= nng_listener_set(3)
//
// Copyright 2020 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_set - set listener option

== SYNOPSIS

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

int nng_listener_set(nng_listener l, const char *opt, const void *val, 
    size_t valsz);

int nng_listener_set_bool(nng_listener l, const char *opt, bool bval);

int nng_listener_set_int(nng_listener l, const char *opt, int ival);

int nng_listener_set_ms(nng_listener l, const char *opt, nng_duration dur);

int nng_listener_set_ptr(nng_listener l, const char *opt, void *ptr);

int nng_listener_set_size(nng_listener l, const char *opt, size_t z);

int nng_listener_set_string(nng_listener l, const char *opt, const char *str);

int nng_listener_set_uint64(nng_listener l, const char *opt, uint64_t u64);

----

== DESCRIPTION

(((options, listener)))
The `nng_listener_set()` functions are used to configure options for
the xref:nng_listener.5.adoc[listener] _l_.
The actual options that may be configured 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.

NOTE: Once a listener has started, it is generally not possible to change
its configuration.

=== Forms

In all of these forms, the option _opt_ is configured on the listener _l_.

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.

TIP: It may be easier to use one of the typed forms of this function.

`nng_listener_set()`::
This function is untyped, and can be used to configure any arbitrary data.
The _val_ pointer addresses the data to copy, and _valsz_ is the
size of the objected located at _val_.

`nng_listener_set_bool()`::
This function is for options which take a Boolean (`bool`).
The _bval_ is passed to the option.

`nng_listener_set_int()`::
This function is for options which take an integer (`int`).
The _ival_ is passed to the option.

`nng_listener_set_ms()`::
This function is used to configure time durations (such as timeouts) using
type xref:nng_duration.5.adoc[`nng_duration`].
The duration _dur_ is an integer number of milliseconds.

`nng_listener_set_ptr()`::
This function is used to pass a pointer, _ptr_, to structured data.
The data referenced by _ptr_ is generally managed by other functions.
For example, TLS configuration objects created with
(xref:nng_tls_config_alloc.3tls.adoc[`nng_tls_config_alloc()`])
can be passed this way.

NOTE: This form is somewhat special in that the object is generally
not copied, but instead the *pointer* to the object is copied.

`nng_listener_set_size()`::
This function is used to configure a size, _z_, typically for buffer sizes,
message maximum sizes, and similar options.

`nng_listener_set_string()`::
This function is used to pass configure a string, _str_.
Strings passed this way must be legal UTF-8 or ASCII strings, terminated
with a `NUL` (`\0`) byte.
(Other constraints may apply as well, see the documentation for each option
for details.)

`nng_listener_set_uint64()`::
This function is used to configure a 64-bit unsigned value, _u64_.
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`:: The value being passed is invalid.
`NNG_ENOTSUP`:: The option _opt_ is not supported.
`NNG_EREADONLY`:: The option _opt_ is read-only.
`NNG_ESTATE`:: The listener _l_ is already started.

== 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_get.3.adoc[nng_listener_get(3)]
xref:nng_socket_set.3.adoc[nng_socket_set(3)],
xref:nng_strerror.3.adoc[nng_strerror(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.7.adoc[nng(7)]