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

© 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.

© 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.

© 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

© 2010 Computer Science Faculty, Kabul University

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

© 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.

© 2010 Computer Science Faculty, Kabul University

ELECTRONIC MAIL IN THE INTERNET

© 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," is asynchronous -- people send and read messages when it is convenient for them, without having to coordinate with other peoples' schedules.

© 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

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

© 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

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

© 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.

© 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:

© 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 to support: Text in character sets other than ASCII Non-text attachments Message bodies with multiple parts Header information in non-ASCII character sets

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

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Base64

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

© 2010 Computer Science Faculty, Kabul University

References MIME, MIME Types By Content Type,