Web Server Administration
Chapter 9
Extending the Web Environment
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Overview
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Understand File Transfer Protocol (FTP)
services
Install and configure an VSFTP server in Linux
Install and configure FTP client on Linux
Understand News servers
Configure remote access to a server
Understand streaming media servers
Understand e-commerce software
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Understanding FTP Services
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FTP is used to transfer files from a server to a
client (download) and transfer files from a
client to a server (upload)
FTP client is the browser
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Also command-line and GUI clients
FTP servers can operate as anonymous
servers or they can require a valid logon
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FTP servers are not secure; user names and
passwords are not sent encrypted
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Understanding FTP Services
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FTP uses 2 ports: Data port & Control port
Control port (port 21) – client connects
originally
Data port (port 20) – client connects for data
2 types:
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Active FTP
Passive FTP (data port is not port 20)
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Client initiates both port connections
Most web based ftp clients use passive
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Active FTP
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Step 1, the client's command port
contacts the server's command port
and sends the command PORT 1027.
Step 2, The server then sends an ACK
back to the client's command port.
Step 3 the server initiates a connection
on its local data port to the data port
the client specified earlier.
Step 4, Finally, the client sends an ACK
back.
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Passive FTP
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Step 1, the client contacts the server on
the command port and issues the PASV
command.
Step 2, The server then replies with
PORT 2024, telling the client which port
it is listening to for the data connection.
Step 3 the client then initiates the data
connection from its data port to the
specified server data port.
Step 4, the server sends back an ACK.
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Communicating with FTP
Command
Description
Example
ftp host
Initiates a connection to FTP server
ftp 192.168.0.100
open host
Once the FTP client has been started,
opens a connection
open 192.168.0.100
close
Closes the connection but does not
exit the FTP client
close
quit or
bye
Closes the connection and exits the
FTP client
bye
ls
filenames
Displays filenames and can use
wildcards
ls *.rpm
dir
filenames
Displays the long listing of files and
their properties, such as the size and
date the file was created
dir *.rpm
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Communicating with FTP
Command
Description
Example
binary
Transfer files in binary mode
binary
ascii
Transfer files in text mode
ascii
get filename
Downloads a single file
get test.rpm
put filename
Uploads a single file
put testapp.zip
Mget filenames Downloads multiple files;
used with wildcards
mget sendmail*.rpm
mput filenames Uploads multiple files;
used with wildcards
mput *.tif
prompt no
Stops prompting for each file
when used before you use
mget or mput
prompt no
prompt
Starts prompting
prompt
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Communicating with FTP
Command
Description
Example
hash
Displays a hash symbol as files
are being downloaded
hash
cd directory
Moves to another directory on
the FTP server
cd /software
lcd directory
Moves to another directory on
the client
lcd /docs
pwd
Displays the current directory on
the server
pwd
help command
Finds very brief help on FTP
commands; if used without a
reference to a command, it
will give you a list of
commands available
help mget
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Understanding News Servers
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News servers allow threaded discussions
You post messages in a newsgroup
A newsgroup focuses on a single topic
There are more than 40,000 public
newsgroups
There are hundreds of gigabytes of
information generated per day
News servers can be set up for use within an
organization
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Configuring Telnet in Linux
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By default, telnet is installed but not enabled
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Telnet should not be used in a non-secure
environment such as over the Internet because user
names and passwords are not encrypted
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chkconfig telnet on
service xinetd restart
ssh is a secure replacement (described in Chapter 10)
You cannot log on as root
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However, you can log on as another user and "su root"
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Understanding Streaming
Media Services
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Used to transfer video and audio
By default, UDP is used
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Although TCP and HTTP can be used because of
firewall issues in an organization
No single standard exists as is true with
SMTP, HTTP, POP3, and others
Broadcast methods
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unicast – each packet is sent individually to each
client
multicast – each packet is sent to many clients
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Understanding Streaming
Media Services
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Helix Universal Server from Real
Networks is popular
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Recognizes both Real Networks protocols
(RTSP, PNA) and the Microsoft protocol
(MMS)
Windows Media Services is a Windows
component
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Creates a folder called \ASFRoot to store
Advanced Streaming Format (ASF) files
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Understanding E-Commerce
Servers
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Can be as simple as a product list and a
shopping cart
Can be as complex as amazon.com or
dell.com
Microsoft Commerce Server is an add-on to
IIS
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Incorporates a number of features required for a
typical e-commerce site
Highly customizable
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Summary
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Use FTP to transfer files
You use News servers to set up threaded
discussions on a variety of topics
Telnet and Windows Terminal Services allow
you to remotely administer a server
Streaming media servers are used for video
and audio
E-commerce servers focus on selling and in
general, communicating with customers
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