This documentation is for version v1.3.0 of NNG, but the latest released version is v1.8.0. see the documentation for v1.8.0 for the most up-to-date information.


#include <nng/nng.h>

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

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

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

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

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

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

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

int nng_listener_setopt_uint64(nng_listener l, const char *opt, uint64_t u64);


These functions are deprecated. Please see nng_listener_set.

The nng_listener_setopt() functions are used to configure options for the listener l. The actual options that may be configured in this way vary, and many are documented in nng_options(5).

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

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


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.

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

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.


This function is for options which take a Boolean (bool). The bval is passed to the option.


This function is for options which take an integer (int). The ival is passed to the option.


This function is used to configure time durations (such as timeouts) using type nng_duration. The duration dur is an integer number of milliseconds.


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 (nng_tls_config_alloc()) can be passed this way.

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

This function is used to configure a size, z, typically for buffer sizes, message maximum sizes, and similar options.


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.)


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.


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



Incorrect type for option.


Parameter l does not refer to an open listener.


The value being passed is invalid.


The option opt is not supported.


The option opt is read-only.


The listener l is already started.