Serverside Technology

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Serverside Technology

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data with a remote active socket. The Berkeley Socket API ... Pronounce 'Sequel' Information Retrieval. Information Modification. Information Definition ... – PowerPoint PPT presentation

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Title: Serverside Technology

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Serverside Technology

Transport Server
BSD Sockets
Dynamic Webserver
Serverside Scripting, CMS
Multitier Webserver
Database Intro, SQL, GoogleAE

3
Transport Server
4
Remember Ports

lookup table
216 entries per host
each packet has
a destination port

5
Ports

Defaults
smtp is 25

6
Services and Ports

Server applications wait
for incoming connections
or packets

7
Berkeley Sockets

(bad) metaphore for digital connections
passive sockets wait for requests
active sockets exchange
data with a remote active socket

8
The Berkeley Socket API

The most common transport-layer interface
low-level
connect and disconnect sockets
send and receive data over a socket
connectionless and connection-oriented

9
Socket Programming Interface

socket create a new socket
bind bind to a local TCP/IP port
listen allow incoming data on a port
accept wait for data to arrive
select wait for data on multiple sockets
connect connect to a remote TCP/IP port
send transmit data
recv receive data (if any)?
close close an existing socket

10
socket()

create a socket
choose a transportation
mode

?
11
server bind()

occupy a port
as passive socket
if not already taken!

12
server listen()

start accepting
clients

13
client connect()

'walk up to a desk'
i.e., select a port
ask to open a connection
if connection-oriented

14
server accept()

wait a single
connection request
only if connection-oriented
creates a new active socket on the server to
handle the request.

Now a connection
is established
Both sides have
an active socket

16
send() and recv()
17
send() and recv()
18
close()
19
Simple Server 1/2

import socket
import sys
create a socket
s socket.socket(socket.AF_INET,
socket.SOCK_STREAM)?
associate the socket with a hostport
combination
hostname can be empty on the serverside
s.bind((, 80))?

20
Simple Server 2/2

s.listen(1)?
conn, addr s.accept()?
print client is at, addr
read string from client
data conn.recv(???)?
conn.send(HTTP/1.0 200 OK ...)?
conn.close()?

21
Assignment 1.b Hint

The telnet protocol is simpler, but similar
Search for examples online!

22
Serverside Technology

Transport Server
BSD Sockets
Dynamic Webserver
Serverside Scripting, CMS
Multitier Webserver
Database Intro, SQL, GoogleAE

23
Transport Server Programming
Application Server Programming
24
Application Server Programming

Purpose
templates, data-driven web, cms
Overview
Tools
Programming

25
Scripting 1 Templates

Reuse HTML Code
Within a page
Throughout a site
Consistency
Rapid Development

26
Scripting 2 Data-driven webpages
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Scripting 2 Data-driven webpages
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Scripting 2 Data-driven webpages
29
Scripting 3 CMS

Web-driven data management
Content Management System
Frontend and Backend processing
Foolproof, location-independent

30
Scripting 3 CMS
31
Scripting 3 CMS
32
Application Server

Webserver
Application (in Python, PHP, ...)
Standard scripts
Storage (Files, Database)?
A CMS is an example of a web application server
another would be an e-commerce site

33
Application Server Programming

Purpose
Overview
Tools
Programming

34
Dynamic Document Generation

Combine static HTML
and
dynamic data
to create a page
on demand
i.e., when a request comes in

35
Simplified examples

templates file.read()
worldclock time.ctime()
wiki socket.read()

36
Many Serverside Languages

CGI
PHP
Python
Coldfusion
Java JSP and Servlets
MS Appliation Server Pages (ASP)?

