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NN_SENDMSG(3)                   nanomsg manual                   NN_SENDMSG(3)

NAME
       nn_sendmsg - fine-grained alternative to nn_send

SYNOPSIS
       #include <nanomsg/nn.h>

       int nn_sendmsg (int s, const struct nn_msghdr *msghdr, int flags);

DESCRIPTION
       Sends data specified by msghdr parameter to socket s along with any
       additional control data. msghdr structure should be nullified before
       being used.

       Structure nn_msghdr contains at least following members:

           struct nn_iovec *msg_iov;
           int msg_iovlen;
           void *msg_control;
           size_t msg_controllen;

       msg_iov points to a scatter array of buffers to send. msg_iovlen
       specifies the size of the array.

       msg_control points to the buffer containing control information to be
       associated with the message being sent. msg_controllen specifies the
       length of the buffer. If there's no control information to send,
       msg_control should be set to NULL. For detailed discussion of how to
       set control data check nn_cmsg(3) man page.

       Structure nn_iovec defines one element in the scatter array (i.e. a
       buffer to send to the socket) and contains following members:

           void *iov_base;
           size_t iov_len;

       Alternatively, to send a buffer allocated by nn_allocmsg(3) function
       set iov_base to point to the pointer to the buffer and iov_len to
       NN_MSG constant. In this case a successful call to nn_sendmsg will
       deallocate the buffer. Trying to deallocate it afterwards will result
       in undefined behaviour. Also, scatter array in nn_msghdr structure can
       contain only one element in this case.

       To which of the peers will the message be sent to is determined by the
       particular socket type.

       The flags argument is a combination of the flags defined below:

       NN_DONTWAIT
           Specifies that the operation should be performed in non-blocking
           mode. If the message cannot be sent straight away, the function
           will fail with errno set to EAGAIN.

RETURN VALUE
       If the function succeeds number of bytes in the message is returned.
       Otherwise, -1 is returned and errno is set to to one of the values
       defined below.

ERRORS
       EINVAL
           Either msghdr is NULL, there are multiple scatter buffers but
           length is set to NN_MSG for one of them, or the sum of iov_len
           values for the scatter buffers overflows size_t. These are early
           checks and no pre-allocated message is freed in this case.

       EMSGSIZE
           msghdr->msg_iovlen is negative. This is an early check and no
           pre-allocated message is freed in this case.

       EFAULT
           The supplied pointer for the pre-allocated message buffer or the
           scatter buffer is NULL, or the length for the scatter buffer is 0.

       EBADF
           The provided socket is invalid.

       ENOTSUP
           The operation is not supported by this socket type.

       EFSM
           The operation cannot be performed on this socket at the moment
           because socket is not in the appropriate state. This error may
           occur with socket types that switch between several states.

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

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

       ETIMEDOUT
           Individual socket types may define their own specific timeouts. If
           such timeout is hit this error will be returned.

       ETERM
           The library is terminating.

EXAMPLE
       Usage of multiple scatter buffers:

           struct nn_msghdr hdr;
           struct nn_iovec iov [2];

           iov [0].iov_base = "Hello";
           iov [0].iov_len = 5;
           iov [1].iov_base = "World";
           iov [1].iov_len = 5;
           memset (&hdr, 0, sizeof (hdr));
           hdr.msg_iov = iov;
           hdr.msg_iovlen = 2;
           nn_sendmsg (s, &hdr, 0);

       Usage of a single message:

           void *msg;
           struct nn_msghdr hdr;
           struct nn_iovec iov;

           msg = nn_allocmsg(12, 0);
           strcpy(msg, "Hello World");
           iov.iov_base = &msg;
           iov.iov_len = NN_MSG;
           memset (&hdr, 0, sizeof (hdr));
           hdr.msg_iov = &iov;
           hdr.msg_iovlen = 1;
           nn_sendmsg (s, &hdr, 0);

SEE ALSO
       nn_send(3) nn_recvmsg(3) nn_allocmsg(3) nn_freemsg(3) nn_cmsg(3)
       nanomsg(7)

AUTHORS
       Martin Sustrik <sustrik@250bpm.com[1]>

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

nanomsg Unknown                   12/23/2015                     NN_SENDMSG(3)