diff options
| author | Martin Lucina <martin@lucina.net> | 2012-01-23 08:53:41 +0100 |
|---|---|---|
| committer | Martin Lucina <martin@lucina.net> | 2012-01-23 08:53:41 +0100 |
| commit | 8e61b98c5e2943b149c825310b24e714a6127072 (patch) | |
| tree | a31c049de7a86278ab17df3e0579944f6f524f7d /doc/zmq_socket.html | |
| parent | e645fc2693acc796304498909786b7b47005b429 (diff) | |
Imported Upstream version 2.1.4upstream/2.1.4
Diffstat (limited to 'doc/zmq_socket.html')
| -rw-r--r-- | doc/zmq_socket.html | 1416 |
1 files changed, 1416 insertions, 0 deletions
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+<body>
+<div id="header">
+<h1>
+zmq_socket(3) Manual Page
+</h1>
+<h2>NAME</h2>
+<div class="sectionbody">
+<p>zmq_socket -
+ create 0MQ socket
+</p>
+</div>
+</div>
+<div id="content">
+<h2 id="_synopsis">SYNOPSIS</h2>
+<div class="sectionbody">
+<div class="paragraph"><p><strong>void *zmq_socket (void <em>*context</em>, int <em>type</em>);</strong></p></div>
+</div>
+<h2 id="_description">DESCRIPTION</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>The <em>zmq_socket()</em> function shall create a ØMQ socket within the specified
+<em>context</em> and return an opaque handle to the newly created socket. The <em>type</em>
+argument specifies the socket type, which determines the semantics of
+communication over the socket.</p></div>
+<div class="paragraph"><p>The newly created socket is initially unbound, and not associated with any
+endpoints. In order to establish a message flow a socket must first be
+connected to at least one endpoint with <a href="zmq_connect.html">zmq_connect(3)</a>, or at least one
+endpoint must be created for accepting incoming connections with
+<a href="zmq_bind.html">zmq_bind(3)</a>.</p></div>
+<div class="paragraph"><div class="title">Key differences to conventional sockets</div><p>Generally speaking, conventional sockets present a <em>synchronous</em> interface to
+either connection-oriented reliable byte streams (SOCK_STREAM), or
+connection-less unreliable datagrams (SOCK_DGRAM). In comparison, ØMQ sockets
+present an abstraction of an asynchronous <em>message queue</em>, with the exact
+queueing semantics depending on the socket type in use. Where conventional
+sockets transfer streams of bytes or discrete datagrams, ØMQ sockets transfer
+discrete <em>messages</em>.</p></div>
+<div class="paragraph"><p>ØMQ sockets being <em>asynchronous</em> means that the timings of the physical
+connection setup and tear down, reconnect and effective delivery are transparent
+to the user and organized by ØMQ itself. Further, messages may be <em>queued</em> in
+the event that a peer is unavailable to receive them.</p></div>
+<div class="paragraph"><p>Conventional sockets allow only strict one-to-one (two peers), many-to-one
+(many clients, one server), or in some cases one-to-many (multicast)
+relationships. With the exception of <em>ZMQ_PAIR</em>, ØMQ sockets may be connected
+<strong>to multiple endpoints</strong> using <em>zmq_connect()</em>, while simultaneously accepting
+incoming connections <strong>from multiple endpoints</strong> bound to the socket using
+<em>zmq_bind()</em>, thus allowing many-to-many relationships.</p></div>
+<div class="paragraph"><div class="title">Thread safety</div><p>ØMQ <em>sockets</em> are <em>not</em> thread safe. Applications MUST NOT use a socket
+from multiple threads except after migrating a socket from one thread to
+another with a "full fence" memory barrier.</p></div>
+<div class="paragraph"><div class="title">Socket types</div><p>The following sections present the socket types defined by ØMQ, grouped by the
+general <em>messaging pattern</em> which is built from related socket types.</p></div>
+<h3 id="_request_reply_pattern">Request-reply pattern</h3><div style="clear:left"></div>
+<div class="paragraph"><p>The request-reply pattern is used for sending requests from a <em>client</em> to one
+or more instances of a <em>service</em>, and receiving subsequent replies to each
+request sent.</p></div>
+<h4 id="_zmq_req">ZMQ_REQ</h4>
+<div class="paragraph"><p>A socket of type <em>ZMQ_REQ</em> is used by a <em>client</em> to send requests to and
+receive replies from a <em>service</em>. This socket type allows only an alternating
+sequence of <em>zmq_send(request)</em> and subsequent <em>zmq_recv(reply)</em> calls. Each
+request sent is load-balanced among all <em>services</em>, and each reply received is
+matched with the last issued request.</p></div>
+<div class="paragraph"><p>When a <em>ZMQ_REQ</em> socket enters an exceptional state due to having reached the
+high water mark for all <em>services</em>, or if there are no <em>services</em> at all, then
+any <a href="zmq_send.html">zmq_send(3)</a> operations on the socket shall block until the
+exceptional state ends or at least one <em>service</em> becomes available for sending;
+messages are not discarded.</p></div>
+<div class="hdlist"><div class="title">Summary of ZMQ_REQ characteristics</div><table>
+<tr>
+<td class="hdlist1">
+Compatible peer sockets
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+<em>ZMQ_REP</em>
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Direction
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Bidirectional
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Send/receive pattern
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Send, Receive, Send, Receive, …
