Berkeley Sockets
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Transcript of Berkeley Sockets
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Berkeley Sockets
The socket primitives for TCP.
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Port Protocol Use21 FTP File transfer23 Telnet Remote login25 SMTP E-mail69 TFTP Trivial File Transfer Protocol79 Finger Lookup info about a user80 HTTP World Wide Web
110 POP-3 Remote e-mail access119 NNTP USENET news
Some assigned ports.
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Headers
(a) Four 512-byte segments sent as separate IP datagrams.(b) The 2048 bytes of data delivered to the application in a single
READ CALL.
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Electronic Mail• Architecture and Services• The User Agent• Message Formats• Message Transfer• Final Delivery
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Electronic Mail (2)
Some smileys. They will not be on the final exam :-).
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Architecture and ServicesBasic functions• Composition• Transfer• Reporting• Displaying• Disposition
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The User Agent
Envelopes and messages. (a) Paper mail. (b) Electronic mail.
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Reading E-mail
An example display of the contents of a mailbox.
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RFC 822 header fields related to message transport.
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Electronic Mail (2)
Some smileys. They will not be on the final exam :-).
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MIME – Multipurpose Internet Mail Extensions
Problems with international languages:• Languages with accents
(French, German).• Languages in non-Latin alphabets
(Hebrew, Russian).• Languages without alphabets
(Chinese, Japanese).• Messages not containing text at all
(audio or images).
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MIME (2)RFC 822 headers added by MIME.
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MIME types and subtypes (RFC 2045)
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A multipart message containing enriched and audio alternatives.
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Final Delivery
(a) Sending and reading mail when the receiver has a permanent Internet connection and the user agent runs on the same machine as the message transfer agent. (b) Reading e-mail when the receiver has a dial-up connection to an ISP.
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POP3
Using POP3 to fetch three messages.
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IMAPA comparison of POP3 and IMAP.
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The World Wide Web• Architectural Overview• Static Web Documents• Dynamic Web Documents• HTTP – The HyperText Transfer
Protocol• Performance Ehnancements• The Wireless Web
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Architectural Overview (2)
The parts of the Web model.
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The Client Side
(a) A browser plug-in. (b) A helper application.
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The Server Side
A multithreaded Web server with a front end and processing modules.
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The Server Side (2)
A server farm.
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The Server Side (3)
(a) Normal request-reply message sequence.(b) Sequence when TCP handoff is used.
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Some common URLs.
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Statelessness and Cookies
Some examples of cookies.
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HTML – HyperText Markup Language
(a) The HTML for a sample Web page. (b) The formatted page.
(b)
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(b)
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(b)
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XML and XSL
A simple Web page in XML.
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