1. Skills: none Concepts: protocol, hypertext transfer protocol, standard This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License. HTTP, the hypertext transfer protocol

2. Where does this topic fit? Internet concepts – Applications – Technology – Implications Internet skills – Application development – Content creation – User skills

3. 1. Establish a temporary connection between the client and server 2. Client sends the request to the server 3. Server returns the requested page or an error message 4. Client displays whatever the server returns 5. Disconnect – drop the connection Client Server request page Summary: retrieving a Web page

4. The client-server conversation I would like to open a connection GET Display response Close connection OK Send page or error message OK ClientServer

5. The HTTP GET command GET /fac/lpress/shortbio.htm HTTP/1.0

6. Who invented HTTP? Do you know his name?

7. Formal conversation protocols Describe the protocol governing a conversation with Queen Elizabeth.

8. Protocols establish standards, facilitating competition Opera Chrome Safari Firefox Internet Explorer What are some other standards that facilitate competition?

9. Standards yield competition

10. Some other application protocols ProtocolApplication HTTP: Hypertext TransferRetrieve and view Web pages FTP: File Transfer Copy files from client to server or from server to client SMTP: Simple Mail TransportSend email POP: Post OfficeRead email

11. A complete page request GET /fac/lpress/shortbio.htm HTTP/1.0 Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/vnd.ms-powerpoint, application/vnd.ms-excel, application/msword, Accept-Language: ko,en-us;q=0.5 User-Agent: Mozilla/4.0 (compatible; MSIE 5.5; Windows NT 5.0) Host: som.csudh.edu Proxy-Connection: Keep-Alive

12. Summary

13. Self-study questions 1.What would happen if the client program had a bug and sent a request with the command name spelled GETX instead of GET? 2.As a Web user, do you have to be concerned with the details of HTTP? 3.As a programmer writing a Web client, do you have to be concerned with the details of HTTP? 4.As a programmer writing a Web server, do you have to be concerned with the details of HTTP? 5.As a user of a Web service, do you have to be concerned with the details of HTTP?

14. Resources Definition of the HTTP standard: http://www.w3.org/Protocols/