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Outgoing routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Load-balanced
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Incoming routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Last peer
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+ZMQ_HWM option action
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Block
+</p>
+</td>
+</tr>
+</table></div>
+<h4 id="_zmq_rep">ZMQ_REP</h4>
+<div class="paragraph"><p>A socket of type <em>ZMQ_REP</em> is used by a <em>service</em> to receive requests from and
+send replies to a <em>client</em>. This socket type allows only an alternating
+sequence of <em>zmq_recv(request)</em> and subsequent <em>zmq_send(reply)</em> calls. Each
+request received is fair-queued from among all <em>clients</em>, and each reply sent
+is routed to the <em>client</em> that issued the last request. If the original
+requester doesn’t exist any more the reply is silently discarded.</p></div>
+<div class="paragraph"><p>When a <em>ZMQ_REP</em> socket enters an exceptional state due to having reached the
+high water mark for a <em>client</em>, then any replies sent to the <em>client</em> in
+question shall be dropped until the exceptional state ends.</p></div>
+<div class="hdlist"><div class="title">Summary of ZMQ_REP characteristics</div><table>
+<tr>
+<td class="hdlist1">
+Compatible peer sockets
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+<em>ZMQ_REQ</em>
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Direction
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Bidirectional
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Send/receive pattern
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Receive, Send, Receive, Send, …
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Incoming routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Fair-queued
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Outgoing routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Last peer
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+ZMQ_HWM option action
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Drop
+</p>
+</td>
+</tr>
+</table></div>
+<h4 id="_zmq_dealer">ZMQ_DEALER</h4>
+<div class="paragraph"><p>A socket of type <em>ZMQ_DEALER</em> is an advanced pattern used for extending
+request/reply sockets. Each message sent is load-balanced among all connected
+peers, and each message received is fair-queued from all connected peers.</p></div>
+<div class="paragraph"><p>Previously this socket was called <em>ZMQ_XREQ</em> and that name remains available
+for backwards compatibility.</p></div>
+<div class="paragraph"><p>When a <em>ZMQ_DEALER</em> socket enters an exceptional state due to having reached the
+high water mark for all peers, or if there are no peers at all, then any
+<a href="zmq_send.html">zmq_send(3)</a> operations on the socket shall block until the exceptional
+state ends or at least one peer becomes available for sending; messages are not
+discarded.</p></div>
+<div class="paragraph"><p>When a <em>ZMQ_DEALER</em> socket is connected to a <em>ZMQ_REP</em> socket each message sent
+must consist of an empty message part, the <em>delimiter</em>, followed by one or more
+<em>body parts</em>.</p></div>
+<div class="hdlist"><div class="title">Summary of ZMQ_DEALER characteristics</div><table>
+<tr>
+<td class="hdlist1">
+Compatible peer sockets
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+<em>ZMQ_ROUTER</em>, <em>ZMQ_REP</em>
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Direction
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Bidirectional
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Send/receive pattern
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Unrestricted
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Outgoing routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Load-balanced
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Incoming routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Fair-queued
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+ZMQ_HWM option action
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Block
+</p>
+</td>
+</tr>
+</table></div>
+<h4 id="_zmq_router">ZMQ_ROUTER</h4>
+<div class="paragraph"><p>A socket of type <em>ZMQ_ROUTER</em> is an advanced pattern used for extending
+request/reply sockets. When receiving messages a <em>ZMQ_ROUTER</em> socket shall
+prepend a message part containing the <em>identity</em> of the originating peer to the
+message before passing it to the application. Messages received are fair-queued
+from among all connected peers. When sending messages a <em>ZMQ_ROUTER</em> socket shall
+remove the first part of the message and use it to determine the <em>identity</em> of
+the peer the message shall be routed to. If the peer does not exist anymore
+the message shall be silently discarded.</p></div>
+<div class="paragraph"><p>Previously this socket was called <em>ZMQ_XREP</em> and that name remains available
+for backwards compatibility.</p></div>
+<div class="paragraph"><p>When a <em>ZMQ_ROUTER</em> socket enters an exceptional state due to having reached the
+high water mark for all peers, or if there are no peers at all, then any
+messages sent to the socket shall be dropped until the exceptional state ends.
