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Understanding Berkeley Sockets and Electronic Mail Protocols

Explore the fundamentals of Berkeley Sockets for TCP connections and delve into electronic mail protocols, MIME, message transfer, POP3, IMAP, and the World Wide Web architecture. Learn about ports, protocols, message formats, and more in this comprehensive guide.

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Understanding Berkeley Sockets and Electronic Mail Protocols

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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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