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>

typedef struct nng_listener_s nng_listener;


An nng_listener is a handle to a “listener” object, which is responsible for creating nng_pipe objects by accepting incoming connections. A given listener object may create many pipes at the same time, much like an HTTP server can have many connections to multiple clients simultaneously.

Listener objects are created by the nng_listener_create() or nng_listen() functions, and are always “owned” by a single nng_socket.

The nng_listener structure is always passed by value (both for input parameters and return values), and should be treated opaquely. Passing structures this way gives the compiler a chance to perform accurate type checks in functions passing values of this type.
A given nng_socket may have multiple listener objects, multiple dialer objects, or even some of both.
The client/server relationship described by dialer/listener is completely orthogonal to any similar relationship in the protocols. For example, a rep socket may use a dialer to connect to a listener on an req socket. This orthogonality can lead to innovative solutions to otherwise challenging communications problems.

Listener objects may be destroyed by the nng_listener_close() function. They are also closed when their “owning” socket is closed.


A listener may be initialized using the macro NNG_LISTENER_INITIALIZER before it is opened, to prevent confusion with valid open listener.