Virtual Private Server User Guide

Network Servers and Server Applications

Chapter 3   Network Servers and Server 

Applications

A network service allows remote users to connect to your VPS server to access 

information or perform certain functions. You are already familiar with the SSH, 

Telnet, and other network services, which allow you to log into your server, and 

you have probably used other network services such as FTP, e mail or the HTTP 

(Web) services. 

Network services are provided by server applications, which are also referred to 

as daemons. A daemon is a program that listens on a network port, accepts 

connections, and services requests for access or information. For example, when 

someone sends e mail to a user account on your server, it is the Sendmail server 

application that receives the mail and prepares it to be picked up by the user. 

When someone visits your Web site, it is the Apache Web server application that 

receives the request and returns the appropriate page to the visitor. 

All server applications are run in one of two ways: as a standalone application or 

as an application invoked (spawned) by the xinetd application. Applications that 

run in standalone mode are constantly running, listening for requests. Applications 

invoked through xinetd are executed only when a service is requested, and 

terminate when the request has been fulfilled. In general, applications are run as 

standalone daemons when speed is critical or high traffic is expected. Likewise, 

the applications spawned through xinetd are done so for efficiency and to reduce 

overhead and resource drain on the server.

The following table displays the basic network services that are provided by 

default on your server, as well as the server applications that power these 

services:

Technical Training Department

August 2004

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