Inaddr_any Post: 21798

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Special Forums IP Networking Inaddr_any Post 21798 by killerserv on Thursday 23rd of May 2002 01:53:37 AM

05-23-2002

Registered User

Im not sure clearly what your question is, but i will give a try.
INADDR_ANY has the following semantics, When receiving, a socket bound to the address receives packets from all interfaces. For example, suppose that a host has interfaces 0, 1 and 2. If a UDP socket on this host is bound using INADDR_ANY and udp port 8000, then the socket will receive all packets for port 8000 that arrive on interfaces 0, 1, or 2. If a second socket attempts to Bind to port 8000 on interface 1, the Bind will fail since the first socket already "owned'' that port/interface. When sending, a socket bound with INADDR_ANY binds to the default IP address, which is that of the lowest-numbered interface.

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LEARN ABOUT BSD

udp

UDP(4P) 																   UDP(4P)

NAME

       udp - Internet User Datagram Protocol

SYNOPSIS

       #include <sys/socket.h>
       #include <netinet/in.h>

       s = socket(AF_INET, SOCK_DGRAM, 0);

DESCRIPTION

       UDP  is	a  simple, unreliable datagram protocol which is used to support the SOCK_DGRAM abstraction for the Internet protocol family.  UDP
       sockets are connectionless, and are normally used with the sendto and recvfrom calls, though the connect(2) call may also be  used  to  fix
       the destination for future packets (in which case the recv(2) or read(2) and send(2) or write(2) system calls may be used).

       UDP  address  formats  are  identical to those used by TCP. In particular UDP provides a port identifier in addition to the normal Internet
       address format.	Note that the UDP port space is separate from the TCP port space (i.e. a UDP port may not be "connected" to a  TCP  port).
       In  addition  broadcast	packets  may be sent (assuming the underlying network supports this) by using a reserved "broadcast address"; this
       address is network interface dependent.

       Options at the IP transport level may be used with UDP; see ip(4P).

DIAGNOSTICS

       A socket operation may fail with one of the following errors returned:

       [EISCONN]      when trying to establish a connection on a socket which already has one, or when trying to send a datagram with the destina-
		      tion address specified and the socket is already connected;

       [ENOTCONN]     when trying to send a datagram, but no destination address is specified, and the socket hasn't been connected;

       [ENOBUFS]      when the system runs out of memory for an internal data structure;

       [EADDRINUSE]   when an attempt is made to create a socket with a port which has already been allocated;

       [EADDRNOTAVAIL]
		      when an attempt is made to create a socket with a network address for which no network interface exists.

SEE ALSO

       getsockopt(2), recv(2), send(2), socket(2), intro(4N), inet(4F), ip(4P)

4.2 Berkeley Distribution					   May 16, 1986 							   UDP(4P)