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+= nng_sendmsg(3)
+//
+// 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
+
+nng_sendmsg - send message
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nng/nng.h>
+
+int nng_sendmsg(nng_socket s, nng_msg *msg, int flags);
+----
+
+== DESCRIPTION
+
+The `nng_sendmsg()` sends message _msg_ using the socket _s_. 
+
+If the function returns zero, indicating it has accepted the message for
+delivery, then the _msg_ is "`owned`" by the socket _s_, and the caller
+must not make any further use of it.
+The socket will free the message when it is finished.
+
+If the function returns non-zero, then it is the caller's responsibility
+to dispose of the _msg_, which may include freeing it, sending it to
+another socket, or simply trying again later.
+
+TIP: Using this function gives access to the message structure, and may
+offer more functionality than the simpler <<nng_send.3#,`nng_send()`>> function.
+
+NOTE: The semantics of what sending a message means vary from protocol to
+protocol, so examination of the protocol documentation is encouraged.
+(For example, with a <<nng_pub.7#,_pub_>> socket the data is broadcast, so that
+any peers who have a suitable subscription will be able to receive it using
+<<nng_recv.3#,`nng_recv()`>> or a similar function.)
+Furthermore, some protocols may not support sending (such as
+<<nng_sub.7#,_sub_>>) or may require other conditions.
+(For example, <<nng_rep.7#,_rep_>> sockets cannot normally send data, which
+are responses to requests, until they have first received a request.)
+
+The _flags_ may contain the following value:
+
+`NNG_FLAG_NONBLOCK`::
+    The function returns immediately, regardless of whether
+    the socket is able to accept the data or not.
+    If the socket is unable to accept the data (such as if backpressure exists
+    because the peers are consuming messages too slowly, or no peer is present),
+    then the function will return with `NNG_EAGAIN`.
+    If this flag is not specified, then the function will block if such a
+    condition exists.
+
+
+NOTE: Regardless of the presence or absence of `NNG_FLAG_NONBLOCK`, there may
+be queues between the sender and the receiver.
+Furthermore, there is no guarantee that the message has actually been delivered.
+Finally, with some protocols, the semantic is implictly `NNG_FLAG_NONBLOCK`,
+such as with <<nng_pub.7#,_pub_>> sockets, which are best-effort delivery only.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_EAGAIN`:: The socket _s_ cannot accept data for sending.
+`NNG_ECLOSED`:: The socket _s_ is not open.
+`NNG_EINVAL`:: An invalid set of _flags_ was specified.
+`NNG_EMSGSIZE`:: The value of _size_ is too large.
+`NNG_ENOMEM`:: Insufficient memory is available.
+`NNG_ENOTSUP`:: The protocol for socket _s_ does not support sending.
+`NNG_ESTATE`:: The socket _s_ cannot send data in this state.
+
+== SEE ALSO
+
+<<nng_msg_alloc.3#,nng_msg_alloc(3)>>,
+<<nng_recvmsg.3#,nng_recvmsg(3)>>,
+<<nng_send.3#,nng_send(3)>>,
+<<nng_strerror.3#,nng_strerror(3)>>,
+<<nng_msg.5#,nng_msg(5)>>,
+<<nng_socket.5#,nng_socket(5)>>,
+<<nng.7#,nng(7)>>