Service applications take requests from client applications, process those requests, and return information to the client applications. They typically run in the background, without much user input.
Windows services, known also as NT services, enable you to create long-running executable applications that run in their own Windows sessions. These services can be automatically started when the computer boots, can be paused and restarted, and do not show any user interface.
Service Applications Using DelphiHere's a list of tutorials and articles dealing with Windows Service Applications and their implementation in Delphi:
Tutorial for making a Service Application using Delphi
In this tutorial the following topics will be covered: Create a service, Install and Uninstall the service application, Make the service do something, Debugging the service application, Using the TService.LogMessage method, Sample code for a service application, FAQ.
Creating a Windows Service in Delphi
"Why would you need a service application? Well, if you have a networked system that is on 24/7, and you want to monitor the amount of resources used by a certain application, then a service is the best way to do it. Similarly, if you write software that requires updates from time to time, you can create a service that will look for those updates and download them. So, service applications have a lot of advantages."
Creating NT services in Delphi
"How can you run an application without having it run by a user who must be checked in? Run it as a service. This article shows you how to run a Delphi program as a service under NT."
Starting and stopping a Service
When installing certain types of programs it maybe necessary to restart related services to avoid conflicts.
Getting a list of installed services
Want to get a list of active, inactive or all Windows services?
Check the Status of a Service
QueryServiceStatus, OpenSCManager, OpenService...