Server and Client: A server is a computer running software that answers requests for documents and other data. The programs that request and display the documents are called clients. Typically, the server is a remote machine and the client is the user's local machine. The terms "server-side" and "client-side" refer to which program is doing the processing.

Web Server: A program that handles requests for information from browsers. It allows HTML documents to be linked across a network. Browsers (clients) and servers communicate using Hypertext Transfer Protocol (HTTP). Web servers answer requests from browsers to retrieve documents or execute programs (e.g. CGI scripts) and return the documents or results.

• Server: stores and processes information
• Client: requests and displays information
• Protocol: connects the server and client (e.g. HTTP)
• HTTP process: the client makes a request to server using HTTP (in the form of a URL), the server processes the request and using HTTP sends the HTML document to the client

Domain Name Service (DNS): DNS is an Internet service that translates domain names (e.g. www.clatsopdesign.com) into IP addresses (e.g. 68.116.36.144 ). Computers on the internet use the numbers to communicate; people use the names to navigate. DNS makes this possible. There are thousands of DNS computers on the internet sharing information about the name and numbers they know about. When you register a domain you need to specify who your DNS servers are. The DNS servers are usually provided to you by the company that is hosting your website. These name servers tell internet users how to find your website or email.

The DNS system is, in fact, its own network. If one DNS server doesn't know how to translate a particular domain name, it asks another one, and so on, until the correct IP address is returned. For example, if you want to navigate to www.clatsopdesign.com. The browser makes a request of your ISP's DNS server (1) "do you know the number for this website?" If it does, it will tell your browser what it is and you connect directly to the Website Server (3). If the ISP's DNS server doesn't know, it will ask the website owner's DNS server for the number (2). Then it connects to the website server (3). (Adapted from Andrea Butterworth at Bravenet.com)

Web Server Software: A majority of web servers run on Unix systems although some run on Windows and Macintosh systems. Popular servers include NCSA Server, Apache, CERN, Netscape Servers, Internet Information Server(IIS), W3C Jigsaw.

• Apache Web Server: the leading UNIX Web server (also runs on Windows NT). It is availabe free and supports many server-side programming tools including Perl, Java Servlet and Secure Sockets Layer.
• Internet Information Server (IIS): extends Windows NT Server with Internet and Intranet capabilities including World Wide Web and FTP service, administrative, database and security tools.

File organization: Although most web developers deal with client-side issues it is necessary to understand basic server issues to upload files and link to scripts.

• Directory Structure: directories (or folders) are organized into a hierarchical (tree) structure.
• Root Directory: the topmost level of the hierarchy.
• Pathname: the location (or address) of a file in the hierarchy. Absolute pathnames begin at the root (e.g. /users/bigdog/html/index.html), relative pathnames are with respect to the current directory (e.g. ../cgi-bin/mailform.cgi)
• Naming Conventions: use consistent and established naming conventions for files and folders (e.g. avoid spaces and special characters such as ?, *, #). Use proper suffixes (e.g. .html for HTML documents and .gif for gif files). Filenames are case sensitive, use case consistently.

Unix: It may be useful to know a little bit of Unix to better communicate with the server. Unix commands have the format: command option(s) filename(s). A few examples (word in brackets are replaced with actual values):

• change directory: cd [pathname]
• print working directory: pwd
• copy file: cp [oldname] [newname]
• rename file (move): mv [source] [target]
• list directory: ls [option(s)]
• make new directory: mkdir [dirname]
• delete (remove) file: rm [filename]
• changing permissions: chmod [setting] [filename]

Communicating with the server: There are three basic methods of communicating with a server: HTML editor, FTP program or telnet session.

• HTML Editor: Using an HTML editor is usually the easiest approach to transfer files and provides numerous tools such as drag and drop interface, link checking and file synchronization.
• FTP Program: There are many FTP programs available for all platforms (e.g. WS_FTP and Fetch). Most browsers can also function as FTP programs.
• Telnet: Telnet is a terminal emulation protocol that allows a user to log in to a remote system over a network. It uses a character-based command line interface.

File Transfer Protocol (FTP): HTML documents, graphics, media and programs must be uploaded from the local computer to the server over a network. Whether using an HTML editor, FTP program or telnet, the usual method of doing this is by the File Transfer Protocol.

FTP Process: In order to transfer files to a server an account with proper permissions must be set up on the server (this is done by the server administrator). The usual process to upload files consists of the following steps:

• Launch the FTP program and open a connection with the server (this requires the name of server, account name and password).
• Locate directory on server. New directories can be created and existing files and directories can be deleted as necessary.
• Set transfer mode (ASCII, Binary or Auto).
• Upload the files. FTP uses the terminology "put" (uploading files to server) and "get" (downloading files to local computer).
• Disconnect from server and exit FTP program.

Downloading files: Browsers can download files from the server using FTP. One way to do this is to specify FTP in a link: <a href="ftp://domain.com/docs/filename.zip">download filename</a>

Server-Side Technologies: Technologies that increase the capabilities of the server beyond delivering standard HTML documents. There are many languages taht can be used for server-side programming.

• CGI scripts: programs (typically Perl, .pl or .cgi) that reside on the server (usually in cgi-bin directory) and use the Common Gateway Interface to communicate with the HTTP server (e.g. form processors).
• Server-Side Includes (SSI): commands embedded in HTML documents that instruct server to dynamically insert data or execute CGI scripts before sending document to browser (often use .shtml extension).
• Java Servlets: java application programs that extend the functionality of the server. Note Java Applets are client-side programs
• Secure Sockets Layer (SSL): a protocol for encrypting transmission of data for security. With SSL URLs use https instead of http, for example https://domain.com/file.html
• Active Server Pages (ASP): text files (.asp) containing HTML and scripting code (typically VBScript) to be executed by the server. Require Microsoft server (IIS).

Server Side Includes: code in an HTML document that is replaced with data by the server before sending the document to the browser (view source shows the data as normal HTML, hiding the SSI commands). SSI is often used in combination with CGI scripts to provide more powerful dynamic page generation. SSI commands are server dependent.

Cookies: small text files saved on the client machine used to maintain state information for the client (e.g. user preferences, last access time, session tracking). The cookie is sent back to the server whenever the client requests a particular web page. Cookies are written and read by CGI scripts, ASP or Servlets. Cookies are limited to small amounts of text data. Internet Explorer stores cookies in the Windows/Temporary Internet Files folder, Netscape stores cookies in the "cookies.txt" file in the Netscape folder. Cookies can be turned off or limited by setting browser options.