37
Two Broad Approaches

Code inlining
vs.
Page generation

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Code Inlining
lthtmlgtltheadgtlttitlegtClockgtlt/titlegtlt/headgt ltbodygt ltp
gt The current time is lt?php echo
date('his') ?gt lt/pgt lt/bodygt lt/htmlgt

examples PHP, Java Server Pages, ASP

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Page Generation
import time socket.write('''lthtmlgtltheadgtlttitlegtCl
ockgtlt/titlegtlt/headgt ltbodygt ltpgt The current time
is ''' time.ctime() ''' lt/bodygt lt/htmlgt''')
examples Python, CGI/Perl, Java Servlets
40
Application Server Programming

Purpose
Overview
Tools
Sessions, Cookies, Authentication
Programming

41
Revisiting Sessions
42
Revisiting Sessions
43
Revisiting Cookies

Server sends data to Client
Client sends data in each request to Server
If server changes operation based on data
and changes data ...
... no longer stateless

44
Cookie implementation

GET /index.html HTTP/1.1
Host www.example.org
HTTP/1.1 200 OK
Content-type text/html
Set-Cookie namevalue
(content of page)
GET /spec.html HTTP/1.1
Host www.example.org
Cookie namevalue
Accept /

Client
Server
Client
45
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Cookie expiration

Server can set an expiration date
to save cookies across sessions
Otherwise cookies are removed
when the browser closes
Set-Cookie keyvalue expiresFri, 31-Dec-2010
235959 GMT

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Cookie Scope

Server can expand scope beyond single URL
Scope governed by (key, domain, path)
Set-Cookie keyvalue expiresFri, 31-Dec-2010
235959 GMT path/ domainjustthetext.appspot.c
om

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Cookie details

maximally 4 kB per cookie
at least 20 per domain allowed
case insensitive

49
Exercise Cookies and Sessions

Write an application that prints a counter
that increases each time a user visits the server

50
Authentication

User roles
Don't use HTTP Authentication
Encrypted transport and Forms
(We'll skip https)

51
Application Server Programming

Purpose
Overview
Tools
Programming

52
Template Generation

longname Homepage
shortname index
head open("header.html", "r")
body open(shortname ".contents.html", "r")
print "lthtmlgtltheadgtlttitlegt" longname
"lt/titlegtlt/headgtltbodygt"
print head.read()
print body.read()
head.close()
body.close()
OK. Return HTTP Code 200 (OK)
return 200

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Data-driven webpages

import BaseHTTPServer
class myhandler(BaseHTTPServer.BaseHTTPRequestHand
ler)
def do_GET(self)
self.send_response(200)
self.send_header("Content-
type", "text/html")
self.end_headers()
self.wfile.write("lthtmlgtlth
eadgtlttitlegtReslt/titlegtlt/headgt")
self.wfile.write("ltbodygtlth
1gtForm Resultslt/h1gtltpgt")
self.wfile.write(self.path
)
self.wfile.write("lt/pgtlt/bo
dygtlt/htmlgt")
port 8000
server BaseHTTPServer.HTTPServer(("", port),
myhandler)
print "Serving data from port " str(port)
server.serve_forever()

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Content Management System

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Serverside Technology

Transport Server
BSD Sockets
Dynamic Webserver
Serverside Scripting, CMS
Multitier Webserver
Database Intro, SQL, GoogleAE

56
For the exam, remember the function and
organizationof databasesnot the SQL syntax
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Persistent Storage

Needed for real applications
HTTP is stateless
Transferring large cookies?
slow
can be manipulated by user

58
Separation of Concerns

Presentation
Application Logic
Data Storage
For clarity/reuse as well as load balancing

59
Multi-tier Servers

Presentation (browser)?
Application (appserver)?
Storage (database)?
Compare Model-View-Controller

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Databases

Can store data more efficienty (space/time)?
Can retrieve data more intelligently
Topic of another class

61
Relational Databases

Combine multiple sets of data
Example ...

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Example
Students
Courses
Grades
The grade list is a relation of students and
courses
The grade list is a relation of students and
courses
63
SQL

Pronounce Sequel
Information Retrieval
Information Modification
Information Definition
statements are case insensitive
(but value strings aren't)

64
Information Retrieval

Select something
From somewhere
Where some constraints hold

65
Example

Select name
From students

66
Example constraints

Select year
From students
Where name 'Alice'

67
Example relationships

Select s.name, s.year
From students s, grades g
Where s.name g.student
and
g.grade lt 5

68
Example order

Select s.name, s.year
From students s, grades g
Where s.name g.student
and
g.grade lt 6
Order by s.name ASC

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Note on relationships

student.name and g.student both hold willem
might become inconsistent (e.g., address)
better is to add unique IDs
students (id, name, year, address)
and point to IDs
grades(student, course)

70
Example

Select s.name, s.year
From students s, grades g
Where s.name g.student
and
g.grade lt 6

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Data Modification Language (DML)?

