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+# nng_sendmsg
+
+## NAME
+
+nng_sendmsg --- send message
+
+## SYNOPSIS
+
+```
+#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 xref:nng_send.3.adoc[`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 xref:nng_pub.7.adoc[_pub_] socket the data is broadcast, so that
+any peers who have a suitable subscription will be able to receive it using
+xref:nng_recv.3.adoc[`nng_recv()`] or a similar function.)
+Furthermore, some protocols may not support sending (such as
+xref:nng_sub.7.adoc[_sub_]) or may require other conditions.
+(For example, xref:nng_rep.7.adoc[_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 implicitly `NNG_FLAG_NONBLOCK`,
+such as with xref:nng_pub.7.adoc[_pub_] sockets, which are best-effort delivery only.
+
+## RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+## ERRORS
+
+* `NNG_EAGAIN`: The operation would block, but `NNG_FLAG_NONBLOCK` was specified.
+* `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.
+* `NNG_ETIMEDOUT`: The operation timed out.
+
+## SEE ALSO
+
+[nng_msg_alloc][nng_msg_alloc],
+[nng_recvmsg][nng_recvmsg],
+[nng_send][nng_send],
+[nng_strerror][nng_strerror],
+[nng_msg][nng_msg],
+[nng_socket][nng_socket],
+[nng][nng]
+
+{{#include ../refs.md}}