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Netdb is an unit DNS resolving under *nix, grouped in the larger fcl-net package. It forms the basis of FCL level DNS resolving which is truly platform independent.
After being broken for a while, after 1.9.8 some serious fixes were made, and the IPV4 calls should be in at least usable form for FreeBSD/Linux/Darwin on x86 and PowerPC.
The most common misconception about netdb is that gethostbyname is a direct alternative for the libc call with the same name (which resolves a host). However, the netdb call gethostbyname really only checks /etc/hosts, and netdb resolvename only checks the DNS servers listed in /etc/resolv.conf.
This has the following consequences:
- it takes two calls to resolve a name (one to check hosts, one to check DNS) (in other words testdns and testhost code is both needed)
- the LOOKUP (OpenBSD) command in resolv.conf is not processed.
- Other forms of resolving than /etc/hosts and (like YP/Yellow Pages) are not supported.
- Setting FPC_USE_LIBC doesn't have any consequences yet, the non-libc code will still be used.
Note that fcl-net also contains a straight libc using resolve header, cnetdb since FPC 2.2.4.