2.11BSD#431 - /usr/man/cat2/sendmsg.0

SEND(2)             UNIX Programmer's Manual		  SEND(2)


NAME
     send, sendto, sendmsg - send a message from a socket

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

     cc = send(s, msg, len, flags)
     int cc, s;
     char *msg;
     int len, flags;

     cc = sendto(s, msg, len, flags, to, tolen)
     int cc, s;
     char *msg;
     int len, flags;
     struct sockaddr *to;
     int tolen;

     cc = sendmsg(s, msg, flags)
     int cc, s;
     struct msghdr msg[];
     int flags;

DESCRIPTION
     Send, sendto, and sendmsg are used to transmit a message to
     another socket.  Send may be used only when the socket is in
     a connected state, while sendto and sendmsg may be used at
     any time.

     The address of the target is given by to with tolen specify-
     ing its size.  The length of the message is given by len.
     If the message is too long to pass atomically through the
     underlying protocol, then the error EMSGSIZE is returned,
     and the message is not transmitted.

     No indication of failure to deliver is implicit in a send.
     Return values of -1 indicate some locally detected errors.

     If no messages space is available at the socket to hold the
     message to be transmitted, then send normally blocks, unless
     the socket has been placed in non-blocking I/O mode.  The
     select(2) call may be used to determine when it is possible
     to send more data.

     The flags parameter may include one or more of the follow-
     ing:

	  #define  MSG_OOB	   0x1	  /* process out-of-band data */
	  #define  MSG_DONTROUTE   0x4	  /* bypass routing, use direct interface */
     The flag MSG_OOB is used to send "out-of-band" data on sock-
     ets that support this notion (e.g. SOCK_STREAM); the


Printed 11/26/99	  May 14, 1986				1


SEND(2)             UNIX Programmer's Manual		  SEND(2)


     underlying protocol must also support "out-of-band" data.
     MSG_DONTROUTE is usually used only by diagnostic or routing
     programs.

     See recv(2) for a description of the msghdr structure.

RETURN VALUE
     The call returns the number of characters sent, or -1 if an
     error occurred.

ERRORS
     [EBADF]		 An invalid descriptor was specified.

     [ENOTSOCK]          The argument s is not a socket.

     [EFAULT]		 An invalid user space address was speci-
			 fied for a parameter.

     [EMSGSIZE]          The socket requires that message be sent
			 atomically, and the size of the message
			 to be sent made this impossible.

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

     [ENOBUFS]		 The system was unable to allocate an
			 internal buffer.  The operation may
			 succeed when buffers become available.

     [ENOBUFS]		 The output queue for a network interface
			 was full.  This generally indicates that
			 the interface has stopped sending, but
			 may be caused by transient congestion.

SEE ALSO
     fcntl(2), recv(2), select(2), getsockopt(2), socket(2),
     write(2)


Printed 11/26/99	  May 14, 1986				2