NAME

       xs_send - send a message part on a socket

SYNOPSIS

       int xs_send (void *socket, void *buf, size_t len, int flags);

DESCRIPTION

       The xs_send() function shall queue a message created from the buffer referenced by the buf
       and len arguments. The flags argument is a combination of the flags defined below:

       XS_DONTWAIT
           Specifies that the operation should be performed in non-blocking mode. If the message
           cannot be queued on the socket, the xs_send() function shall fail with errno set to
           EAGAIN.

       XS_SNDMORE
           Specifies that the message being sent is a multi-part message, and that further
           message parts are to follow. Refer to the section regarding multi-part messages below
           for a detailed description.

           Note
           A successful invocation of xs_send() does not indicate that the message has been
           transmitted to the network, only that it has been queued on the socket and Crossroads
           have assumed responsibility for the message.

   Multi-part messages
       A Crossroads message is composed of 1 or more message parts. Crossroads ensures atomic
       delivery of messages; peers shall receive either all message parts of a message or none at
       all. The total number of message parts is unlimited except by available memory.

       An application that sends multipart messages must use the XS_SNDMORE flag when sending
       each message part except the final one.

RETURN VALUE

       The xs_send() function shall return number of bytes in the message if successful.
       Otherwise it shall return -1 and set errno to one of the values defined below.

ERRORS

       EAGAIN
           Non-blocking mode was requested and the message cannot be sent at the moment.

       ENOTSUP
           The xs_send() operation is not supported by this socket type.

       EFSM
           The xs_send() operation cannot be performed on this socket at the moment due to the
           socket not being in the appropriate state. This error may occur with socket types that
           switch between several states, such as XS_REP. See the messaging patterns section of
           xs_socket(3) for more information.

       ETERM
           The context associated with the specified socket was terminated.

       ENOTSOCK
           The provided socket was invalid.

       EINTR
           The operation was interrupted by delivery of a signal before the message was sent.

EXAMPLE

       Sending a multi-part message.

           /* Send a multi-part message consisting of three parts to socket */
           rc = xs_send (socket, "ABC", 3, XS_SNDMORE);
           assert (rc == 3);
           rc = xs_send (socket, "DEFGH", 5, XS_SNDMORE);
           assert (rc == 5);
           /* Final part; no more parts to follow */
           rc = xs_send (socket, "JK", 2, 0);
           assert (rc == 2);

SEE ALSO

       Applications that wish to use zero-copy messaging must use xs_sendmsg(3) instead of
       xs_send().

       xs_recv(3) xs_socket(7) xs(7)

AUTHORS

       This man page was written by Martin Sustrik <sustrik@250bpm.com[1]>, Martin Lucina
       <martin@lucina.net[2]> and Pieter Hintjens <ph@imatix.com[3]>.

NOTES

        1. sustrik@250bpm.com
           mailto:sustrik@250bpm.com

        2. martin@lucina.net
           mailto:martin@lucina.net

        3. ph@imatix.com
           mailto:ph@imatix.com