Socket network functions

Socket network functions allow application programs to obtain information from the host, protocol, service, and network files.

The information can be accessed by name or by address, or by sequential access of the file. These network functions (or routines) are required when setting up communications between programs that run across networks, and thus are not used by AF_UNIX sockets.

The routines are as follows:

Map host names to network addresses.
Map network names to network numbers.
Map protocol names to protocol numbers.
Map service names to port numbers.
Convert the byte order of Internet network addresses.
Convert IP address and dotted decimal notation.

Included in the network routines is a group of routines called resolver routines. These routines make, send, and interpret packets for name servers in the Internet domain and are also used to do name resolution. The resolver routines normally get called by gethostbyname(), gethostbyaddr(), getnameinfo(), and getaddrinfo() but can be called directly. Primarily resolver routines are used for accessing Domain Name System (DNS) through socket application.