Web servers for the Internet of ThingsSUMMER SCHOOL

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Outline

Web server

HTTP

Gadgets

IoT Webserver

Web templates

Web services

Web socket

Questions

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Web server

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What is a web server Software that implements HTTP/HTTPS

Mainframes

Computers

Gadgets

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Gadgets?!

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What HTTP? Widely used

Easy to implement

Text based

HTML◦ Simple and flexible UI◦ JavaScript runs in almost any browser◦ Replace displays

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UI Gadgets prefer HTML UI

Accessible from the tablet

Wireless “display”

Web language

Gadgets are using less displays

Expensive

Fixed

Special software

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HTTP

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HTTP

Image from https://www3.ntu.edu.sg/home/ehchua/programming/webprogramming/HTTP_Basics.html

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HTTP Request

◦ Headers◦ Method◦ URL◦ Query String◦ Upload body

Response◦ Status◦ Headers◦ Data

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Query http://address[:port]URL?querystring

http://wyliodrin.cs.pub.ro/projects?show=true

Address?

Port?

URL?

querystring?

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Query http://address[:port]URL?querystring

http://wyliodrin.cs.pub.ro/projects?show=true

Address? wyliodrin.cs.pub.ro

Port? 80

URL? /projects

querystring? show=true

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Methods GET

◦ Request objects without sending data

POST◦ Modify objects with data that you are sending

PUT◦ Create new objects with data that your are sending

DELETE◦ Delete objects without sending data

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HTTP

Image from https://www3.ntu.edu.sg/home/ehchua/programming/webprogramming/HTTP_Basics.html

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Gadgets

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Webserver for the gadgets

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Web Web request

◦ Starts a webserver◦ Sets up static folder◦ Stores

◦ Html◦ Javascript◦ Css

http://address:port/static/index.html

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Web Web request

◦ Route◦ Method◦ Port

Message

{

payload: query string / upload data

req: request

res: response

next:

}

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Web response Web response

◦ Input from a web request◦ Sends the payload◦ Redirect

http://address:port/ redirects to http://address:port/static/index.html

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Run the server Get the IP of the board

◦ Shell ◦ ifconfig

In the same network

http://172.17.0.82:5000/

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IoT Server

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IoT Server Server with public IP address

A gadget without pin access

Good for web server◦ Web pages◦ API

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IoT Server

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Web templates

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Web template Web template

◦ Loads a templates◦ Fills it with variables

◦ From value◦ From payload

◦ Sends it

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Web template• Values are available• Payload variables are available

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Web template

Value is refreshed only on a page reload

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Web service

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Web service is API Expose functions for apps

◦ Mobile Applications◦ Refresh the value without reloading the page◦ Use multiple UI

Image from http://blogs.msdn.com/b/martinkearn/archive/2015/01/05/introduction-to-rest-and-net-web-api.aspx

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Web response Web response

◦ Input from a web request◦ Sends the payload◦ Redirect

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Web response /sensor returns

{

“sensor”: “0”

}

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JQuery API

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Web socket

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Websocket Allows asynchronous communication with the server

◦ Like a socket◦ Uses HTTP or HTTPS◦ Problems with proxies

Socket.IO◦ Has a solution with HTTP or HTTPS if the websocket is unavailable

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Websocket

Image from https://warmcat.com/libwebsockets/2010/11/01/libwebsockets-html5-websocket-server-library-in-c.html

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Web starter app Streams

Web starter app

Angular JS

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Angular JS static/web.html

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Javascript

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Questions?