84network - Lecture Outline 8 Networking Networking...

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Introduction to Computer Science • Robert Sedgewick and Kevin Wayne • 8 Networking If you have a wireless laptop, download the following programs: 2 Lecture Outline Networking. ! Communicate between different devices. ! Client-server. ! Peer-to-peer. Networking in Java. ! Mail spoofing. ! Echo. ! Remote control. ! Chatroom. Detours. ! Graphical user interface. ! Threads. 3 The Telephone Network Telephone network. ! Circuit switching: single physical path between sender and receiver is dedicated for duration of communication. ! Has worked for 100 years. ! Advantage: real-time communication. 4 Internet Internet. ! Global communication network containing million of computers. ! Computer networks communicate using TCP/IP protocol. ! Provides access to services: email, chat, world wide web, KaZaa. ! Started by military around 1969 as ARPANET: survivability, robustness, efficiency. ! Operating system and hardware independent. Everybody but you grew up without it!
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5 TCP/IP Internet protocol. (IP) ! Rules for moving bits from A to B. ! Divide data into packets (header bits to say where to go, data bits) and transmit each individually, possibly along different paths. ! No guarantee packets arrive in order, or even arrive. Transmission control protocol. (TCP) ! Rules to provide reliable communication between two computers. ! Packets arrive, and they arrive in order. resend over IP until recipient acknowledges Reference: COS 111 lecture notes. 6 Protocols Many higher layer application protocols use TCP/IP. ! Used by http, smtp, telnet, ftp. Ex 1: HyperText Transfer Protocol (HTTP). ! Set of rules for transferring files (text, graphics, video). ! Server java.sun.com waits for connection requests. ! Browser establishes connection with server at . ! Browser issues GET and POST commands. ! Server responds with header and body. tells system to use http protocol to get the specified resource ISO 7-layer model 7 SMTP Ex 2: Simple Mail Transfer Protocol (SMTP). ! Set of rules for sending email. ! Server smtp.princeton.edu waits for connection requests on port 25 . ! User specifies sender, recipient, subject, message body, etc. Open relay. smtp server accessible from anywhere. phoenix.Princeton.EDU% telnet smtp.princeton.edu 25 220 smtpserver1.Princeton.EDU ESMTP Sendmail 8.12.9/8.12.9; Sun, 7 Dec 2003 09:18:47 -0500 (EST) HELO localhost 250 smtpserver1.Princeton.EDU Hello phoenix.Princeton.EDU [128.112.128.42], pleased to meet you MAIL From: AlanTu[email protected] 250 2.1.0 [email protected] Sender ok RCPT TO: [email protected] 250 2.1.5 [email protected] Recipient ok DATA 354 Enter mail, end with "." on a line by itself Subject: Just wanted to say hi Hope you're enjoying COS 126.
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  • Spring '16
  • dncj ncnd
  • Networking, E-mail, Simple Mail Transfer Protocol, Socket socket

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