BIT3283 (1) INTRO -Client Server Programming 230911_001

8/3/2019 BIT3283 (1) INTRO -Client Server Programming 230911_001

1/57

FSKTMFIND YOUR VOICE AND INSPIRE OTHERS

Client Server Programming

(BIT 3283 / BIT32803)


2/57

5/5/2012 Client Server Programming 2

Concepts

Standalone (Single User)

Host Centric (Multi User)

Client/ServerNetwork Operating System

Middleware

Application Layering


3/57

Standalone (Single User)


4/57


Standalone Single User

Application and Data reside on the same computer

Dedicated for single user

Powerful and economical

Examples: Calculator, MS Word, etc.


5/57

Host Centric (Multi User)


6/57


Host Centric Multi UserHost Centric approach

Applications and data components reside and execute on onecentralized platform

Multiple users access the same application on this central platform

Example : mainframe

Proprietary Technology

Host Centric Approach


7/57

Presentation Logic

ApplicationLogic

DBMS

Client

Server

Network

Client (dumb) - Server Model


8/57

Client/Server


9/57


Client/Server Technology

Client/server technology involves the client and server,both having processing capabilities.

The client request for a service and the server processesthis request and sends a reply.


10/57

True Client-Server Model

Presentation Logic

Client

Server

Network

Application Logic

DBMS


11/57

Distributed Client-Server Model

Client

Server

Network

Application Logic

DBMS

Application Logic

Presentation Logic


12/57

Client-server computing is

distributed access, not adistributed computing.


13/57


Types of services provided by different servers

File ServersGroupware Servers e.g. Lotus Domino

Mail Servers

Newsgroup ServersCalendar Servers

Workflow Servers

Database ServersTransaction Servers


14/57


File Server In this case, all the files are stored in a central place called file

server The entire file is passed to the client over a network

These type of servers are useful for creating a repository for images,flat documents, and drawings.


15/57


Groupware Servers

Groupware Servers are software designed to provideservices to a workgroup

Workgroup is a group of people working on a commontask

Usually groupware servers handle semi-structuredinformation unlike databases or files

Groupware is used to Communicate, Collaborate, andCoordinate among teams Allow access to the same data

Manages concurrency Everyone in the group can work on the same resource

Improves efficiency of teams


16/57


Groupware Servers Email Services E-Mail: Messages that are sent electronically via computer networks

A mail server provides e-mail services to computers on a network Mail can be accessed using E-mail clients Mail service can also be used by business application as well Example: when you apply for leave, a mail is sent to the approving manager by

the leave system

A mail client uses POP3 or IMAP4 protocol to connect to a Mail server Mail client uses LDAP protocol to access the e-mail address book


17/57


? POP3 (http://www.learnthat.com/define/view.asp?id=6712)

POP3 Definition Version 3 of the {Post Office Protocol}. POP3 is defined in{RFC 1081}, written in November 1988 by Marshall Rose, which is based onRFC 918 (since revised as RFC 937). POP3 allows a {client} computer toretrieve {electronic mail} from a POP3 {server} via a (temporary) {TCP/IP} orother[?] connection. It does not provide for sending mail, which is assumedto be done via {SMTP} or some other method. POP is useful for computers,e.g. mobile or home computers, without a permanent network connectionwhich therefore require a "post office" (the POP server) to hold their mail

until they can retrieve it. Although similar in form to the original POPproposed for the {Internet} community, POP3 is similar in spirit to the ideasinvestigated by the {MZnet} project at the University of California, Irvine, andis incompatible with earlier versions of POP. Substantial work was done onexamining POP in a {PC}-based environment. This work, which resulted inadditional functionality in this protocol, was performed by the {ACIS}Networking Systems Group at {Stanford University}. RFC 1082 (POP3

Extended Service) extends POP3 to deal with accessing mailboxes for{mailing lists}. (1997-01-09)

Definition Provided By Denis Howe


18/57


? IMAP (http://www.definethat.com/define/99.htm)

IMAP Definition

Internet Message Access Protocol. An Internetemail protocol which allows access of your email

from any IMAP compatible browser. Your mailresides on the server level while working withit, versus POP mail which is downloaded intoyour mail program.

