# nng_listener(5) Manual Page

## NAME

nng_listener - listener

## SYNOPSIS

    #include <nng/nng.h>

    typedef struct nng_listener_s nng_listener;

## DESCRIPTION

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 associated with 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 associated socket is closed.

### Initialization

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

## SEE ALSO

nng_listen(3), nng_listener_close(3), nng_listener_create(3), nng_listener_getopt(3), nng_listener_id(3), nng_listener_setopt(3), nng_listener_start(3), nng_dialer(5), nng_pipe(5), nng_socket(5), nng(7)