WebFund 2013F Lecture 7: Difference between revisions

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Revision as of 21:59, 8 November 2013

Audio from the lecture given on September 30, 2013 is available here.

Note

September 30

cookies
- text document
- saves info on what you were doing on site
stateless
- HTTPS
- SSH
what can server do to keep track of client?
- Cookies!
  - Something the server sets
  - sent along later
- Encode information in the url itself
  - that will say what this session identifier is
Server can't trust anything the client sends
webrequests are stateless
How to make sure the user doesn't mess with your cookies
- have to be encoded
  - cookies should look like garbage
  - if you can hand edit the cookie you are doing something really dumb
state is being passed around in url
remote procedure calls
- a program calling another and passing stuff around
- ie. like buttons on webpages
File:Http://homeostasis.scs.carleton.ca/wiki/index.php/File:Sept30.jpg
block
- running (on a 4 core processor you could have 4 processes running simultaneously)
- ready (waiting for a free processor)
- waiting on I/O (blocked until something has happened)
synchonous I/O
- read (b)
- what happens here?
  - Program went to sleep and is woken up
  - could be doing other things here instead of giving up the CPU!
  - Not efficient to switch between processes
- scanf(b)
  - only makes sense after read is completed
in node when you do any I/O code it returns immediately
- asynchronous
- callbacks solve asynchronous promblem
  - read(s, b, callback)
    - do the read request, and when it's done, here is the code to run encoded in this callback
node acts like a dispatcher
- constantly routing data
classic callback in node
- listen line
  - has a port number + callback function

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 Audio from the lecture given on September 30, 2013 is available [http://homeostasis.scs.carleton.ca/~soma/webfund-2013f/lectures/comp2406-2013f-lec07-30Sep2013.m4a here].
+==Note==
+September 30
+* cookies
+** text document
+** saves info on what you were doing on site
+* stateless
+** HTTPS
+** SSH
+* what can server do to keep track of client?
+** Cookies!
+*** Something the server sets
+*** sent along later
+** Encode information in the url itself
+*** that will say what this session identifier is
+* Server can't trust anything the client sends
+* webrequests are stateless
+* How to make sure the user doesn't mess with your cookies
+** have to be encoded
+*** cookies should look like garbage
+***if you can hand edit the cookie you are doing something really dumb
+* state is being passed around in url
+* remote procedure calls
+** a program calling another and passing stuff around
+** ie. like buttons on webpages
+* [[File:http://homeostasis.scs.carleton.ca/wiki/index.php/File:Sept30.jpg]]
+* block
+** running (on a 4 core processor you could have 4 processes running simultaneously)
+** ready (waiting for a free processor)
+** waiting on I/O (blocked until something has happened)
+* synchonous I/O
+** read (b)
+** what happens here?
+*** Program went to sleep and is woken up
+*** could be doing other things here instead of giving up the CPU!
+*** Not efficient to switch between processes
+** scanf(b)
+*** only makes sense after read is completed
+* in node when you do any I/O code it returns immediately
+** asynchronous
+** callbacks solve asynchronous promblem
+*** read(s, b, callback)
+**** do the read request, and when it's done, here is the code to run encoded in this callback
+* node acts like a dispatcher
+** constantly routing data
+* classic callback in node
+** listen line
+*** has a port number + callback function