3 types of services in linux

Hi Pravin,

You asked about services written in c++. I googled and found that "service" has a specific meaning in linux/unix. http://www.comptechdoc.org/os/linux/howlinuxworks/linux_hlservices.html describes 3 types of services --

* A one time only program run at bootup to provide a function to the system such as kudzu, or keytable.
* A program run as a daemon upon startup that provides system services such as gpm, autofs, cron, and atd.
* A program run as a daemon upon startup that provides networking services such as dhcpd, bootparamd, arpwatch, gated, and httpd.

The way I see it (no expert here), the standard *nix network daemons provide a Generic functionality at the System level - like DHCP, DNS, http, FTP, mail etc. In contrast, a custom c++ engine used in finance has site-specific business logic. It often binds to a standard network port. Alternatively it may use database, RPC, (Corba?), MOM, or some proprietary protocol for network communication. In some cases the communication is entirely inter-process -- no networking. Just IPC like shared memory, named pipes or unix domain sockets. I don't know which communication mode is dominant. I guess shared memory and MOM are popular.