1. © 2010 Computer Science Faculty, Kabul University FTP AND ELECTRONICE MAIL 5 TH LECTURE 4, May, 2010 Baseer Ahmad Baheer

2. © 2010 Computer Science Faculty, Kabul University FTP (File Transfer Protocol) FTP (File Transfer Protocol) is a protocol for transferring a file from one host to another host.

3. © 2010 Computer Science Faculty, Kabul University In order for the user to access the remote account, the user must provide a user identification and a password.

4. © 2010 Computer Science Faculty, Kabul University HTTP and FTP are both file transfer protocols FTP uses two parallel TCP connections to transfer a file, a control connection and a data connection. Server: FileZilla

5. © 2010 Computer Science Faculty, Kabul University

6. FTP Stateful It have to keep track of user state. HTTP Stateless It does not have to keep track of any user state.

7. © 2010 Computer Science Faculty, Kabul University FTP Commands and Replies USER username : Used to send the user identification to server. PASS password : Used to send the user password to the server. LS : Used to ask the server to send back a list of all the files in the current remote directory. GET filename : Used to retrieve (i.e., get) a file from the current directory of the remote host. PUT filename : Used to store (i.e., put) a file into the current directory of the remote host.

8. © 2010 Computer Science Faculty, Kabul University

9. ELECTRONIC MAIL IN THE INTERNET

10. © 2010 Computer Science Faculty, Kabul University Along with the Web, electronic mail is one of the most popular Internet applications. Just like ordinary "snail mail," email is asynchronous -- people send and read messages when it is convenient for them, without having to coordinate with other peoples' schedules.

11. © 2010 Computer Science Faculty, Kabul University Three Components: 1.User Agents/Mail Readers 2.Mail Servers 3.Simple Mail Transfer Protocol Three Components: 1.User Agents/Mail Readers 2.Mail Servers 3.Simple Mail Transfer Protocol

12. © 2010 Computer Science Faculty, Kabul University TCP connection on port 25

13. © 2010 Computer Science Faculty, Kabul University An example transcript between client (C) and server (S), as soon as TCP connection established SMTP uses persistent connections

14. © 2010 Computer Science Faculty, Kabul University SMTP and HTTP both protocols are used to transfer files from one host to another.

15. © 2010 Computer Science Faculty, Kabul University HTTP Is principally a pull protocol HTTP encapsulates each object in its own HTTP response message. SMTP Is primarily a push protocol SMTP requires each message, including the body of each message, to be in seven-bit ASCII format. Internet mail, places all of the message's objects into one message.

16. © 2010 Computer Science Faculty, Kabul University Mail Message Formats Every header must have From: header line and a To: header line A header may include a Subject: header line as well as other optional header lines. A typical message header looks like this:

17. © 2010 Computer Science Faculty, Kabul University The MIME Extension for Non-ASCII Data Multipurpose Internet Mail Extensions (MIME) is an Internet standard that extends the format of e-mail to support: Text in character sets other than ASCII Non-text attachments Message bodies with multiple parts Header information in non-ASCII character sets

18. © 2010 Computer Science Faculty, Kabul University Two key MIME headers for supporting multimedia are the

19. © 2010 Computer Science Faculty, Kabul University

20. Base64

21. © 2010 Computer Science Faculty, Kabul University text/plain, text/html image/jpeg, image/gif application/msword multipart/mixed Video/format Audio/format

22. © 2010 Computer Science Faculty, Kabul University

23. References MIME, http://www.faqs.org/rfcs/rfc1521.htmlhttp://www.faqs.org/rfcs/rfc1521.html MIME Types By Content Type, http://www.w3schools.com/media/media_mimeref.asp http://www.w3schools.com/media/media_mimeref.asp