1. IS 247 Introduction to Web Application Development Tim Wu

2. Chapter 1. Overview What is a Network? –Devices (computers and printers) connected by wires (copper, fiber-optic), or wireless (radio waves) –Local Area Network (LAN) / Wide Area Network (WAN) –Internet: Network of Networks World Wide Web (www, w3, web) –Part of the network services –First online graphical system –Web page: display text, images, audio, video

3. Chapter 1. Overview Client Server Model –Talking about the “Function” of a computer/computers –Client Computer: using client program to send request to server computer and receive answer from server computer –Server Computer: using server program to receive/process client computer and return result to server computer daemon / service: a process that listens to client request

4. Chapter 1. Overview Client Server Model –Database: A set of data that is organized and store in file (s) –Two-tier model [ Client ] [Web Server] + [Database Server] –Three-Tier model [ Client ] [Web Server] [Database Server] –Application Server/Services Provider (ASP) A out-sourcing solution

5. Chapter 1. Overview Transmission across the Internet –Transmission protocol Transmission Control Protocol / Internet Protocol (TCP/IP) –TCP form data into Packets / IP sent Packets to destination –Transmission devices PC with Network Interface Card (NIC) Hub / Switch Router Modem

6. Chapter 1. Overview IP Address –32 bits dotted decimal notation address and contains four fields which are decimal values representing 8 bits binary octets. –An binary IP address 10000001.00000101.0000101.01100100 coverts to decimal format is 129.5.10.100 –Each of four numbers of an IP address is a value between 0~255 ( 2 to 8 th power = 256) –USUALLY each computer will be assigned to one unique IP address

7. Chapter 1. Overview TCP Port –Enables communication between individual process at two communicating device (Computers, Printers..) –Each communicating process has its own assigned port or ports –HTTP port 80 - HTTPS port 443 –FTP port 21 - SSH port 22 –DNS 42- SMTP port 25

8. Chapter 1. Overview Domain Name System - DNS –Assign name to IP address (Server) –www.emich.edu, ftp.microsoft.com –Rule: Host name + domain name (sub-domain name) Uniform Resource Locator – URL –Protocol Name + Server Name + port number (optional) –http://people.emich.edu:80 –Default web page name: index.html, index.htm, default.htm

9. Chapter 1. Overview Internet, Intranet and Extranet –Firewall: Could be server or appliance filtering network traffic by intercepting every incoming & outgoing packets creating secure channel between computers or networks by encrypting all the data

10. Chapter 1. Overview Connecting to Internet –Internet Service Provider – ISP –Different kind of connections: Dial-Up modem ~ 56 kb/sec download Digital Subscriber Line ~ 256 kb/sec download Cable modem ~ 6 mb/sec download T-carrier system –T1 ~ 1.5 mb/sec –T3 ~ 45 mb/sec

11. Chapter 1. Overview Windows ICP/IP Socket - winsock –A virtual link between client and server computer –Operating System usually provide the function (library) for programming language to use (call) it –In Windows system the library is called Dynamic Link Library (DLL)

12. Chapter 1. Overview Tools for checking the connectivity –For TCP/IP or UDP(user datagram)/IP –Ping: ICMP packet (ping of death) –tracert –nslookup