4.3BSD - /usr/man/cat4/inet.0

INET(4F)                                                              INET(4F)


NAME
       inet - Internet protocol family

SYNOPSIS
       #include <sys/types.h>
       #include <netinet/in.h>

DESCRIPTION
       The  Internet protocol family is a collection of protocols layered atop
       the Internet Protocol (IP) transport layer, and utilizing the  Internet
       address  format.  The Internet family provides protocol support for the
       SOCK_STREAM, SOCK_DGRAM, and SOCK_RAW socket types; the SOCK_RAW inter‐
       face provides access to the IP protocol.

ADDRESSING
       Internet addresses are four byte quantities, stored in network standard
       format (on the VAX these are word and byte reversed).  The include file
       <netinet/in.h> defines this address as a discriminated union.

       Sockets  bound  to  the  Internet protocol family utilize the following
       addressing structure,

       struct sockaddr_in {
              short     sin_family;
              u_short   sin_port;
              struct    in_addr sin_addr;
              char      sin_zero[8];
       };

       Sockets may be created with the  local  address  INADDR_ANY  to  effect
       “wildcard”  matching on incoming messages.  The address in a connect(2)
       or sendto(2) call may be given as INADDR_ANY  to  mean  ‘‘this  host.’’
       The  distinguished  address  INADDR_BROADCAST is allowed as a shorthand
       for the broadcast address on the primary network if the  first  network
       configured supports broadcast.

PROTOCOLS
       The Internet protocol family is comprised of the IP transport protocol,
       Internet Control Message Protocol (ICMP), Transmission Control Protocol
       (TCP),  and  User  Datagram Protocol (UDP).  TCP is used to support the
       SOCK_STREAM abstraction while UDP is used  to  support  the  SOCK_DGRAM
       abstraction.   A raw interface to IP is available by creating an Inter‐
       net socket of type SOCK_RAW.  The ICMP message protocol  is  accessible
       from a raw socket.

       The  32-bit  Internet address contains both network and host parts.  It
       is frequency-encoded; the most-significant bit  is  clear  in  Class  A
       addresses,  in  which  the  high-order  8  bits are the network number.
       Class B addresses use the high-order 16 bits as the network field,  and
       Class  C addresses have a 24-bit network part.  Sites with a cluster of
       local networks and a connection to the DARPA Internet may chose to  use
       a  single  network number for the cluster; this is done by using subnet
       addressing.  The local (host) portion of the address is further  subdi‐
       vided into subnet and host parts.  Within a subnet, each subnet appears
       to be an individual network; externally, the entire cluster appears  to
       be  a  single,  uniform  network requiring only a single routing entry.
       Subnet addressing is enabled and examined  by  the  following  ioctl(2)
       commands  on  a  datagram  socket in the Internet domain; they have the
       same form as the SIOCIFADDR command (see intro(4N)).


       SIOCSIFNETMASK      Set  interface  network  mask.   The  network  mask
                           defines  the  network  part  of  the address; if it
                           contains more of the address than the address  type
                           would indicate, then subnets are in use.

       SIOCGIFNETMASK      Get interface network mask.

SEE ALSO
       ioctl(2), socket(2), intro(4N), tcp(4P), udp(4P), ip(4P), icmp(4P)

       An Introductory 4.3BSD Interprocess Communication Tutorial (PS1:7).

       An Advanced 4.3BSD Interprocess Communication Tutorial (PS1:8).

CAVEAT
       The Internet protocol support is subject to change as the Internet pro‐
       tocols develop.  Users should not depend  on  details  of  the  current
       implementation, but rather the services exported.


4.2 Berkeley Distribution        June 1, 1986                         INET(4F)