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1、CHAPTER 2 The Internet and World Wide WebOther Internet ServicesE-Mail-Electronic MailSend mail electronically via the InternetSend mail electronically via the InternetRequires an account on a mail server and supporting software on your PCRequires an account on a mail server and supporting software
2、on your PCThe username and password will allow you to access your accountThe username and password will allow you to access your accountAll e-mail programs allow you to Send,Compose,Reply,and Forward mailAll e-mail programs allow you to Send,Compose,Reply,and Forward mailObtaining an E-mail AccountY
3、ou will need an e-mail server(post office)in order to send and You will need an e-mail server(post office)in order to send and receive e-mail.receive e-mail.You can obtain an account in schoolYou can obtain an account in schoolYou can pay for an account through an ISP such as AOLYou can pay for an a
4、ccount through an ISP such as AOLYou can get free accounts:You can get free accounts: Privacy and Terms of AgreementE-mail is less private than US mailE-mail is less private than US mail If you need privacy,send a letterIf you need privacy,send a letterEvery mail server has terms that you must agree
5、 to Every mail server has terms that you must agree to No copyright infringementsNo copyright infringements No harassing or stalkingNo harassing or stalking No junk mail or spammingNo junk mail or spamming No intentional sending of virusesNo intentional sending of virusesThe Mail FoldersInboxInbox n
6、ew messages as well as messages that have been read new messages as well as messages that have been readOutboxOutbox messages not yet sent messages not yet sentSent itemsSent items messages that have been sent(moved here from outbox)messages that have been sent(moved here from outbox)Deleted itemsDe
7、leted items messages deleted from any folder messages deleted from any folderCustom foldersCustom folders additional folders created by the user additional folders created by the userAn E-mail AddressEvery e-mail address is unique and consists of two parts,a user name and a Every e-mail address is u
8、nique and consists of two parts,a user name and a host computerhost computerThe sign is requiredThe sign is requiredThe host computer can be omitted if you are logged onto the same network or The host computer can be omitted if you are logged onto the same network or host computer host computer Inte
9、rnet Messaging EmailEmail Asynchronous communication:user does not have to be online for message to be delivered Asynchronous communication:user does not have to be online for message to be delivered(not(not instantinstant messaging)messaging)NewsgroupsNewsgroups Instant Messaging and PresenceInstan
10、t Messaging and Presence UNIX included finger and talkUNIX included finger and talk Finger:determine the presence(or status)of other usersFinger:determine the presence(or status)of other users Talk:text based instant chatting applicationTalk:text based instant chatting application Internet Relay Cha
11、t(IRC)Internet Relay Chat(IRC)Introduced in 1988 as group based,instant chatting serviceIntroduced in 1988 as group based,instant chatting service Users join a chat roomUsers join a chat room Networks consist of servers connected together,and clients connect via a single serverNetworks consist of se
12、rvers connected together,and clients connect via a single server ICQ(“I Seek You”)ICQ(“I Seek You”)Introduced in 1996,allowing chatting between users without joining chat roomIntroduced in 1996,allowing chatting between users without joining chat room In 1998 America Online(AOL)acquired ICQ and beca
13、me most popular instant messaging In 1998 America Online(AOL)acquired ICQ and became most popular instant messaging application/networkapplication/network AIM,Microsoft MSN,Yahoo!Messenger,Jabber,AIM,Microsoft MSN,Yahoo!Messenger,Jabber,Initially,Microsoft and Yahoo!Created clients to connect with A
14、IM serversInitially,Microsoft and Yahoo!Created clients to connect with AIM servers But restricted by AOL,and most IM networks were limited to specific clientsBut restricted by AOL,and most IM networks were limited to specific clients Only recently(1-2 years)have some IM networks opened to different
15、 clients Only recently(1-2 years)have some IM networks opened to different clients Instant Messaging and PresenceInstant MessagingInstant Messaging Synchronous communications:message is only sent to destination if recipient is willing to Synchronous communications:message is only sent to destination
16、 if recipient is willing to receive it at time it is sentreceive it at time it is sentPresencePresence Provides information about the current status/presence of a user to other usersProvides information about the current status/presence of a user to other users Other users can subscribe to the prese
17、nce information of a particular userOther users can subscribe to the presence information of a particular user E.g.:Online,Busy,Away,OfflineE.g.:Online,Busy,Away,Offline Controls what messaging options are available(cannot send message when someone is Controls what messaging options are available(ca
18、nnot send message when someone is offline)offline)NamingNaming Most systems use email address format for namingMost systems use email address format for namingPopular IM Applications/NetworksClosed use proprietary protocols,normally limiting only their own clients to Closed use proprietary protocols
19、,normally limiting only their own clients to access networkaccess network AOL Instant Messaging(AIM)AOL Instant Messaging(AIM)Microsoft Messenger(MSN)Microsoft Messenger(MSN)Also known as Windows Messenger,Live MessengerAlso known as Windows Messenger,Live Messenger Yahoo!Messenger(YMSG)Yahoo!Messen
20、ger(YMSG)Open use open(published)protocols,normally allowing any client to access Open use open(published)protocols,normally allowing any client to access networknetwork Jabber and XMPPJabber and XMPPComparing AIM,MSN and YMSGFeatures and FunctionsMaintaining lists of friends(and enemies)Maintaining
21、 lists of friends(and enemies)Buddy list:users who are considered friends;notified of presence of these usersBuddy list:users who are considered friends;notified of presence of these users Block list:users who cannot contact youBlock list:users who cannot contact you Allow list:users that can contac
22、t youAllow list:users that can contact you Reverse forward lists:users that have you on their allow listReverse forward lists:users that have you on their allow list All lists are maintained on provider servers;synchronised when a user logs inAll lists are maintained on provider servers;synchronised
23、 when a user logs inMessages to describe users current typing activity:Messages to describe users current typing activity:E.g.typing,not typing,typed but erasedE.g.typing,not typing,typed but erasedDeliver messages to users that are not online(similar approach to how email Deliver messages to users
24、that are not online(similar approach to how email works)works)Secure communications(at least offered by AIM)Secure communications(at least offered by AIM)SSL used to secure messages and chat roomsSSL used to secure messages and chat roomsWhy do we need a FTP Service?Purpose:To Transfer files between
25、 two computersGoals of FTP Service Promote sharing of files(programs and/or data)Encourage indirect/implicit use of remote computers Shield users from variations in file storage among hosts Transfer data reliably and efficientlyProblems of File TransferAt first,file transfer may seem simpleAt first,
26、file transfer may seem simpleHeterogeneous systems use different:Heterogeneous systems use different:Operating SystemsOperating SystemsCharacter SetsCharacter SetsNaming ConventionsNaming ConventionsDirectory StructuresDirectory StructuresFile Structures and FormatsFile Structures and FormatsFTP need to address and resolve these problemsFTP need to address and resolve these problemsFTP Connections FTP Connectionftp open serverSYNSYN|ACKACK220 Service Readyftp USER haggertyACKACK331 User OK,password?ACKftp PASS mypassACK230 User login OKACKClientServer