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Berkeley Sockets

Berkeley Sockets. The socket primitives for TCP. Some assigned ports. Port. Protocol. Use. 21. FTP. File transfer. 23. Remote login. Telnet. E-mail. 25. SMTP. 69. Trivial File Transfer Protocol. TFTP. Finger. Lookup info about a user. 79. 80. World Wide Web. HTTP. POP-3.

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Berkeley Sockets

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  1. Berkeley Sockets The socket primitives for TCP.

  2. Some assigned ports. Port Protocol Use 21 FTP File transfer 23 Remote login Telnet E-mail 25 SMTP 69 Trivial File Transfer Protocol TFTP Finger Lookup info about a user 79 80 World Wide Web HTTP POP-3 110 Remote e-mail access USENET news 119 NNTP

  3. 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.

  4. Electronic Mail • Architecture and Services • The User Agent • Message Formats • Message Transfer • Final Delivery

  5. Electronic Mail (2) Some smileys. They will not be on the final exam :-).

  6. Architecture and Services Basic functions • Composition • Transfer • Reporting • Displaying • Disposition

  7. The User Agent Envelopes and messages. (a) Paper mail. (b) Electronic mail.

  8. Reading E-mail An example display of the contents of a mailbox.

  9. RFC 822 header fields related to message transport.

  10. Electronic Mail (2) Some smileys. They will not be on the final exam :-).

  11. 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).

  12. MIME (2) RFC 822 headers added by MIME.

  13. MIME types and subtypes (RFC 2045)

  14. A multipart message containing enriched and audio alternatives.

  15. Message Transfer Transferring a message from elinore@abc.com to carolyn@xyz.com.

  16. Message Transfer Transferring a message from elinore@abc.com to carolyn@xyz.com.

  17. Message Transfer Transferring a message from elinore@abc.com to carolyn@xyz.com.

  18. 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.

  19. POP3 Using POP3 to fetch three messages.

  20. IMAP A comparison of POP3 and IMAP.

  21. The World Wide Web • Architectural Overview • Static Web Documents • Dynamic Web Documents • HTTP – The HyperText Transfer Protocol • Performance Ehnancements • The Wireless Web

  22. Architectural Overview (2) The parts of the Web model.

  23. The Client Side (a) A browser plug-in. (b) A helper application.

  24. The Server Side A multithreaded Web server with a front end and processing modules.

  25. The Server Side (2) A server farm.

  26. The Server Side (3) (a) Normal request-reply message sequence. (b) Sequence when TCP handoff is used.

  27. Some common URLs.

  28. Statelessness and Cookies Some examples of cookies.

  29. HTML – HyperText Markup Language (b) (a) The HTML for a sample Web page. (b) The formatted page.

  30. (b)

  31. (b)

  32. XML and XSL A simple Web page in XML.

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