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|
= nng_rep(7)
//
// 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_rep - reply protocol
SYNOPSIS
--------
[source,c]
----------
#include <nng/protocol/reqrep0/rep.h>
int nng_rep0_open(nng_socket *s);
----------
DESCRIPTION
-----------
The _nng_rep_ protocol is one half of a request/reply pattern.
In this pattern, a requester sends a message to one replier, who
is expected to reply. The request is resent if no reply arrives,
until a reply is received or the request times out.
TIP: This protocol is useful in setting up RPC-like services. It
is also "reliable", in that a the requester will keep retrying until
a reply is received.
The _nng_rep_ protocol is the replier side, and the
<<nng_req#,nng_req(7)>> protocol is the requester side.
Socket Operations
~~~~~~~~~~~~~~~~~
The `nng_rep0_open()` call creates a requester socket. This socket
may be used to receive messages (requests), and then to send replies. Generally
a reply can only be sent after receiving a request. (Attempts to receive
a message will result in `NNG_ESTATE` if there is no outstanding request.)
Attempts to send on a socket with no outstanding requests will result
in `NNG_ESTATE`.
Raw mode sockets (set with `NNG_OPT_RAW`) ignore all these restrictions.
Protocol Versions
~~~~~~~~~~~~~~~~~
Only version 0 of this protocol is supported. (At the time of writing,
no other versions of this protocol have been defined.)
Protocol Options
~~~~~~~~~~~~~~~~
The following protocol-specific options are available.
`NNG_OPT_MAXTTL`::
Maximum time-to-live. This option is an integer value
between 0 and 255,
inclusive, and is the maximum number of "hops" that a message may
pass through until it is discarded. The default value is 8. A value
of 0 may be used to disable the loop protection, allowing an infinite
number of hops.
Protocol Headers
~~~~~~~~~~~~~~~~
The _nng_rep_ protocol uses a _backtrace_ in the header. This is
more fully documented in the <<nng_req#,nng_req(7)>> manual.
SEE ALSO
--------
<<nng#,nng(7)>>,
<<nng_req#,nng_req(7)>>
|
