch cars moving

# How to implement and use WS?

# .NET Framework

Signal IR library
we recommend SignalR over raw WebSockets
- SignalR provides transport fallback for environments where WebSockets is not available
A variable which holds socket connection, initialized on document load
Sysnchronous vs Asynchronous principles
HTTP, XMLHTTPRequest and websockets concepts
Websocket API
- Methods
  - send
  - close
- Events
  - open
  - Message
  - Error
  - close
How SignalR library works internally

# Socket Programming | Nettwork Programming

To build any networked application, we need socket Programming

Basics of TCP/IP Protocol connection
What and how do we program a connection?
Client Server Model
What are requests and response?
Which program generates them?

# Berkley's Socket API

What are [Socket]? to be specific Berkley Sockets
Are GPC different from sockets?
- Yes, RPC are meant for OS whereas sockets are for communication b/w computers over the network

Good Questions

How does traditional HTTP protocol works?
How did AJAX changed it?
What do websockets offer? and at what cost?

Socket

# Resources

← Web perfromance