icmp(ADMP)                    06 January 1993                     icmp(ADMP)


 Name

    icmp - Internet Control Message Protocol

 Syntax

    programmer's interface:
    #include  <sys/socket.h>
    #include  <netinet/in.h>

    s = socket(AFINET, SOCKRAW, IPPROTOICMP);

 Description

    ICMP is the error and control message (or device) 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 (See getprotoent(SLIB).)  ICMP sockets are connectionless,
    and are normally used with the sendto and recvfrom calls; the
    connect(SSC) call may also be used to fix the destination for future
    packets (in which case the read(S) or recv(SSC) and write(S) or send(SSC)
    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 con-
                       nected;

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

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


 Files

    /dev/inet/icmp

 See also

    inet(ADMP), intro(ADMP), ip(ADMP), recv(SSC), send(SSC)