= nn_send(3compat)
//
// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// This document is supplied under the terms of the MIT License, a
// copy of which should be located in the distribution where this
// file was obtained (LICENSE.txt).  A copy of the license may also be
// found online at https://opensource.org/licenses/MIT.
//

== NAME

nn_send - send data (compatible API)

== SYNOPSIS

[source, c]
----
#include <nanomsg/nn.h>

int nn_send(int sock, const void *data, size_t size, int flags)
----

== DESCRIPTION

The `nn_send()` function creates a message containing _data_ (of size _size_),
and sends using the socket _sock_.

NOTE: This function is provided for API
xref:nng_compat.3compat.adoc[compatibility] with legacy _libnanomsg_.
Consider using the relevant xref:libnng.3.adoc[modern API] instead.

If _size_ has the special value `NN_MSG`, then a zero-copy operation
is performed.
In this case, _data_ points not to the message content itself, but instead
is a pointer to the pointer, an extra level of pointer indirection.
The message must have been previously allocated by
xref:nn_allocmsg.3compat.adoc[`nn_allocmsg()`] or
xref:nn_recvmsg.3compat.adoc[`nn_recvmsg()`]`, using the same `NN_MSG` size.
In this case, the "`ownership`" of the message shall remain with
the caller, unless the function returns 0, indicating that the
function has taken responsibility for delivering or disposing of the
message.

The _flags_ field may contain the special flag `NN_DONTWAIT`.
In this case, if the socket is unable to accept more data for sending,
the operation shall not block, but instead will fail with the error `EAGAIN`.

NOTE: The send operation is performed asynchronously, and may not have
completed before this function returns control to the caller.

== RETURN VALUES

This function returns the number of bytes sent on success, and -1 on error.

== ERRORS

[horizontal]
`EAGAIN`:: The operation would block.
`EBADF`:: The socket _sock_ is not open.
`EFSM`:: The socket cannot send in this state.
`ENOTSUP`:: This protocol cannot send.
`ETIMEDOUT`:: Operation timed out.

== SEE ALSO

[.text-left]
xref:nn_errno.3compat.adoc[nn_errno(3compat)],
xref:nn_recv.3compat.adoc[nn_recv(3compat)],
xref:nn_sendmsg.3compat.adoc[nn_sendmsg(3compat)],
xref:nn_socket.3compat.adoc[nn_socket(3compat)],
xref:nng_compat.3compat.adoc[nn_compat(3compat)],
xref:nng.7.adoc[nng(7)]