= nng_msg_header(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_msg_header - return message header

== SYNOPSIS

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

void *nng_msg_header(nng_msg *msg);
----

== DESCRIPTION

The `nng_msg_header()` function returns a pointer to the start of the header
content of the message _msg_.

NOTE: The message header contains protocol-specific header content.  Most
applications should not need to access this content, but it is available
for raw mode sockets (set with the
<<nng_options.5#NNG_OPT_RAW,`NNG_OPT_RAW`>> option.)

NOTE: The value returned by this is invalidated by a call to any of the
functions that modify the message or the header content.

== RETURN VALUES

Pointer to start of message header.

== ERRORS

None.

== SEE ALSO

<<nng_msg_alloc.3#,nng_msg_alloc(3)>>,
<<nng_msg_body.3#,nng_msg_body(3)>>,
<<nng_msg_free.3#,nng_msg_free(3)>>,
<<nng_msg_header_append.3#,nng_msg_header_append(3)>>,
<<nng_msg_header_chop.3#,nng_msg_header_chop(3)>>,
<<nng_msg_header_insert.3#,nng_msg_header_insert(3)>>
<<nng_msg_header_len.3#,nng_msg_header_len(3)>>,
<<nng_msg_header_trim.3#,nng_msg_header_trim(3)>>,
<<nng_msg.5#,nng_msg(5)>>,
<<nng.7#,nng(7)>>