WebFund 2014W Lecture 6

2014-01-24T22:40:09Z

IlyA: Lecture 6 Notes

• Client-server
o Key distinction: Which ports they communicate on
o Web server means "I have a port listening on port 80"
• TCP/IP
o Port number: Identifies programs, 16 bit
• DNS
o Translating host-names to IP address
o When typing in an address, browser needs to do a DNS lookup to translate it to an IP address
• HTTP
o Modern browsers assume everything starts with "http://"
• HTML

• URL: Uniform Resource Locator
o Components
 Name of the server you wish to contact
 Resource you're requesting
• Server: A "box" to serve and deal with requests
• Internet: A network of other local networks, connecting them to each other
• Packets: 1500 bytes, switched networks, how computers send information to each other over a network
o Packet loss: When you're on a connection that loses too many packets, TCP cannot provide the illusion that you're on a continuous data stream
• IP address: source and destination both have one
o Can ping computers to find out their IP addresses and find the IP address of a server serving a webpage
o Identifies the computer to talk to
• When you're writing a web server, you're just writing a program that's running on a different port, and talking through TCP/IP
• express: a framework
o Difference between framework and middleware: Middleware is code that you can use; a framework is a way to organize your code, that may use middleware
• require: importing code from a directory to save time, instead of writing it yourself
o Looks for the file that was input as a parameter
• var user refers to ./routers/user, but it's not used so it doesn't do anything
• Web servers have infinite loops, in order to wait for events to come in so that they may handle it

WebFund 2014W Lecture 4

2014-01-20T18:20:41Z

IlyA:

The audio from the lecture given on January 17, 2014 is available [http://homeostasis.scs.carleton.ca/~soma/webfund-2014w/lectures/comp2406-2013f-lec04-17Jan2014.mp3 here].

'''Lecture 4'''

Assignment 1 Discussion

• Pieces of the code
o Node
o Jade
o HTTP
o Bootstrap
o jQuery
o HTML
• app.js
o JavaScript
• How do the other pieces fit?
o Look at the top, at the require lines
o Reference to the node's module system
 Searches for the directory indicated for an index.js file
 All loaded into variable you loaded it into (an 'exports' object is returned)
 Methods in the index.js beginning with "exports" are accessible by the var you loaded the object into
• When does app.js end?
o In the fraction of the second of when it's called
o Purpose of the file is to set up the page
o app.get and app.post
 Registered as callbacks since they run once and never again, but the functions that are registered ran everytime it's requested
 for app.get: if one parameter, you're accessing a field; 2 parameters and you're specifying a path
o app.use
 calls specific code from the parameter indicated
 path: directory name
 express.static
• apache; a static webserver; anything in the directory indicated can be accessed
o app.set
 sets a field in the app object specified in the first parameter, to whatever specified in the second parameter
o Ordering of lines in app.js is important
 e.g. having something loaded before loading the public folder's files tells node that the previous file takes precedence
• When rendering an object (res.render) for a response to a request, you pass in a jade template, and an object with fields (parameterizing the template)
• View engine: engine used as a template for HTMLs (e.g. 'jade')
o completely restricted access to server objects/variables due to security concerns; templates are isolated
o since we want to dynamically generate the page, we have to use a template
o some things we want to keep constant and not have to rerender all the time, and sometimes we want to change specific content
o makes it clear that we're not writing HTML, just a template that will be converted into an HTML document
• Spaces and tabs do not mix in jade. Use one only.
• Why do we need a different language for Jade?
o Domain-specific languages
 In Computer Science, a way to solve a problem is to create a language to solve it
 Makes things, previously complicated, easy
 CSS does not look like HTML, because it is a domain-specific language
 Compound languages: always language embedding
• Bootstrap
o Built off jQuery
o Runs on the client; completely in the browser
 allows you to dynamically change CSS to fit user's browser/screen (i.e. on the phone), less intensive on you (offloading a lot of work onto the browser)
 Major Reason: latency
• Everytime you make a request, to the server, it takes time an incredibly short time
• Annoying for the user to constantly wait for pages/response to actions
• Downloads webpages in the background; predicting what you will need soon in order to save time
o Allows you to grab an applet/webpage from another web server
 Cons: may not be always up, may send something different, usually done in faith, your application could break because of another web server that you don't have control over
o 2 portions: CSS (for styles), and JavaScript (code that makes it do things)
 JavaScript runs inside the browser (not yet ran something like this)

Soma-notes - User contributions [en]

WebFund 2014W Lecture 6

WebFund 2014W Lecture 4