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Learn the basics of web application development, including networks, client-server models, databases, transmission protocols, IP addresses, ports, DNS, and more.
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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
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
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
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
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 8th power = 256) • USUALLY each computer will be assigned to one unique IP address
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
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
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
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
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)
Chapter 1 . Overview • Tools for checking the connectivity • For TCP/IP or UDP(user datagram)/IP • Ping: ICMP packet (ping of death) • tracert • nslookup