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TCP/IP Servers • • • • • • LPD (Printing) SMTP (Mail) FTP (File Transfer) NTP (Network Time) NNTP (News) WEB Network Printing • Configure the printer hardware on the host system by using either the parallel or usb interfaces. • Add the Windows component “Other Network File and Printing Services” – uses port 515 (LPD) for BSD Unix printing • Or get HP JetAdmin software for the system – uses port 9100 (Jet Direct) • Or get a network ready printer Printing cont. • Printer protocols: – Postscript (Adobe) • is a language executed by the printer • is very configurable – PCL (Hewlett Packard) • is a bit mapped graphics mode • is faster than postscript – ASCII (text) • Plain old printable characters Printer Setup (Network Ready) • Plug it in to the wall outlet (power) • Plug in the network cable • Power up the printer • Print the configuration sheet • Register the printer address (preferably non-routable) Printing • PDL (Print Description Languages), basically printer drivers. • Provide a standard interface from the application to the printer. Printer maintenance • Expendable supplies (paper and toner) • How to fix a paper jam • Monitor the printer output bin • Monitor the print quality • Clean the printer Simple Mail Trasnsfer Protocol • • • • • The protocol is very simple Uses port 25 All files are ascii text Syntax: [email protected] Mail relay: user%[email protected] • Mail Exchange (MX) – Allows mail server redirection SMTP Mail Servers • POP2, POP3 – Uses port 109 or 110 – Post Office Protocol, mail transfers to client, download all mail to the client (older protocol, replaced by): • IMAP – Uses port 143 – Internet Message Access Protocol, mail stays on server – Better for mobile (transient) clients • Webmail – uses a Web interface to access mail Mail Clients • Eudora – Commercial • Netscape Messenger – Comes with Netscape • Outlook – Comes with Windows 9x, 2000 • Webmail, Groupwise – Uses any web browser Client Setup • Client can have separate mail server and smtp server. • Mail server is where our mail is received • SMTP server is where we send our messages • The Mail server can have virus and spam filters Spamming • Mail Relaying to an off site recipient • Testing SMTP mail – abuse.net • Configuration to prevent SPAM – allow only local domain relays to internet Headers • • • • • • From Date: Subject: To: Resent-date: Resent-from: Attachments • Using mail to transfer files • Simple operation • Incompatible programs – Word for MAC vs. Word for PC – .pdf solves the compatibility problem • Dangers (viruses, trojan horses) – Executable programs that the client downloads and automatically executes Encoding Methods • Binary Files (programs, sound, video) • UUENCODE (UNIX) – one file per encode • MIME (WWW, POP, IMAP) – multiple files per encode • BinHex (Apple) – one file per encode SMTP Example 1> telnet cc.usu.edu.edu 25 2> 220 grumpy.usu.edu – ESMTP Server (PMDF V5.2-32) 1> HELO pc15.logan.tv 2> 250 grumpy.usu.edu Ok, “port 32443”@techsun.cs.usu.edu” [129.123.7.33] 1> MAIL From:<[email protected]> 2> 250 2.5.0 Address Ok. 1> RCPT To:<[email protected]> 2> 250 2.1.5 [email protected] Ok. 1> DATA 2> 354 Start Mail input; end with <CRLF>.<CRLF> 1> Date: Sat, 22 Mar 1998 13:26:31 MST 1> From: [email protected] 1>Subject: Meeting tomorrow SMTP Example cont. 1> The meeting is TOMORROW at 3:00 PM! 1> 1> . 2> 250 2.5.0 Ok 1> QUIT 2> 221 2.3.0 Bye received. Goodbye. FTP • File Transfer Protocol – User – Anonymous • GET/PUT/DEL/CWD – GUI Interface • Binary/Ascii • Hash FTP Example • requires 2 ports • telnet ftp.remotesite.com 21 – – – – – – 220 ftp.remotesite.com FTP server ready user anonymous 331 password required for anonymous password [email protected] 230 user anonymous logged in PORT 1200 FTP Example cont. • • • • PORT 129,123,7,55,4,76 200 PORT command successful pwd 257 “/export/guest/bobw” is current directory • RETR ./.login • 150 ASCII data connection for ./.login(129.123.7.55,1100)(795 bytes) • QUIT NTP • Network Time Protocol – Uses port 123 • • • • UDP (User Datagram Protocol) Atomic Clock Synchronization Multiple Servers Used for – Distributed Databases – Client/Server – Security Clock Synchronization mt mr Time Server Time Client Tround = mt + mr time = t Clock set is t + Tround/2 NNTP • Network News Transfer Protocol – Uses port 119 • Distributed Bulletin Board – Uses a tree hierarchy • Minimizes Duplicate messages/disk space • Tree based distribution • Store and Forward Web Browsers • Mosaic – More or less the first web browser • Netscape – Became extremely popular very quickly • Microsoft Internet Explorer – Plays catch up with Netscape • HotJava – Sun Microsystems Browser Web Browsers Cont. • Web Browsers can cache pages and pictures locally to speed up access • Web Browsers can use a proxy server to remotely cache pages and pictures for many systems. • The proxy can act as a firewall and IP translator. Web Servers • • • • Apache Roxen Netscape Microsoft – IIS Web Servers Cont. • Use http (hyper text transfer protocol) to create file and service access • Can have virtual servers to save IP addresses • Can have additional ports (services) • Most of the fancy stuff is done by the browser. HTML • • • • Hyper Text Markup Language Uses ascii text and commands Automatically formats text Sets up hyper links and displays pictures • Connects to services such as ftp • Start with <command> and end with </command> HTML Cont. • <BODY> • <a href=“http://www.usu.edu></a> • <a image=“fred.gif”></a> • <li>Hello</li> • </BODY> XML • eXtensible Markup Language • Extends basic HTML to aid in creating documents and document systems. • Creates access to data bases CGI’s Common Gateway Interface • Allow Web browsers to execute programs on the Web server. • Uses: Mail, finger, database, animation, sound • Found in /cgi directory in the Web page home • Are executable C, perl, java, or shell programs ASP • Active Server Pages • Similar functions to CGI’s • Can do access counters, database access and online forms (fill in the blank) PHP • Personal Home Page Tools • Language for creating Web programs • Syntax is similar to Basic Java • Developed by Sun • C++ context • Builds GUI’s (Graphical User Interfaces) • Handles animated objects on the web page Security and the WEB • WEB files must be world readable. • The WEB server may be run by root • CGI’s can be dangerous security holes. • PHP, ASP, and VBscripts can have security holes (buffer overflows) • WEB servers are searched by many search engines that broadcast your data.