Transcript How Clients and Servers Work Together

How Clients and Servers
Work Together
Objectives
• Learn about the interaction of clients and
servers
• Explore the features and functions of Web
servers
Understanding How Clients and
Servers Interact
• A server can be software that provides a
service to other software or the computer
on which the server software is running.
• Consider a server as a software
application that must be installed and
managed by someone with the title of
system administrator, network
administrator, or, for Web servers,
Webmaster.
User Interfaces: GUI Versus
Command-Driven
• When you use a command-driven
interface, you type commands into a user
interface to perform a task and achieve a
desired result.
• In contrast to a command-driven interface,
a graphical user interface (GUI) has
icons or menus that you can select to
perform a function or run a program.
User Interfaces: GUI Versus
Command-Driven (Continued)
• Applications that run on computers and
servers can also be controlled by
configuration or initialization files.
• An initialization file (INI file) is an ASCII
text file with a .ini file extension.
Client/Server Sessions
• Transmission
Control Protocol
(TCP) manages
the three-way
handshake that
establishes a
session to be used
by application
protocols, such as
HTTP or FTP.
Tracking Information in Log
Files
• Servers and client applications often track
information about their activities in log
files.
• These are text files that administrators can
use to troubleshoot problems with the
software, to track activities to analyze
traffic patterns or user preferences, or to
look for clues indicating that hackers are
using the server.
All-in-One Clients
• As the number of applications that use the
Internet grows, the need for client software on
computers to use these applications also grows.
• One solution to the growing number of Internet
applications is an all-in-one client or universal
client.
• These clients can handle several applications
and adjust appropriately, changing buttons and
functions to accommodate each application.
• Microsoft Internet Explorer is a good example of
an all-in-one client.
Exploring the Features and
Functions of Web Servers
• A wide variety of Web servers are
available, many of which you can
download for free.
• Some popular Web servers include the
following:
– Apache Web Server
– Microsoft Internet Information Services (IIS)
– Border Manager
– Netscape Enterprise Server (NES)
Ability to Support Virtual Servers
and Virtual Hosts
• A Web server should be able to support
virtual servers and virtual hosting.
• Most virtual hosts handle multiple domain
names on the same server by having the
Uniform Resource Locator (URL) serve as
a path to a file.
Protocols Supported
• All Web servers support HTTP, and some
also support FTP so developers can send
files to the site from remote locations.
• If you want to use your Web server for email, the server must support e-mail
protocols.
Access Control
• Based on the user’s IP address or user ID,
access control allows the Web server to limit to
which files a user can read or write. User Ids are
associated with passwords to verify a user’s
identity.
• Another method of access control is changing
the port at which a server is listening.
• Port 80 is the default port for Web servers.
• Apache Web Server controls access to its
resources via a process known as
authentication, which requires a user to enter a
valid user ID and password to access a Web
site.
Access Control (Continued)
Encrypting Protocols
• A secure protocol used by Web servers is
SSL (Secure Sockets Layer).
• When you see a URL with https: at the
beginning instead of http:, you know that
this Web server is using the SSL protocol
for security.
Chroot Mode
• Chroot mode restricts the portion of the
file system that the server occupies.
• Running in chroot mode offers security
because all private files can be kept
outside of the server area.
Server Side Scripting
• A script is a short list of instructions that
certain software can perform.
• The instructions must be written in a
format called a scripting language.
• Popular scripting languages include Perl,
VBScript, and JavaScript.
Standard CGI-Based Scripts
• Common Gateway Interface (CGI) is the
set of specifications that defines how a
Web server passes a Web user’s input to
an application program running on the
server, receives a response, and passes
data back to the user.
• One advantage of CGI scripts is that they
are consistent among operating systems.
Server-Side Include (SSI)
• Server-Side Include (SSI) is a simple
form of scripting that allows you to include
variable values in HTML code before it is
sent to the browser.
• SSI scripts insert a line in the HTML file
that indicates a variable value needs to be
entered before the file is sent to the
browser.
Database Interfaces
• Before selecting a Web server or a virtual
hosting service, find out what databases
the server supports and what tools can
exchange information with the database.
• Popular databases are MS Access,
MySQL, Oracle, and SQL Server.
Ability to Monitor Performance
• Microsoft IIS uses Performance Monitor, a
program that comes with Windows Server
2003 and Windows 2000 Server, to
monitor performance.
• Other utility programs are Microsoft Web
Capacity Analysis Tool (WCAT) and Server
Check Pro by NetMechanic.
Summary
• A server can be software that provides a service
to other software or the computer on which the
server software is running.
• TCP creates sessions that application protocols,
such as HTTP and FTP, can use.
• Apache Web Server by the Apache Software
Foundation is a common Web server that runs
on a UNIX or Windows platform.