96 lines
3.5 KiB
Text
96 lines
3.5 KiB
Text
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= nng_dial(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_dial - create and start dialer
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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_dial(nng_socket s, const char *url, nng_dialer *dp, int flags);
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----
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== DESCRIPTION
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The `nng_dial()` function creates a newly initialized
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xref:nng_dialer.5.adoc[`nng_dialer`] object,
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associated with socket _s_, and configured to dial the
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address specified by _url_, and starts it.
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If the value of _dp_ is not `NULL`, then
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the newly created dialer is stored at the address indicated by _dp_.
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Dialers initiate a remote connection to a listener.
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Upon a successful
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connection being established, they create a xref:nng_pipe.5.adoc[pipe],
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add it to the socket, and then wait for that pipe to be closed.
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When the pipe is closed, the dialer attempts to re-establish the connection.
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Dialers will also periodically retry a connection automatically if an attempt
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to connect asynchronously fails.
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TIP: While it is convenient to think of dialers as clients, the relationship
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between the listener or dialer is orthogonal to any server or client status
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that might be associated with a given protocol.
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For example, a xref:nng_req.7.adoc[_req_]
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socket might have associated dialers, but might also have associated listeners.
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It may even have some of each at the same time!
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Normally, the first attempt to connect to the address indicated by _url_ is done
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synchronously, including any necessary name resolution.
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As a result, a failure, such as if the connection is refused, will be returned
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immediately, and no further action will be taken.
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However, if the special value `NNG_FLAG_NONBLOCK` is
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supplied in _flags_, then the connection attempt is made asynchronously.
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Furthermore, if the connection was closed for a synchronously dialed
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connection, the dialer will still attempt to redial asynchronously.
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TIP: While `NNG_FLAG_NONBLOCK` can help an application be more resilient,
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it also generally makes diagnosing failures somewhat more difficult.
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Because the dialer is started immediately, it is generally not possible
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to apply extra configuration; if that is needed applications should consider
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using xref:nng_dialer_create.3.adoc[`nng_dialer_create()`] and
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xref:nng_dialer_start.3.adoc[`nng_dialer_start()`] instead.
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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_EADDRINVAL`:: An invalid _url_ was specified.
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`NNG_ECLOSED`:: The socket _s_ is not open.
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`NNG_ECONNREFUSED`:: The remote peer refused the connection.
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`NNG_ECONNRESET`:: The remote peer reset the connection.
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`NNG_EINVAL`:: An invalid set of _flags_ or an invalid _url_ was specified.
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`NNG_ENOMEM`:: Insufficient memory is available.
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`NNG_EPEERAUTH`:: Authentication or authorization failure.
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`NNG_EPROTO`:: A protocol error occurred.
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`NNG_EUNREACHABLE`:: The remote address is not reachable.
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== SEE ALSO
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[.text-left]
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xref:nng_dialer_close.3.adoc[nng_dialer_close(3)],
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xref:nng_dialer_create.3.adoc[nng_dialer_create(3)]
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xref:nng_dialer_start.3.adoc[nng_dialer_start(3)],
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xref:nng_listen.3.adoc[nng_listen(3)],
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xref:nng_strerror.3.adoc[nng_strerror(3)],
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xref:nng_dialer.5.adoc[nng_dialer(5)],
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xref:nng_pipe.5.adoc[nng_pipe(5)],
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xref:nng.7.adoc[nng(7)]
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