87 lines
2.5 KiB
Text
87 lines
2.5 KiB
Text
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= nng_rep(7)
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//
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// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
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// Copyright 2018 Capitar IT Group BV <info@capitar.com>
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//
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// This document is supplied under the terms of the MIT License, a
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// copy of which should be located in the distribution where this
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// file was obtained (LICENSE.txt). A copy of the license may also be
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// found online at https://opensource.org/licenses/MIT.
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//
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== NAME
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nng_rep - reply protocol
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== SYNOPSIS
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[source,c]
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----
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#include <nng/protocol/reqrep0/rep.h>
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----
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== DESCRIPTION
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(((protocol, _rep_)))
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The ((_rep_ protocol)) is one half of a ((request/reply pattern)).
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In this pattern, a requester sends a message to one replier, who
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is expected to reply.
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The request is resent if no reply arrives,
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until a reply is received or the request times out.
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TIP: This protocol is useful in setting up RPC-like services.
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It is also reliable, in that a requester will keep retrying until
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a reply is received.
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The _rep_ protocol is the replier side, and the
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xref:nng_req.7.adoc[_req_] protocol is the requester side.
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=== Socket Operations
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The xref:nng_rep_open.3.adoc[`nng_rep0_open()`] functions create a replier socket.
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This socket may be used to receive messages (requests), and then to send
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replies.
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Generally a reply can only be sent after receiving a request.
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Send operations will result in `NNG_ESTATE` if no corresponding request
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was previously received.
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Likewise, only one receive operation may be pending at a time.
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Any additional concurrent receive operations will result in `NNG_ESTATE`.
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xref:nng.7.adoc#raw_mode[Raw] mode sockets ignore all these restrictions.
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=== Context Operations
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This protocol supports the creation of xref:nng_ctx.5.adoc[contexts] for concurrent
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use cases using xref:nng_ctx_open.3.adoc[`nng_ctx_open()`].
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Each context may have at most one outstanding request, and operates
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independently of the others.
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The restrictions for order of operations with sockets apply equally
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well for contexts, except that each context will be treated as if it were
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a separate socket.
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=== Protocol Versions
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Only version 0 of this protocol is supported.
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(At the time of writing, no other versions of this protocol have been defined.)
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==== Protocol Options
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The _rep_ protocol has no protocol-specific options.
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==== Protocol Headers
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(((backtrace)))
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The _rep_ protocol uses a _backtrace_ in the header.
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This is more fully documented in the xref:nng_req.7.adoc[_req_] manual.
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== SEE ALSO
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[.text-left]
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xref:nng_rep_open.3.adoc[nng_rep_open(3)],
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xref:nng.7.adoc[nng(7)],
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xref:nng_req.7.adoc[nng_req(7)]
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