= nng_socket_proto_id(3)
//
// Copyright 2024 Staysail Systems, Inc. <info@staysail.tech>
//
// 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_proto_id - obtain the socket protocol id

== SYNOPSIS

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

int nng_socket_proto_id(nng_socket s, uint16_t *id);
int nng_socket_peer_id(nng_socket s, uint16_t *id);
----

== DESCRIPTION

These functions store the 16-bit protocol identifier of either the socket _s_,
or its natural peer, in _id_.

TIP: These functions should be used in place of the `NNG_OPT_PROTO` and `NNG_OPT_PEER`
options in new code.

== RETURN VALUES

These functions return zero on success, or an error if the socket is invalid.

== ERRORS

[horizontal]
`NNG_ECLOSED`:: Parameter _s_ does not refer to an open socket.

== SEE ALSO

[.text-left]
xref:nng_socket.5.adoc[nng_socket(5)],
xref:nng.7.adoc[nng(7)]