10.3.1.1. Standalone server

Offering a service to users can be approached in two ways. A daemon or service can run in standalone mode, or it can be dependent on another service to be activated.

Network services that are heavily and/or continuously used, usually run in the standalone mode: they are independent program daemons that are always running. They are most likely started up at system boot time, and they wait for requests on the specific connection points or ports for which they are set up to listen. When a request comes, it is processed, and the listening continues until the next request. A web server is a typical example: you want it to be available 24 hours a day, and if it is too busy it should create more listening instances to serve simultaneous users. Other examples are the large software archives such as Sourceforge or your Tucows mirror, which must handle thousands of FTP requests per day.

An example of a standalone network service on your home computer might be the named (name daemon), a caching name server. Standalone services have their own processes running, you can check any time using ps:

bob:~> ps auxw | grep named
named   908  0.0  1.0 14876 5108 ?   S  Mar14  0:07 named -u named

However, there are some services that you can use on your PC, even if there is no server process running for that services. Examples could be the FTP service, the secure copy service or the finger service. Those services have the Internet Daemon (inetd) listening in their place.