recv(3N)                NETWORK FUNCTIONS                recv(3N)



NAME
     recv, recvfrom, recvmsg - receive a message from a socket

SYNOPSIS
     #include <sys/types.h>
     #include <sys/socket.h>

     int recv(s, buf, len, flags)
     int s;
     char *buf;
     int len, flags;

     int recvfrom(s, buf, len, flags, from, fromlen)
     int s;
     char *buf;
     int len, flags;
     struct sockaddr *from;
     int *fromlen;

     int recvmsg(s, msg, flags)
     int s;
     struct msghdr *msg;
     int flags;

DESCRIPTION
     s is a socket created with socket(3N).  recv(),  recvfrom(),
     and  recvmsg()  are  used  to  receive messages from another
     socket.  recv() may be used only on a connected socket  (see
     connect(3N)),  while recvfrom() and recvmsg() may be used to
     receive data on a socket whether it is in a connected  state
     or not.

     If from is not a NULL pointer, the  source  address  of  the
     message  is filled in.  fromlen is a value-result parameter,
     initialized to the size of the buffer associated with  from,
     and  modified  on  return to indicate the actual size of the
     address  stored  there.   The  length  of  the  message   is
     returned.   If  a message is too long to fit in the supplied
     buffer, excess bytes may be discarded depending on the  type
     of socket the message is received from (see socket(3N)).

     If no messages are available at the socket, the receive call
     waits  for  a  message  to arrive, unless the socket is non-
     blocking (see fcntl(2)) in which case -1  is  returned  with
     the external variable errno set to EWOULDBLOCK.

     The select() call may be used to determine  when  more  data
     arrives.

     The flags parameter is formed by ORing one or  more  of  the
     following:




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recv(3N)                NETWORK FUNCTIONS                recv(3N)



     MSGOOB   Read any out-of-band data present  on  the  socket
               rather than the regular in-band data.

     MSGPEEK  Peek at the data present on the socket;  the  data
               is  returned,  but  not consumed, so that a subse-
               quent receive operation will see the same data.

     The recvmsg() call uses a msghdr structure to  minimize  the
     number  of  directly supplied parameters.  This structure is
     defined in /usr/include/sys/socket.h and includes  the  fol-
     lowing members:

          caddr_t      msg_name;         /* optional address */
          int          msg_namelen;      /* size of address */
          struct iovec *msg_iov;         /* scatter/gather array */
          int          msg_iovlen;       /* # elements in msg_iov */
          caddr_t      msg_accrights;    /* access rights sent/received */
          int          msg_accrightslen;

     Here  msgname  and  msgnamelen  specify  the   destination
     address  if the socket is unconnected; msgname may be given
     as a NULL pointer if no names are desired or required.   The
     msgiov  and  msgiovlen  describe  the scatter-gather loca-
     tions, as described in read(2).  A  buffer  to  receive  any
     access  rights  sent  along with the message is specified in
     msgaccrights, which has length msgaccrightslen.

RETURN VALUE
     These calls return the number of bytes received, or -1 if an
     error occurred.

ERRORS
     The calls fail if:

     EBADF               s is an invalid descriptor.

     ENOTSOCK            s is a descriptor  for  a  file,  not  a
                         socket.

     EINTR               The   operation   was   interrupted   by
                         delivery of a signal before any data was
                         available to be received.

     EWOULDBLOCK         The socket is  marked  non-blocking  and
                         the requested operation would block.

     ENOMEM              There  was  insufficient   user   memory
                         available for the operation to complete.

     ENOSR               There were insufficient STREAMS resouces
                         available for the operation to complete.




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recv(3N)                NETWORK FUNCTIONS                recv(3N)



SEE ALSO
     connect(3N), fcntl(2),  getsockopt(3N),  ioctl(2),  read(2),
     send(3N), socket(3N).




















































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