= nng_ctx_open(3)
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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_ctx_open - create context
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== SYNOPSIS
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[source,c]
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----
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#include <nng/nng.h>
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int nng_ctx_open(nng_ctx *ctxp, nng_socket s);
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----
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== DESCRIPTION
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The `nng_ctx_open()` function creates a separate ((context)) to be used with
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the socket _s_,
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and returns it at the location pointed by _ctxp_.
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NOTE: Not every protocol supports creation of separate contexts.
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Contexts allow the independent and concurrent use of stateful operations
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using the same socket.
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For example, two different contexts created on a xref:nng_rep.7.adoc[_rep_]
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socket can each receive requests, and send replies to them, without any
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regard to or interference with each other.
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(((raw mode)))
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TIP: Using contexts is an excellent way to write simpler concurrent
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applications, while retaining the benefits of the protocol-specific
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advanced processing, avoiding the need to bypass that with
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xref:nng.7.adoc#raw_mode[raw mode] sockets.
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NOTE: Use of contexts with xref:nng.7.adoc#raw_mode[raw mode] sockets is
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nonsensical, and not supported.
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== RETURN VALUES
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This function returns 0 on success, and non-zero otherwise.
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== ERRORS
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[horizontal]
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`NNG_ENOMEM`:: Insufficient memory is available.
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`NNG_ENOTSUP`:: The protocol does not support separate contexts, or the socket was opened in raw mode.
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== SEE ALSO
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[.text-left]
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xref:nng_ctx_close.3.adoc[nng_ctx_close(3)],
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xref:nng_ctx_getopt.3.adoc[nng_ctx_getopt(3)],
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xref:nng_ctx_recv.3.adoc[nng_ctx_recv(3)],
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xref:nng_ctx_send.3.adoc[nng_ctx_send(3)],
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xref:nng_ctx_setopt.3.adoc[nng_ctx_setopt(3)],
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xref:nng_strerror.3.adoc[nng_strerror(3)],
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xref:nng_ctx.5.adoc[nng_ctx(5)],
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xref:nng_socket.5.adoc[nng_socket(5)],
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xref:nng_rep.7.adoc[nng_rep(7)],
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xref:nng_req.7.adoc[nng_req(7)],
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xref:nng.7.adoc[nng(7)]
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