Definition Provided By


19/57


? LDAP (http://www.definethat.com) Lightweight Directory Access Protocol Definition

(LDAP) A {protocol} for accessing on-line {directory services}. LDAP wasdefined by the {IETF} in order to encourage adoption of {X.500} directories. The{Directory Access Protocol} (DAP) was seen as too complex for simple {internetclients} to use. LDAP defines a relatively simple protocol for updating and searchingdirectories running over {TCP/IP}. LDAP is gaining support from vendors such as{Netscape}, {Novell}, {Sun}, {HP}, {IBM}/Lotus, {SGI}, {AT&T}, and {Banyan} AnLDAP directory entry is a collection of attributes with a name, called a distinguishedname (DN). The DN refers to the entry unambiguously. Each of the entry's attributes

has a {type} and one or more values. The types are typically mnemonic strings, like"cn" for common name, or "mail" for {e-mail address}. The values depend on thetype. For example, a mail attribute might contain the value"[email protected]". A jpegPhoto attribute would contain a photograph inbinary {JPEG}/{JFIF} format. LDAP directory entries are arranged in a {hierarchical}structure that reflects political, geographic, and/or organisational boundaries. Entriesrepresenting countries appear at the top of the tree. Below them are entriesrepresenting states or national organisations. Below them might be entriesrepresenting people, organisational units, printers, documents, or just about anythingelse. {RFC 1777}, {RFC 1778}, {RFC 1959}, {RFC 1960}, {RFC 1823}. {LDAP v3(http://www.kingsmountain.com/LDAPRoadmap/CurrentState.html)}. [Difference v1,v2, v3?] (2003-09-27)



20/57


? Active Directory (http://www.definethat.com/define/5452.htm)

Active Directory Definition

A {directory service} from {MicrosoftCorporation}, similar in concept to {Novell}

{Netware Directory Services (NDS)}, that alsointegrates with the user organisation's {DNS}structure and is interoperable with{LDAP}. Active Directory is included in{Windows 2000}. (2000-03-28)



21/57


Groupware Servers Newsgroup Server

Newsgroup server provide bulletin-boardlike services


22/57


? RSS (http://www.webopedia.com/TERM/R/RSS.html)

RSS is the acronym used to describe the de facto standard for thesyndicationof Web content. RSS is an XML-based format and while it canbe used in different ways for content distribution, its most widespread usageis in distributing news headlines on the Web. A Web site that wants to allowother sites to publish some of its content creates an RSS document andregisters the document with an RSS publisher. A user that can read RSS-distributed content can use the content on a different site. Syndicated

content can include data such as news feeds, events listings, news stories,headlines, project updates, excerpts from discussion forums or evencorporate information. Because there are different versions of RSS, theterm RSS is most frequently used as a name to mean the syndication ofWeb content, rather than as an acronym for its founding technology. Whenusing the name RSS the speaker may be referring to any of the followingversions of Web content syndication:

RDF Site Summary (RSS 0.9, RSS 1.0) Rich Site Summary (RSS 0.91, RSS 1.0) Really Simple Syndication (RSS 2.0)
http://www.webopedia.com/TERM/R/syndication.htmlhttp://www.webopedia.com/TERM/R/XML.htmlhttp://www.webopedia.com/TERM/R/XML.htmlhttp://www.webopedia.com/TERM/R/syndication.html


23/57


Groupware Servers Calendar Services

Calendar servers provide organization wise scheduling andCalendar services

Calendar servers can be used to setup meetings, reminders andscheduling events

Team members can view others calendar as well

Application can also use Calendar services for automatic schedulingevents

Can be used to even block resources (people, conference, rooms etc)

Calendar Services


24/57


Groupware Servers Workflow services

Workflow: A workflow is a set of interdependent tasks that occur in a

specific sequence. All these tasks together complete a business process

Workflow services are predominantly used in business application Many business transactions require workflow In any application, Workflows can be part manual and part automated

