1. HTTP By: Becky Fultz, Joe Flager, Katie Huston, Tom Packard, Allison Wilsey

2. What is HTTP? HyperText Transfer Protocol Invented by Tim Berners-Lee in 1989 Defines how messages are formatted and transmitted Also, what actions web servers and browsers should take in response to different commands

3. History of HTTP Tim Berners-Lee created the first server and hypertext browser/editor know as the “World Wide Web” in 1990 In 1991 the “web” was made available on the internet by providing his previous creations of HTML, HTTP, and UDI (URL) This uniform code made it easy for everyone to be connected and “speaking” the same language

4. World Wide Web Consortium (W3C) International Consortium created in 1994 by a group of individuals among whom included Tim Berners-Lee Mission Statement: “To lead the World Wide Web to its potential by developing protocols and guidelines that ensure long-term growth for the web” Purpose is to create web standards and guidelines called the W3C recommendations Since 1994 they have published more than 90 recommendations90 recommendations

5. W3C Goals 1. Web for Everyone 2. Web on Everything 3. Knowledge Base 4. Trust and Confidence

6. How HTTP Works HTTP client sends a request using a transmission control protocol (TCP) connection to a port on a remote host An HTTP server connected to that port waits to receive the client’s message before it acts The server sends back a status line The status line could be the requested file, an error message, or some other info –An example is HTTP/1.0 404 Not FoundAn example is HTTP/1.0 404 Not Found –Other users will see this errorOther users will see this error The HTTP server then closes the connection, known as Stateless Protocol

7. Request Message The request message is sent from the client to the server The format for this message is as follows: –Request Line –Header –Empty Line –Optional Message Body The request line and headers must all end with CRLF (which stands for Carriage Return and Line Feed)

8. Request Line The request line has 3 parts: –Method –Local path of the resource –HTTP Version

9. Request Methods There are 8 methods that indicate how the task is to be carried out GET: Request a representation of the specified resource HEAD: Asks for the response identical to the one that would correspond to a GET request, but without the response body.

10. Request Methods POST: Submits user data to the identified resource PUT: Uploads a representation of the specified resource DELETE: Deletes the specified resource OPTIONS: Returns the HTTP methods that the server supports.

11. Request Methods CONNECT: For use with a proxy that can change to being an SSL tunnel TRACE: Echoes back the received request, so that a client can see what intermediate servers are adding or changing in the request Safe methods are designed only for information retrieval. The methods are GET and HEAD Unsafe methods are designed to make a user aware of possible side effects of their actions. These methods should be displayed in a special way such as a button.

12. Status Codes Status codes are informational groupings that are given by the server to the client as a status report Status codes are always three digits, and the first digits indicates what happened: 1xx – informational message only 2xx – indicated a success 3xx – redirects the client to another URL 4xx – indicates an error on the client’s part 5xx – indicates an error on the server’s part Some common status codes are:  202 means that everything went ok and the file is in the message body  301 means that the file has been moved permanently  302 means that the file has been moved temporarily  404 means that the file does not exist  505 means an unexpected server error

13. Break Down a URL URL - Uniform Resource Locator (This is a subset of URI, which is a uniform resource identifier) Unique address –File –ImageImage –Website Contains: –Program used to access the resource –Specific computer that the file is stored in –File name of the resource including the path of how to get to it

14. URL Example http://en.wikipedia.org:80/wi ki/Special:search?search=trai n&go=Go

15. Wrap-Up Invented in 1989 by Tim Berners-Lee Helped connect everyone by using the same language Very complex and rigid format

16. QUESTIONS????