Internet Basics

1. Internet Basics What is a web page? A browser is a specialized piece of software designed to decode XHTML code.

2. Internet Basics What is a web page? A web page is an XHTML file sitting on a computer somewhere. index.html Example XHTML code

3. Internet Basics What is a web page? The internet allows us to transfer HTML files from one computer to another.

4. Internet Basics What is the internet? The internet is a worldwide network of computers connected together. Some of these computers are clients Others computers are servers

5. Internet Basics Clients and Servers Clients and servers are connected together through the internet. The computer which stores the web page is called the server because it is giving, or serving, the web page to your computer. When you use the World Wide Web, your computer is a client because it is requesting a web page. Key Point: Clients get web pages from servers. Servers give web pages to clients.

6. Internet Basics Transferring HTML files from servers to clients Step 1: Client requests an HTML file from Server “I’d like homepage.html” Step 2: Server sends the HTML file to the Client

7. Internet Basics How do clients and servers find each other? Are you my mother?

8. Internet Basics How do clients and servers find each other? IP Address 134.84.119.107 121.77.148.15

9. Internet Basics How do clients and servers find each other? 218-879-3393 Ring! Ring! Ring!

10. Internet Basics Transferring HTML files from servers to clients Step 1: Client requests an HTML file from Server “134.84.119.107:I’d like homepage.html. Send it to 121.77.148.15” Step 2: Server sends the HTML file to the Client

11. Internet Basics Transferring HTML files from servers to clients

12. Internet Basics Domain Name Service Some computers connected to the internet are called DNS Servers.

13. Internet Basics Domain Name Service What’s the IP address for umn.edu? Step 1: Client requests an HTML file from Server “134.84.119.107:I’d like homepage.html. Send it to 121.77.148.15” Step 2: Server sends the HTML file to the Client

14. Internet Basics Uniform Resource Locators http://www.stcloudstate.edu

15. Internet Basics Uniform Resource Locators http://www.stcloudstate.edu • Domain Name • This tells you which computer the HTML file is on • This gets resolved into an IP address by a DNS server • Each domain name has its own unique IP address

16. Internet Basics But Where? http://www.stcloudstate.edu/

17. Internet Basics But Where? http://www.stcloudstate.edu/project1.html

18. Internet Basics But Where? http://www.stcloudstate.edu/project1.html Client: What’s the IP address for stcloudstate.edu? DNS Server: stcloudstate.edu = 134.80.77.19 Client: I’m calling 134.80.77.19 and am requesting the file, project1.html St. Cloud State Server: Here’s project1.html Client: Receives project1.html and opens it with Internet Explorer. Internet Explorer is software which reads the XHTML instructions and displays the web page.

19. Internet Basics But Where? http://www.yahoo.com • Now What? • This URL does not include a filename. • In this case, the server will always transmit… index.html

20. Internet Basics But Where? index.html • One of your pages should always be called index.html • index.html is the first page the server will give whenever a client requests a website • index.html should always be your HOME PAGE

21. Internet Basics Which HTML file? What’s the IP address for umn.edu? DNS Server St. Cloud State Server Step 1: Client requests an HTML file from Server “134.84.119.107:I’d like your home page. Send it to 121.77.148.15” Step 2: Server sends the HTML file to the Client If the client asked for a specific file, send that file. Otherwise, automatically send index.html