INSERT
INSERT INTO students VALUES (willem, 1997)
UPDATE
UPDATE grades SET grade10 WHERE
studentWillem
DELETE
DELETE FROM courses WHERE studentWillem

72
Data Definition Language (DDL)?

CREATE TABLE
CREATE TABLE dropouts (name varchar(255), year
int)
DROP TABLE
DROP TABLE dropouts

73
A lot more to say on this topic

Separate course

74
Serverside Technology

Transport Server
BSD Sockets
Dynamic Webserver
Serverside Scripting, CMS
Multitier Webserver
Database Intro, SQL, GoogleAE

75
The remainder of this talk is practical
support,not exam material
76
Google App Engine

Server Basics
GAE Overview
GAE Use

77
First a python webserver

import BaseHTTPRequest
two classes
HTTPServer
BaseHTTPRequestHandler

NB This was assignment 1.b optional code is now
available from data/python/webserver.py
78
First a python webserver

override the requesthandler's methods
do_GET(self)
do_POST(self)
write output not using print, but using
self.wfile.write()

79
Exercises

Using webserver.py, build a
Clock page that tells the time
Counter page that increases a per-user counter
use cookies
NB I DID NOT EXPLAIN THIS IN CLASS
SEE NEW NEXT 2 SLIDES
Multiple pages clock and counter

80
Writing Cookies

Set a cookie by adding a self.send_header() call
to do_GET
Each call adds an HTTP header to the response
Make sure the header matches the Cookie syntax
(shown for instance on slide 45)
NB there is now a file cookie.py in
Internet Programming 2009\data\python

81
Reading Cookies

Read a cookie using module Cookie
Have python extract the HTTP request cookies as
string
cookiesstring self.headers.get('Cookie')
If there are cookies, have them parsed into a
dictionary using
cookies Cookie.SimpleCookie(cookiesstring)
mycookie will be a string (if the cookie
exists)

82
A template-driven website

Instead of writing plain text (or markup)
read file contents
Revisit slideset 3, with a file example
headerfile open(header.html, r)
headerdata headerfile.readlines()
self.wfile.write(headerdata)
headerfile.close()

code is available from data/python/template.py
83
Exercises

Using webserver.py and template.py,
build a minimal template driven website
then
convert your static website into a template
driven version

84
Working forms

requires parsing the URL encoded parameters
http//www.google.com.gh/search?qgoogleappengin
eurlparseieutf-8oeutf-8aqtrlscom.ubuntue
n-USunofficialclientfirefox-a
Not simple in Movable IDLE
because of older Python version (2.4)
Will defer until we move to GAE

85
Google App Engine

Server Basics
GAE Overview
GAE Use

86
Google App Engine
87
What is Google App Engine?

Google App Engine lets you run your web
applications on Google's infrastructure. App
Engine applications are easy to build, easy to
maintain, and easy to scale as your traffic and
data storage needs grow. With App Engine, there
are no servers to maintain You just upload your
application, and it's ready to serve your users.

code.google.com/appengine/docs/whatisgoogleappengi
ne.html
88
Cloud Computing
Your Program
Python
89
What is Google App Engine?

Google App Engine lets you run your web
applications on Google's infrastructure. App
Engine applications are easy to build, easy to
maintain, and easy to scale as your traffic and
data storage needs grow. With App Engine, there
are no servers to maintain You just upload your
application, and it's ready to serve your users.

code.google.com/appengine/docs/whatisgoogleappengi
ne.html
90
Cloud Computing

A form of hosting
Pro
Scalable
Fault tolerant
Vendor APIs
Low (maintenance) cost
Against
Data privacy concerns
Vendor Lock-in

en.wikipedia.org/wiki/Cloud_computing
91
Cloud Computing Providers

Amazon Web Services
low-level services storage, computation
Google App Engine
high-level services image manipulation
Others (HP, Microsoft) are preparing offerings

92
Documentation

code.google.com/appengine/docs
overview
tutorial
reference
FAQ
articles
samples
....

