= nng_listener_get(3)
//
// Copyright 2024 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_listener_get - get listener option

== SYNOPSIS

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

int nng_listener_get_bool(nng_listener l, const char *opt, bool *bvalp);

int nng_listener_get_int(nng_listener l, const char *opt, int *ivalp);

int nng_listener_get_ms(nng_listener l, const char *opt, nng_duration *durp);

int nng_listener_get_size(nng_listener l, const char *opt, size_t *zp);

int nng_listener_get_string(nng_listener l, const char *opt, const char **strp);

int nng_listener_get_uint64(nng_listener l, const char *opt, uint64_t *u64p);

----

== DESCRIPTION

(((options, listener)))
The `nng_listener_get` functions are used to retrieve option values for
the xref:nng_listener.5.adoc[listener] _l_.
The actual options that may be retrieved in this way
vary, and many are documented in xref:nng_options.5.adoc[nng_options(5)].

Additionally some transport-specific options are documented with the transports themselves.

=== Forms

In all of these forms, the option _opt_ is retrieved from the listener _l_.
The forms vary based on the type of the option they take.

The details of the type, size, and semantics of the option will depend
on the actual option, and will be documented with the option itself.

`nng_listener_get_bool()`::
This function is for options which take a Boolean (`bool`).
The value will be stored at _bvalp_.

`nng_listener_get_int()`::
This function is for options which take an integer (`int`).
The value will be stored at _ivalp_.

`nng_listener_get_ms()`::
This function is used to retrieve time xref:nng_duration.5.adoc[durations]
(such as timeouts), stored in _durp_ as a number of milliseconds.

`nng_listener_get_size()`::
This function is used to retrieve a size into the pointer _zp_,
typically for buffer sizes, message maximum sizes, and similar options.

`nng_listener_get_string()`::
This function is used to retrieve a string into _strp_.

`nng_listener_get_uint64()`::
This function is used to retrieve a 64-bit unsigned value into the value
referenced by _u64p_.
This is typically used for options related to identifiers, network
numbers, and similar.

== RETURN VALUES

These functions return 0 on success, and non-zero otherwise.

== ERRORS

[horizontal]
`NNG_EBADTYPE`:: Incorrect type for option.
`NNG_ECLOSED`:: Parameter _l_ does not refer to an open listener.
`NNG_EINVAL`:: Size of destination _val_ too small for object.
`NNG_ENOMEM`:: Insufficient memory exists.
`NNG_ENOTSUP`:: The option _opt_ is not supported.
`NNG_EWRITEONLY`:: The option _opt_ is write-only.

== SEE ALSO

[.text-left]
xref:nng_listen.3.adoc[nng_listen(3)],
xref:nng_listener_create.3.adoc[nng_listener_create(3)]
xref:nng_listener_set.3.adoc[nng_listener_set(3)]
xref:nng_socket_get.3.adoc[nng_socket_get(3)],
xref:nng_strdup.3.adoc[nng_strdup(3)],
xref:nng_strerror.3.adoc[nng_strerror(3)],
xref:nng_strfree.3.adoc[nng_strfree(3)],
xref:nng_duration.5.adoc[nng_duration(5)],
xref:nng_listener.5.adoc[nng_listener(5)],
xref:nng_options.5.adoc[nng_options(5)],
xref:nng_sockaddr.5.adoc[nng_sockaddr(5)],
xref:nng.7.adoc[nng(7)]
