= nng_socket(5)
//
// Copyright 2018 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_socket - socket handle

== SYNOPSIS

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

typedef struct nng_socket_s nng_socket;
----

== DESCRIPTION

An `nng_socket`(((socket))) is a handle to an underlying socket object.
All communication between the application and remote Scalability Protocol
peers is done through sockets.
A given socket can have multiple dialers (xref:nng_dialer.5.adoc[`nng_dialer`])
and/or listeners (xref:nng_listener.5.adoc[`nng_listener`]), and multiple
pipes (xref:nng_pipe.5.adoc[`nng_pipe`]), and
may be connected to multiple transports at the same time.
However, a given socket will have exactly one protocol associated with it,
and is responsible for any state machines or other protocol-specific logic.

IMPORTANT: The `nng_socket` 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.

Each `nng_socket` is created by a protocol-specific constructor, such as
xref:nng_rep_open.3.adoc[`nng_rep_open()`].
When the socket is no longer needed, it can be closed with
xref:nng_close.3.adoc[`nng_close()`].

[[NNG_SOCKET_INITIALIZER]]
=== Initialization

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

For example:

[source, c]
----
nng_socket s = NNG_SOCKET_INITIALIZER;
----

== SEE ALSO

[.text-left]
xref:libnng.3.adoc[libnng(3)],
xref:nng_close.3.adoc[nng_close(3)],
xref:nng_getopt.3.adoc[nng_getopt(3)],
xref:nng_setopt.3.adoc[nng_setopt(3)],
xref:nng_socket_id.3.adoc[nng_socket_id(3)],
xref:nng_dialer.5.adoc[nng_dialer(5)],
xref:nng_listener.5.adoc[nng_listener(5)],
xref:nng_options.5.adoc[nng_options(5)],
xref:nng.7.adoc[nng(7)]