ICMP(4P)                                                              ICMP(4P)



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 _p_r_o_t_o parameter
       to the socket call to create an ICMP socket is obtained from  _g_e_t_p_r_o_t_o_‐
       _b_y_n_a_m_e(3N).   ICMP  sockets  are  connectionless, and are normally used
       with the _s_e_n_d_t_o and _r_e_c_v_f_r_o_m calls, though the _c_o_n_n_e_c_t(2) call may also
       be  used  to  fix the destination for future packets (in which case the
       _r_e_a_d(2) or _r_e_c_v(2) and _w_r_i_t_e(2) or _s_e_n_d(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  con‐
                      nected;

       [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  net‐
                      work address for which no network interface exists.

SEE ALSO
       send(2), recv(2), intro(4N), inet(4F), ip(4P)



4.3 Berkeley Distribution        May 16, 1986                         ICMP(4P)