ICMP(7P)                                                              ICMP(7P)


NAME
     icmp - Internet Control Message Protocol

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

     s = socket(AF_INET, SOCK_RAW, proto);

DESCRIPTION
     ICMP is the error and control message protocol used by IP and the
     Internet protocol family.  It may be accessed through a "raw socket" for
     network monitoring and diagnostic functions.  The proto parameter to the
     socket call to create an ICMP socket is obtained from getprotobyname(3N).
     ICMP 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 read(2) or recv(2)
     and write(2) or send(2) system calls may be used).

     Outgoing packets automatically have an IP header prepended to them (based
     on the destination address).  Incoming packets are received with the IP
     header and options intact.

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 destination 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;

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

SEE ALSO
     send(2), recv(2), intro(3), inet(7F), ip(7P)


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