Lecture 0 - Part1 "HTTP" - Building Dynamic Websites HarvardOpencourseWare. CS75

Harvard OpenCourseWare. (Summer 2012)

Lecture 0 "HTTP" - Building Dynamic Websites

Summary: This is the first lecture of the series. Building Dynamic Websites by Harvard OpenCourseWare with Great Instructor David J. Malan

Video Run Time:　 1:46:19

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Lecture 0: HTTP

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Lecture #0 Summary

Part-1

1. http protocol
2. Look at the http header
3. How "internet" find the host, e.g. google.com, specified in a URL
4. How query parameter in a URL is passed
5. DHCP
6. Connecting to a remote host via telnet with IP address

Part-2

1. GET / HTTP/1.1 command in telnet
2. HTTP/1.1 400 bad request
3. HTTP/1.1 Error 301 - Moved permanently
4. dhcp commad
5. dhcp nslookup cnn.com and check the IP address
6. /private/etc/hosts file for host database that lists 127.0.0.1 for localhost
7. Use Chrome advanced feature for a developer to inspect the HTML element for style (button length)

0.1  http protocol

0.1.1 IP Address, DNS

When you type a search key word in www.google.com, what happens?

Explain what actually happens behind the scene.

1. Hit enter in the google search field.

2. Translate the URL (www.google.com) to IP address.

3. IP address: w.X.Y.Z 0 to 255  2EXP(32), 32 bits about 4 billion IP addresses.

4.That's version 4 IP address

5. Domain name lookup by DNS server that converts URL to the corresponding IP address.

6. Hieralchy of DNS system to find a known URL.

7. A root server knows who knows the URL in .com or .net, etc.

8. HTTP / GET / 1.0 (a header in a virtual envelope)

9. Default gate way (Router) routes a virtual envelope

10. Once a destination server receives the envelope, performs a service,

11. Repackage a virtual envelope and send it to the "from address".

0.1.2 Private IP Addresses

At home, we have private IP addresses. For example,

  192.168.x.x

  172.16.y.y

   10.z.z.z (Class A IP address)

Port forwarding

TCP/IP Stack

Port Number, 

Listening on port Number 80 (common)

port #25 (mail)

All traffic comes to a specific port

HTTP #443