Internet Services Some samples: , login, file transfer, news document distribution, web services, etc…

TCP Port: 25 uses Simple Mail Transfer Protocol Clients: mailx, pegasus, MS-outlook, Netscape messenger Servers: Sendmail (Unix), MS-Exchange (NT), Netscape Messaging Server (Unix, NT)

Terminal Emulation Port: 23 (uses Telnet Protocol) Clients: telnet Servers: telnetd Port: 22 Clients: ssh Servers: sshd

File Transfer Uses File Transfer Protocol Port: 21 Clients: ftp Servers: ftpd (Unix), IIS (NT and Windows)

News Uses Network News Transfer Protocol Port: 119 Clients: MS-Outlook, Netscape Collabra Servers: nntpd(Unix)

Electronic Documents Gopher Protocol Port: 70 Clients: wingopher Servers: IIS

Web Services Uses HTML Protocols port: 80 Clients: Netscape Navigator, MS IE Servers: IIS for Windows Platform, Apache Tomcat for Java Platform

With each of the preceding, multiple clients may communicate with a single server

The normal usage of this application is to create a message for another user on a local or remote computer system and have it delivered electronically. An example of “push” delivery

e.g. mail Subject: How is the Project? Message Hi, I got your last message etc

The message is sent from the originating mail serving application to the destination mail serving application via a route that may pass through many mail servers on its way.

Mail servers Mail clients

Received: from (2) ALPHA8.MONASH.EDU.AU by (1) silas.monash.edu.au (8.9.3/ /16Feb AM) id XAA ; Tue, 23 Apr :50: (EST) Received: from blammo.monash.edu.au ([ ]) by (3) vaxh.monash.edu.au (PMDF V #39306) with ESMTP id for Tue, 23 Apr :50: Received: from blammo (unknown [ ]) by (4) localhost (Postfix) with ESMTP id C002 for ; Tue, 23 Apr :50: (/etc/localtime) Received: from mail1.monash.edu.au (bigted.monash.edu.au [ ]) by (5) blammo.monash.edu.au (Postfix) with ESMTP id 14A8512C002 for ; Tue, 23 Apr :50: (EST) Received: from ALPHA1.MONASH.EDU.AU ([ ]) by (6) mail1.monash.edu.au (Netscape Messaging Server 4.15) with ESMTP id GV0X4I00.NBA for ; Tue, 23 Apr :50: SMTP Headers

Received: from (8) blammo.monash.edu.au ([ ]) by (7) vaxc.monash.edu.au (PMDF V6.1 #39306) with ESMTP id for (ORCPT Tue, 23 Apr :50: Received: from blammo (unknown [ ]) by localhost (Postfix) with ESMTP id 762F512C002 for ; Tue, 23 Apr :50: (/etc/localtime) Received: from (9) mail021.syd.optusnet.com.au (mail021.syd.optusnet.com.au [ ]) by blammo.monash.edu.au (Postfix) with ESMTP id 1F4AE12C002 for ; Tue, 23 Apr :50: (EST) Received: from CO A (10) (c16494.frank1.vic.optusnet.com.au [ ]) SMTP Headers

by mail021.syd.optusnet.com.au (8.11.1/8.11.1) with SMTP id g3NDoRi15920 for ; Tue, 23 Apr :50: Date: Tue, 23 Apr :51: From: Patrik From: Patrik Subject: Questions To: Message-id: Message-id: MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V X-Mailer: Microsoft Outlook IMO, Build ( ) Content-type: MULTIPART/MIXED; BOUNDARY="Boundary_(ID_DI+xGCWXZlChun9D5NMJlw)" Importance: Normal X-Priority: 3 (Normal) X-MSMail-priority: Normal Parts/Attachments: SMTP Headers

SMTP Model User Agent Local MTA Processing Queue MTA RelayLocal MTA Mailboxes User Agent

The SMTP Model MTA: A mail transfer agent exchanges mail over a TCP/IP connection System administrator is responsible for setting up the MTA SMTP defines a MTA that implements a system based upon the spooling of messages.

SMTP First proposed in RFC821 Later updated in RFC822 – replaced X.400 Commands HELO client identifies itself MAIL/RCPT identifies originator and recipient DATA for sending the contents of the mail QUIT terminates the mail exchange RSET aborts a transfer and resets both the ends VRFY to verify the address without actually sending NOOP forces server to respond with OK EXPN expands a mailing list TURN lets client and server switch roles

Mailing Lists To send mail to a group of users, mailing lists are often used. A mail server is needed to distribute the mail messages to members of a mailing list. List can be manually created, or may be automatically maintained.

Mailing Lists Listservers maintaining automated lists receive mail messages from new list members requesting that they be added to the list. eg. subscribe cse3153 Mailing Lists List members can also remove themselves from the list. eg. unsubscribe cse3153 Messages will be sent to all members of the list when is sent to the listname address on the computer that is hosting the list. eg.

Terminal Connectivity Allows remote users to log into computers that are attached to the network. Users can be located anywhere that there is a network connection. As if they were sitting at a terminal that was physically attached to that computer.

Moving files from one computer To another over the Internet FTP Assign1.doc COMPUTER A FTP Server COMPUTER B FTP Client Moving files from one computer To another over the Internet File Transfer

Anonymous ftp To use ftp, a user normally must identify themselves with a username and password. Having accounts for all possible users is impractical. An anonymous user account is maintained on many ftp servers.

Anonymous ftp The anonymous account is restricted to certain areas of the server and will normally have restricted privileges (e.g. may only be permitted to read and not write). Most systems require the user's address to be typed instead of a password.

Anonymous ftp Many ftp servers use the account ftp (its easier to type). Most WWW browsers support ftp as a built in function making it easy to use file transfer

News A network of news servers around the Internet implements the Network News Transfer Protocol (NNTP). These systems support a special-interest group type of information service.

News Messages can be posted to a news group and will then be broadcast to all news servers over a period of time.

News News messages can be read by anyone using a news client that is attached to a news server. Most WWW browsers have NNTP plug-in applications

HTML Hyper Text Markup Language a simple markup language used to create hypertext documents that are portable from one platform to another

HTML HTML documents are SGML documents ISO Standard 8879:1986 Information Processing Text and Office Systems; Standard Generalized Markup Language (SGML)

HTML HTML describes the structure and organization of a document It only suggests appropriate presentations of the document when processed Tags define the start and end of headings, paragraphs, lists, character highlighting and links

URL - Uniform Resource Locator A link or pointer to an object or resource Could be a file, a HTML document on a remote system etc

HTML HTML was developed as part of the World Wide Web - a concept that was initiated at the CERN Laboratories (European Particle Physics Laboratories) Web sites have home pages the first point of access These point to other pages via URLs hypertext pointing to address of the next page

Browsers Applications that connect to WWW servers Send requests to the servers and receive responses in the form of web pages. NCSA Mosaic, Lynx, Internet Explorer, Netscape Navigator.

HTTPD Administration Ref: Virtual directory structure Directory Indexing Security Access control and user authentication Secure server chroot server Kereberos, MD5 authentications Image maps CGI Configurations Virtual Hosting Logfile rotations Starting, stopping, and restarting the daemon Multiple DirectoryIndex KeepAlive Redirect Directives Server-side includes