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+} + +</style> +<h1 id="streams"><a class="header" href="#streams">Streams</a></h1> +<p>NNG provides a common <a name="a001"></a>streams API for working with byte-oriented streams. In NNG, streams are bidirectional +connections for exchanging a stream of bytes.</p> +<p>Some common examples of streams are TCP connections, UNIX domain sockets, Windows named pipes, and WebSockets.</p> +<p>The API documented here is to facilitate applications that wish to work with these at a lower-level than +Scalability Protocols, in a way that is both portable and agnostic about the specific underlying transport mechanism.</p> +<div class="mdbook-alerts mdbook-alerts-tip"> +<p class="mdbook-alerts-title"> + <span class="mdbook-alerts-icon"></span> + tip +</p> +<p>When working with Scalability Protocols directly, it is unlikely that there will be any need for +using these Streams APIs.</p> +</div> +<h2 id="stream-type"><a class="header" href="#stream-type">Stream Type</a></h2> +<pre><code class="language-c">typedef struct nng_stream nng_stream` +</code></pre> +<p>The base <a name="a002"></a><code>nng_stream</code> type represents a bidirectional, byte-oriented, reliable connection.</p> +<div class="mdbook-alerts mdbook-alerts-note"> +<p class="mdbook-alerts-title"> + <span class="mdbook-alerts-icon"></span> + note +</p> +<p>The <code>nng_stream</code> object is used for raw byte stream connections, and +should not be confused with a <a href="/TODO.html">pipe</a> object created on a <a href="/TODO.html">socket</a> using +the [<code>nng_listen</code>], [<code>nng_dial</code>] or related functions.</p> +</div> +<h2 id="sending-and-receiving-data"><a class="header" href="#sending-and-receiving-data">Sending and Receiving Data</a></h2> +<pre><code class="language-c">void nng_stream_send(nng_stream *s, nng_aio *aio); +void nng_stream_recv(nng_stream *s, nng_aio *aio); +</code></pre> +<p>The <a name="a003"></a><code>nng_stream_send</code> function starts sending data asynchronously over the stream <em>s</em>. +The data is sent from the scatter/gather vector located in the <a href="/api/aio.html#asynchronous-io-handle"><code>nng_aio</code></a> <em>aio</em>, +which must have been previously set using <a href="/api/aio.html#scatter-gather-vectors"><code>nng_aio_set_iov</code></a>.</p> +<p>The <a name="a004"></a><code>nng_stream_recv</code> function starts receiving data [asynchronously over the stream <em>s</em> +into the scatter/gather vector located in the <a href="/api/aio.html#asynchronous-io-handle"><code>nng_aio</code></a> <em>aio</em>, +which must have been previously set using <a href="/api/aio.html#scatter-gather-vectors"><code>nng_aio_set_iov</code></a>.</p> +<p>These functions return immediately, with no return value. +Completion of the operation is signaled via the <em>aio</em>, and the final +result may be obtained via <a href="/api/aio.html#result-of-operation"><code>nng_aio_result</code></a>.</p> +<p>The I/O operation may complete as soon as at least one byte has been +transferred, or an error has occurred. +Therefore, the number of bytes transferred may be less than requested. +The actual number of bytes transferred can be determined with <a href="/api/aio.html#result-of-operation"><code>nng_aio_count</code></a>.</p> +<h2 id="closing-a-stream"><a class="header" href="#closing-a-stream">Closing a Stream</a></h2> +<pre><code class="language-c">void nng_stream_close(nng_stream *s); +void nng_stream_stop(nng_stream *s); +void nng_stream_free(nng_stream *s); +</code></pre> +<p>The <a name="a005"></a><code>nng_stream_close</code> function closes a stream, but does not destroy it. +This function returns immediately. Operations that are pending against the stream, such +as <a href="/api/stream.html#sending-and-receiving-data"><code>nng_stream_send</code></a> or <a href="/api/stream.html#sending-and-receiving-data"><code>nng_stream_recv</code></a> operations will be canceled asynchronously, if possible. +Those operations will result in <a href="/api/errors.html#NNG_ECLOSED"><code>NNG_ECLOSED</code></a>.</p> +<p>The <a name="a006"></a><code>nng_stream_stop</code> function not only closes the stream, but waits for any operations +pending against it to complete, and for any underlying asynchronous registered I/O to be fully deregistered. +As some systems use separate threads for asynchronous I/O, stopping the stream is necessary before those +resources can be freed. Until the stream is stopped, there could still be I/O operations in flight, +making it unsafe to deallocate memory.</p> +<p>The <a name="a007"></a><code>nng_stream_free</code> function stops the stream like <code>nng_stream_stop</code>, but also deallocates the +stream itself.</p> +<div class="mdbook-alerts mdbook-alerts-note"> +<p class="mdbook-alerts-title"> + <span class="mdbook-alerts-icon"></span> + note +</p> +<p>Because <code>nng_stream_stop</code> and <code>nng_stream_free</code> both may block waiting for outstanding I/O to complete +or be aborted, these functions are unsafe to call from functions that may not block, such as the +completion function registered with an <a href="/api/aio.html#asynchronous-io-handle"><code>nng_aio</code></a> when it is created.</p> +</div> +<!-- Symbol cross reference --> +<!-- Macros --> +<!-- Protocols --> +<!-- Transports --> +<!-- Concept index --> + + </main> + + <nav class="nav-wrapper" aria-label="Page navigation"> + <!-- Mobile navigation buttons --> + <a rel="prev" href="../api/errors.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + <a rel="next prefetch" href="../api/misc.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + + <div style="clear: both"></div> + </nav> + </div> + </div> + + <nav class="nav-wide-wrapper" aria-label="Page navigation"> + <a rel="prev" href="../api/errors.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left"> + <i class="fa fa-angle-left"></i> + </a> + + <a rel="next prefetch" href="../api/misc.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right"> + <i class="fa fa-angle-right"></i> + </a> + </nav> + + </div> + + + + + <script> + window.playground_copyable = true; + </script> + + + <script src="../elasticlunr.min.js"></script> + <script src="../mark.min.js"></script> + <script src="../searcher.js"></script> + + <script src="../clipboard.min.js"></script> + <script src="../highlight.js"></script> + <script src="../book.js"></script> + + <!-- Custom JS scripts --> + <script src="../theme/pagetoc.js"></script> + + + </div> + </body> +</html> |