Post on 31-Dec-2015
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File Transfer Protocol (FTP)
FTP host stores files Client logs into host Client program sends command to get a file FTP host downloads the file with error correction
FTP Host
2. FTP Get Command
3. Download
1. Login
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File Transfer Protocol (FTP)
User can also upload a file to the FTP Server
– WWW cannot do this
FTP Host
2. FTP Upload
1. Login
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File Transfer Protocol (FTP)
Must Log into FTP Host Before Transfers
Traditional FTP– You log into a specific account with a password– You can transfer to and from directories accessible to that
account
Anonymous FTP– You log in as “anonymous”– Give your e-mail address as password (usually optional)– Host gives you access to public directories– Usually for downloading only– Not truly anonymous: your internet address is known
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FTP File Format Standards
There are no standards for FTP file formats
– Nothing like HTML
– No limit on generality
– No help in handling after downloads
– You must know the file structure of the file you download
– You must have an application program that can read that file format
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FTP Archiving
Many FTP files are archived
– Two-step process
– First, several files are combined into one archive to avoid having to make multiple downloads
– Second, the combined files are compressed to reduce download times
1.Combine
2.Compress
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FTP Archiving
Receiver must dearchive the files to read them
Unfortunately, many archiving standards– Zip is the most common
– UNIX users tend to use others
– Some dearchiving programs handle only one archiving standards, others several
Dearchive
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FTP Archiving
Receiver must dearchive the files to read them
Self-Dearchiving Files– Usually, you need a dearchiving program to dearchive
– However, some archives have the extension .exe
– Really programs; Dearchive themselves
– Executing the archive file dearchives its files
– These are programs, so be wary of viruses!
Dearchive
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LISTSERV
LISTSERV Host Maintains Lists of E-Mail Addresses
– You subscribe to a specific list
– Messages posted to the list are mailed to you
– You receive them in your ordinary e-mail system
Postingvia E-Mail
Deliveryvia E-mail
LISTSERV host
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There is a LISTSERV host computer with a hostname (puka.org in this example)
A LISTSERV program manages conferences on the host (in this case, the program is named LISTSERV)
The program manages multiple conferences (GLOBAL-L and CRIME-L in this example)
A LISTSERV Conference
LISTSERV Hostpuka.org
LISTSERV Program GLOBAL-L Conference CRIME-L Conference
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Subscribing to a LISTSERV Conference
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
1.
Subscription message is sent to the list management program, LISTSERV, not to a specific conference
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Subscribing to a LISTSERV Conference
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
2.
Subject field can be left blank; You can have a subject if you like, but it will be ignored
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Subscribing to a LISTSERV Conference
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
3.
Body must read as follows:
subscribe conferencename yourname
Not “subscribe to”No period at end
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Subscribing to a LISTSERV Conference
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
To: LISTSERV@puka.orgSubject:----------------------------------subscribe GLOBAL-L Ray Panko
Nothing else may be in the body
In particular, you must NOT have a signature
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Common Errors
Sending the subscription message to a conference name, not to the LISTSERV manager program– It doesn’t work– It goes to everyone in the conference, annoying them
Not typing “subscribe conferencename yourname” (without the quotes) exactly
Adding a signature or any additional text in the body
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Posting a LISTSERV Message
To: GLOBAL-L@puka.orgSubject: Gigaplexe?-------------------Is anyone using one of the newGigaplexe LANs in Europe?
To: GLOBAL-L@puka.orgSubject: Gigaplexe?-------------------Is anyone using one of the newGigaplexe LANs in Europe?
1.
Post the message to the conferencename at the host, not to the LISTSERV manager program, LISTSERV
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Posting a Content Message to a Group
To: GLOBAL-L@puka.orgSubject: Gigaplexe?-------------------Is anyone using one of the newGigaplexe LANs in Europe?
To: GLOBAL-L@puka.orgSubject: Gigaplexe?-------------------Is anyone using one of the newGigaplexe LANs in Europe?
2.
Always add a descriptive Subject field
3.
Put whatever you like in the Body
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Unsubscribing from a LISTSERV Conference
Send an unsubscribe message to the LISTSERV management program– In this case, LISTSERV– NOT to the conference!!!!!!!!!– Be sure to record the name of the management program
when you subscribe so you can unsubscribe later
Body must read (exactly)– unsubscribe conferencename
Nothing else must be in the body– In particular, the message may not have a signature
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Recap Subscribing (Supervisory Message)
– Send message to LISTSERV manager– Not to the conference name!– Body: “subscribe conferencename yourname”– No signature or anything else
Posting (Content Message)– Send postings to conferencename
Unsubscribing (Supervisory Message)– Must unsubscribe to stop getting mail– Send message to LISTSERV manager– Nothing in body except “unsubscribe conferencename”
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USENET
Conceptually like reading magazines
USENET hosts
– Like bookstores
Each host has many Newsgroups on specific topics
You can read postings to these Newsgroups
Anyone can post new messages to these Newsgroups
Usenet Hostwith Multiple Newsgroups
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USENET Browsing Newsgroups
– Host maintains many conferences (Newsgroups)– Connect to any USENET host (there are thousands)– Subscribe to Newsgroups (there are thousands)– Read postings to subscribed newsgroups
Usenet Hostwith Multiple Newsgroups
ClientHost Connect, choose Newsgroup
Read Postings
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USENET
There are many USENET hosts– Postings to one are replicated (copied) to all others– May take time– Not all USENET hosts support all Newsgroups
Posting
Copy
Copy
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USENET Newgroups
Organized Hierarchically to help users find relevant newsgroups
Root (all groups)
Comp Alt
Comp.risks Comp.dcom
Comp.dcom.cabling Comp.dcom.servers
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Reading Newsgroups
Menu Bar
Subscribed NewsgroupsComp.dcom.cabling...
Comp.dcom.CablingQuestion on cabling Re: Question on ...
Subject: Re: Question on cablingFrom: Pat Lee <Pat.Lee@Busad.Waikiki.edu-----------Bill, we ran into the same problem. Use duct tape.
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Threads
Replies are grouped under original messages
– Original message plus replies is called a thread
– Easy to follow content
RJ-45 problem
Question Regarding Cabling
Re: Question Regarding Cabling
Re: Question Regarding Cabling
Re: Re: Question Regarding Cabling
Enhanced Category 5?
Thread
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LISTSERVs vs. USENET
LISTSERVs
– No need to check for new postings: delivered via e-mail
– Must remember how to unsubscribe
– Must find the LISTSERV host holding the conference
USENET
– Will not clog your mailbox with “junk mail”
– Log into almost any USENET host to find a particular Newsgroup
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Moderated Conferences
Moderated Conference
– Moderator reads postings that arrive
– Posts to conference only if relevant, polite
Unmoderated Conferences
– No moderator
– All postings are made available as soon as they arrive
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Telnet
Traditional Terminal-Host Communication– Log into host computer– You can run programs there, such as E-mail– Processing is done on the host– Expensive if long-distance connection
HostTerminal orPC Emulatinga Terminal
Phone Line
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Telnet
Uses Internet to Connect to Host
– Can access host from anywhere on the Internet
Telnet Software on Client Host– Manages login, use, and disconnections
Telnet Telnet
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Telnet
Poor User Interface
– Based on dumb VT100 terminal (Module H)
– Text-only display
– Monochrome (One color for text, one for background)
– Have to type command-line commands Often have complex syntax