Example: Deposit of a cheque in bank does not end with the deposit After the initial step of deposit, the cheque goes in for clearing from the

issuing bankIf cheque passes, amount is transferred to payees account from the

payers accountTo transfer amount from payers account, there are several steps (Both

physical and electronic) If cheque bounces, then action taken is different. All these tasks put together complete the deposit workflow


25/57


Groupware Service - Workflow

Workflow servers offer workflow services

Can create a workflow which consists of tasks

Can provide decision making points in the

workflow

Programmer can define the workflow paths

Business Applications can use these workflows


26/57


Groupware Servers - Workflow example - Leave System


27/57


Groupware Servers - Workflow example - Leave System


28/57


Database Server With Database servers the client passes SQL requests as

messages to the database servers . The code that processes the SQL request and the data reside on

the same server.

The server uses its own processing power to find the requesteddata. Play an important role in data warehousing.


29/57


Transaction Servers

Client Invokes remote procedures/services that reside on the SQLdatabase engine

TP Monitor (Transaction Processing Monitor) provides TransactionManagement

These remote services execute Group of SQL statements

The Network exchange consists of single request/reply message.

These SQL statements either all succeed or fail which is ensured by

transaction server with TP monitors. Server side business logic typically consists of database

transactions.


30/57


TP Monitors

Routing and Load balancing Same Application can be run on multiple machines for handling load TP monitor is used for load balancing to route a request to least loaded

member of a server machine Run-time platform for distributed application

Types of TP Monitors TP Light (Lite)

An extension to database Example: Sybase Transact SQL, Oracle PL/SQL

TP Heavy Uses database, but outside the database Allows application programmer to write business logic services

Additional Services like scheduling, queuing, buffering etc Security services like Encryption, authentication, and authorization Example: BEA Tuxedo, IBMs CICS


31/57


TP Monitor


32/57


Features of a Client/Server system

Service: There is a relationship between client and server process.

Multi-user support: A single server can entertain requests at a time from many clients

Can share common resources

Transparency of location: (NOS) The environment masks the location of servers from application

Can be accessed from any location

Mix and Match of platforms:

Client and server can be mixed and matched for heterogeneousplatforms

i.e. hardware and operating system can be well intermixed.


33/57


Features of a Client/Server system

Scalability: Scalability of a server or an application is the

ability to provide service without degradation inperformance as load increases

- Client Server applications provide scope forscalability of application


34/57

Network Operating System(NOS)


35/57


Network Operating System (NOS)

Many of the network based services like Fileservices, Mail Services etc. are analogous toservices provided in a system by the OS

A NOS is an extension to OS that providestransparent access to resources on a network. Examples

Novell Netware

UNIX and its variants (HP-UX, Linux) Windows NT, Windows 2000 Adv Server, Windows 2003

Adv Server


36/57


Features of NOS Location transparency: Can access services anywhere

XNet (Extranet) in Infosys can be used to log into Sparsh from anywhere in the

world through a secure network

Logon transparency Same User Id can be used across multiple applications User Authentication done using a common and central system

Examples: Win NT Domain, Kerberos in UNIX world

Replication transparency: Automatic backup and recovery mechanisms One server failure will not result in entire application going down Since difference services are running on different physical servers, failure in one

will not impact on all operations of applications Example: If Mail server goes down, only mail service is affected

Mirror servers are used to avoid failure in critical applications

Resource Sharing: Sharing of resources like files, folders, printers etc

Directory Services: Single point for accessing all the resources in a network Example: Network Neighbourhood, LDAP Protocol used to access directory

services


37/57

Middleware


38/57


Middleware

Middleware is software glue between Client andServer, which helps the communication betweenthe client and the server


39/57


Types of Middleware

Peer to Peer interfaces (P2P) Indicates End to End communication in the same protocol Since the protocol is symmetrical sometimes it is called program to program. In this type of network each workstation has equivalent capabilities andresponsibilities. Example: File sharing systems (Napster etc), Instant Messengers

Remote Procedure Call (RPC) Middleware that allows a computer program running on one host to cause code tobe executed on another host remotely

Programmer doesnt have to explicitly code for achieving this. Middleware provides libraries or functions to achieve this

Message Oriented Middleware (MOM) Uses a queue like structure to pass messages between two hosts Asynchronous connectionless, asynchronous transactional message store-and-forward capability.