USE IT!
93
GAE Restrictions

Sandbox
No file access
Limited amount of work
No full SQL, but 'Google Query Language'

94
Persistent Storage

Google Query Language (QGL)
Similar to SQL, but restricted
no concept of tables or relationships
i.e., no select from a, b
only test for inequality on one property
if sorting must sort on this property first
(huh?)

95
Google App Engine

Server Basics
GAE Overview
GAE Use

96
Again, all that comes is explained in more
detailatcode.google.com/appengine/docs
97
Step 1 Sign up

Get a google account

98
Step 2 Register Project

99
Step 2 Register Project
100
Step 2 Register Project

Google will send you an SMS on your first project
If you don't want this, use my account instead

101
Step 3 Install Python

why?

102
Create Project

In Internet Programming 2009\python\google_appengi
ne
create subdirectory for your project
in Internet Programming 2009\python\google_appengi
ne\ltprojectgt
create file app.yaml
application ltprojectgt
version 1
runtime python
api_version 1
handlers
- url /.
script helloworld.py

103
helloworld.py
print 'Content-Type text/plain' print '' print
'Hello, world!'

next, change it to output a valid html page

104
Step 4 Development server

Runs locally, at port 8080
Start using
run_project.bat in google_appengine
copy to run_ltmyprojectgt.bat) and edit

105
Step 4 Development server

shared!
keep private backup of your files

106
Putting your website online

modify app.yaml to serve static files from
...\ltprojectgt\staticfiles
application ltprojectgt
version 1
runtime python
api_version 1
handlers
- url /staticfiles
static_dir staticfiles
- url /.
script helloworld.py

107
Putting your website online

create directory ...\ltprojectgt\staticfiles
copy all your static files into this directory
verify that they show up on the development
webserver
if you're happy, upload to your domain at
ltprojectgt.appspot.com

108
Step 5 Upload website

Test locally and upload when there are no bugs
Can overwrite previous versions
Use
appcfg.py --emailltgoogleemailgt update ltprojectgt
Better
copy to upload_project.bat and edit
more info code.google.com/appengine/docs/appcfgpy
.html

109
A slightly different webserver

No BaseHTTPServer.HTTPServer,
but webapp.WSGIApplication
Concept is the same create a server object,
which
will call your handler objects
Difference individual objects for individual
files

more info at http//code.google.com/appengine/docs
/webapp/running.html
110
Webserver code in your app

from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import
run_wsgi_app
application webapp.WSGIApplication(('/',
MainPage),
('/contact', Contact),
('/editentry', EditEntry),
('/deleteentry', DeleteEntry),
,
debugTrue)
def main()
run_wsgi_app(application)

111
Mapping requests to handlers

You attach a path to a handler ('/', MainPage)
Can attach multiple paths to the same handler
('/', MainPage), ('/other', MainPage)
and find out which path used in the object

112
Writing a requesthandler
class myreqhandler(webapp.RequestHandler) def
get(self) self.response.out.write("lthtmlgtltbody
gtltpgtHi there!lt/pgtlt/bodygtlt/htmlgt")

can override get, post, ... methods
can generate output using self.response.out.write
can inspect request using self.request
code.google.com/appengine/docs/webapp/requesthandl
ers.html
code.google.com/appengine/docs/webapp/requesthandl
erclass.html

113
Accessing request data

value request.get(key)
class myreqhandler(webapp.RequestHandler)
def get(self)
self.response.out.write("lthtmlgtltbodygtltpgtHi )
self.response.out.write(self.request.get(name
))
self.response.out.write(lt/pgtlt/bodygtlt/htmlgt")
code.google.com/appengine/docs/webapp/requesthandl
erclass.html

114
Forms

Read form results using request.get(ltkeygt)
code.google.com/appengine/docs/gettingstarted/hand
lingforms.html

115
Mapping requests to handlers (2)

Can also map unlimited paths at once
(r'/browse/(.)/(.)', BrowseHandler)

Wildcard arbitrary item
Seen by Browsehandler as arguments class
BrowseHandler(webapp.RequestHandler) def
get(self, category, product_id)
116
Templates