+Likewise, any messages routed to a non-existent peer or a peer for which the
+individual high water mark has been reached shall also be dropped.</p></div>
+<div class="paragraph"><p>When a <em>ZMQ_REQ</em> socket is connected to a <em>ZMQ_ROUTER</em> socket, in addition to the
+<em>identity</em> of the originating peer each message received shall contain an empty
+<em>delimiter</em> message part. Hence, the entire structure of each received message
+as seen by the application becomes: one or more <em>identity</em> parts, <em>delimiter</em>
+part, one or more <em>body parts</em>. When sending replies to a <em>ZMQ_REQ</em> socket the
+application must include the <em>delimiter</em> part.</p></div>
+<div class="hdlist"><div class="title">Summary of ZMQ_ROUTER characteristics</div><table>
+<tr>
+<td class="hdlist1">
+Compatible peer sockets
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+<em>ZMQ_DEALER</em>, <em>ZMQ_REQ</em>
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Direction
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Bidirectional
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Send/receive pattern
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Unrestricted
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Outgoing routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+See text
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Incoming routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Fair-queued
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+ZMQ_HWM option action
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Drop
+</p>
+</td>
+</tr>
+</table></div>
+<h3 id="_publish_subscribe_pattern">Publish-subscribe pattern</h3><div style="clear:left"></div>
+<div class="paragraph"><p>The publish-subscribe pattern is used for one-to-many distribution of data from
+a single <em>publisher</em> to multiple <em>subscribers</em> in a fan out fashion.</p></div>
+<h4 id="_zmq_pub">ZMQ_PUB</h4>
+<div class="paragraph"><p>A socket of type <em>ZMQ_PUB</em> is used by a <em>publisher</em> to distribute data.
+Messages sent are distributed in a fan out fashion to all connected peers.
+The <a href="zmq_recv.html">zmq_recv(3)</a> function is not implemented for this socket type.</p></div>
+<div class="paragraph"><p>When a <em>ZMQ_PUB</em> socket enters an exceptional state due to having reached the
+high water mark for a <em>subscriber</em>, then any messages that would be sent to the
+<em>subscriber</em> in question shall instead be dropped until the exceptional state
+ends. The <em>zmq_send()</em> function shall never block for this socket type.</p></div>
+<div class="hdlist"><div class="title">Summary of ZMQ_PUB characteristics</div><table>
+<tr>
+<td class="hdlist1">
+Compatible peer sockets
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+<em>ZMQ_SUB</em>
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Direction
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Unidirectional
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Send/receive pattern
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Send only
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Incoming routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Outgoing routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Fan out
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+ZMQ_HWM option action
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Drop
+</p>
+</td>
+</tr>
+</table></div>
+<h4 id="_zmq_sub">ZMQ_SUB</h4>
+<div class="paragraph"><p>A socket of type <em>ZMQ_SUB</em> is used by a <em>subscriber</em> to subscribe to data
+distributed by a <em>publisher</em>. Initially a <em>ZMQ_SUB</em> socket is not subscribed to
+any messages, use the <em>ZMQ_SUBSCRIBE</em> option of <a href="zmq_setsockopt.html">zmq_setsockopt(3)</a> to
+specify which messages to subscribe to. The <em>zmq_send()</em> function is not
+implemented for this socket type.</p></div>
+<div class="hdlist"><div class="title">Summary of ZMQ_SUB characteristics</div><table>
+<tr>
+<td class="hdlist1">
+Compatible peer sockets
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+<em>ZMQ_PUB</em>
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Direction
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Unidirectional
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Send/receive pattern
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Receive only
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Incoming routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Fair-queued
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Outgoing routing strategy
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+ZMQ_HWM option action
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+Drop
+</p>
+</td>
+</tr>
+</table></div>
+<h3 id="_pipeline_pattern">Pipeline pattern</h3><div style="clear:left"></div>
+<div class="paragraph"><p>The pipeline pattern is used for distributing data to <em>nodes</em> arranged in
+a pipeline. Data always flows down the pipeline, and each stage of the pipeline
+is connected to at least one <em>node</em>. When a pipeline stage is connected to
+multiple <em>nodes</em> data is load-balanced among all connected <em& |