Object Oriented Middleware Same as RPC but uses method invocation E.g. ORB (follow CORBA Architecture)


40/57


Remote Procedure Call (RPC)

Client process invokes a remotely locatedprocedure in a server process Server process may or may not reside on the

same physical machine as the client

When a client invokes a remote procedure

The remote procedure executes as if it is a localfunction call

Sends the response back to the client process Involves network communication for data

transfer

RPC uses synchronous communicationbetween client and server Client is blocked until server responds (Client is

typically in a wait state till the responds) Proceeds further only after the server responds.

RPC


41/57


RPC Middleware provides the infrastructure for creating a client-server

application

Translating of clients request into a server side call is handled bymiddleware

Application programmer need not worry about network programming


42/57


RPC - Working of a Simple Server


43/57


Message Oriented Middleware (MOM) A client/server infrastructure that is asynchronous in

nature Client does not wait in a blocked state till the serverresponds

Client can do other tasks while the server processes therequest

Interoperability: Allows the application to bedistributed over multiple heterogeneous platforms.Examples: A mainframe talking to a non-mainframe applications IBM MQ Series is one such Message Oriented

Middleware, JMS in J2EE Applications

Reduces complexity of developing applications that

span multiple operating systems

Masks the application developer from the details ofthe various operating system and network interfaces


44/57


MOM Client initiates communication by putting messages on to the Message

queue

No interaction with server process (de-coupled), thus achievesasynchronous communication Client can continue with other work after putting a message in queue

Message queues also provide temporary storage when the destination program is

busy or not connected

Server uses another queue to send responses back


45/57


Comparing MOM and RPC


46/57



47/57



Splitting an application in a Client/Server Architecture

An application can be split from two perspectives

PERSPECTIVE # 1 : From the perspective of the differentfunctionalities Presentation Logic Business Logic Data Source

PERSPECTIVE # 2 : From the perspective of the concentration of

functionalities Fat Client Fat Server


48/57


PERSPECTIVE # 1 : Application Partitioning - Gartners Group Model


49/57


PERSPECTIVE # 1 : Gartner Group Model

Distributed Presentation Logic: A part of the presentation layer goes to theclient. The other part of presentation layer, business and data managementlayer goes to the server.

Remote Presentation Logic: Only the presentation layer goes to the client.Business and data management layer goes to the server.

Distributed Business Logic: The presentation layer and a part of thebusiness layer goes to the client. The other part of business layer and datamanagement goes to the server.

Remote Data Management: Both the presentation and business layer goesto the client. The data management layer goes to the server.

Distributed Database : Presentation layer, business layer and a part of thedata management layer goes to the client. The other part of the datamanagement goes to the server.


50/57


PERSPECTIVE # 2 : Fat Client and Fat Server

Fat Client: Most of the applications coderesides on client side

Fat Server: Most of the applications coderesides on the server side

What is Thin Client and Thin Server?


51/57


PERSPECTIVE # 2 : FAT Server vs FAT Client


52/57


Client\Server Architecture : 2 Tier

Two-tier applications remain the most common client/serverarchitecture.

The entire application is decomposed into two sets of services.

The client combines UI services + business services and the otherdata services.


53/57


Client\Server Architecture : 3 Tier

It decomposes an application into three sets of services: UI,

business, and data.

Business logic is moved to an application server

Shared data to a database server


54/57


Client\Server Architecture : 2 Tier Vs 3 Tier


55/57


References

1. http://www.lausch.at/gnome/programming

2. docs.sun.com/source/816-5698-10/basics.htm

3. www.ois.com/resources/corb-2.asp


56/57


Summary Standalone (Single User)

Early computing systems, standalone single-user applications

Examples: Calculator, text editor etc

Host Centric (Multi User) Mainframe systems, UNIX systems with terminals Reporting applications, banking etc

Client/Server Client and Servers both have processing capabilities Different types of services provided by servers

Network Operating System

Middleware Peer to Peer RPC MOM



57/57

Thank You!

Documents

BIT3283 (1) INTRO -Client Server Programming 230911_001