linux man page for send

SEND(P) 						     POSIX Programmer's Manual							   SEND(P)

NAME
       send - send a message on a socket

SYNOPSIS
       #include <sys/socket.h>

       ssize_t send(int socket, const void *buffer, size_t length, int flags);

DESCRIPTION
       The  send()  function shall initiate transmission of a message from the specified socket to its peer. The send() function shall send a mes-
       sage only when the socket is connected (including when the peer of a connectionless socket has been set via connect()).

       The send() function takes the following arguments:

       socket Specifies the socket file descriptor.

       buffer Points to the buffer containing the message to send.

       length Specifies the length of the message in bytes.

       flags  Specifies the type of message transmission. Values of this argument are formed by logically OR'ing zero or  more	of  the  following
	      flags:

       MSG_EOR
	      Terminates a record (if supported by the protocol).

       MSG_OOB
	      Sends  out-of-band  data on sockets that support out-of-band communications.  The significance and semantics of out-of-band data are
	      protocol-specific.

       The length of the message to be sent is specified by the length argument. If the message is too long to pass through the underlying  proto-
       col, send() shall fail and no data shall be transmitted.

       Successful  completion of a call to send() does not guarantee delivery of the message. A return value of -1 indicates only locally-detected
       errors.

       If space is not available at the sending socket to hold the message to be transmitted, and the socket file descriptor does not have  O_NON-
       BLOCK  set,  send() shall block until space is available.  If space is not available at the sending socket to hold the message to be trans-
       mitted, and the socket file descriptor does have O_NONBLOCK set, send() shall fail. The select() and poll() functions can be used to deter-
       mine when it is possible to send more data.

       The socket in use may require the process to have appropriate privileges to use the send() function.

RETURN VALUE
       Upon  successful  completion,  send()  shall return the number of bytes sent. Otherwise, -1 shall be returned and errno set to indicate the
       error.

ERRORS
       The send() function shall fail if:

       EAGAIN or EWOULDBLOCK

	      The socket's file descriptor is marked O_NONBLOCK and the requested operation would block.

       EBADF  The socket argument is not a valid file descriptor.

       ECONNRESET
	      A connection was forcibly closed by a peer.

       EDESTADDRREQ

	      The socket is not connection-mode and no peer address is set.

       EINTR  A signal interrupted send() before any data was transmitted.

       EMSGSIZE
	      The message is too large to be sent all at once, as the socket requires.

       ENOTCONN
	      The socket is not connected or otherwise has not had the peer pre-specified.

       ENOTSOCK
	      The socket argument does not refer to a socket.

       EOPNOTSUPP
	      The socket argument is associated with a socket that does not support one or more of the values set in flags.

       EPIPE  The socket is shut down for writing, or the socket is connection-mode and is no longer connected. In the latter  case,  and  if  the
	      socket is of type SOCK_STREAM, the SIGPIPE signal is generated to the calling thread.

       The send() function may fail if:

       EACCES The calling process does not have the appropriate privileges.

       EIO    An I/O error occurred while reading from or writing to the file system.

       ENETDOWN
	      The local network interface used to reach the destination is down.

       ENETUNREACH

	      No route to the network is present.

       ENOBUFS
	      Insufficient resources were available in the system to perform the operation.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       The send() function is equivalent to sendto() with a null pointer dest_len argument, and to write() if no flags are used.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       connect()  ,  getsockopt()  ,  poll()  ,  recv()  ,  recvfrom() , recvmsg() , select() , sendmsg() , sendto() , setsockopt() , shutdown() ,
       socket() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/socket.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								   SEND(P)