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+<body class="manpage">
+<div id="header">
+<h1>
+zmq_getsockopt(3) Manual Page
+</h1>
+<h2>NAME</h2>
+<div class="sectionbody">
+<p>zmq_getsockopt -
+ get 0MQ socket options
+</p>
+</div>
+</div>
+<div id="content">
+<div class="sect1">
+<h2 id="_synopsis">SYNOPSIS</h2>
+<div class="sectionbody">
+<div class="paragraph"><p><strong>int zmq_getsockopt (void <em>*socket</em>, int <em>option_name</em>, void <em>*option_value</em>, size_t <em>*option_len</em>);</strong></p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_description">DESCRIPTION</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>The <em>zmq_getsockopt()</em> function shall retrieve the value for the option
+specified by the <em>option_name</em> argument for the ØMQ socket pointed to by the
+<em>socket</em> argument, and store it in the buffer pointed to by the <em>option_value</em>
+argument. The <em>option_len</em> argument is the size in bytes of the buffer pointed
+to by <em>option_value</em>; upon successful completion <em>zmq_getsockopt()</em> shall
+modify the <em>option_len</em> argument to indicate the actual size of the option
+value stored in the buffer.</p></div>
+<div class="paragraph"><p>The following options can be retrieved with the <em>zmq_getsockopt()</em> function:</p></div>
+<div class="sect2">
+<h3 id="_zmq_type_retrieve_socket_type">ZMQ_TYPE: Retrieve socket type</h3>
+<div class="paragraph"><p>The <em>ZMQ_TYPE</em> option shall retrieve the socket type for the specified
+<em>socket</em>. The socket type is specified at socket creation time and
+cannot be modified afterwards.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_rcvmore_more_message_data_parts_to_follow">ZMQ_RCVMORE: More message data parts to follow</h3>
+<div class="paragraph"><p>The <em>ZMQ_RCVMORE</em> option shall return True (1) if the message part last
+received from the <em>socket</em> was a data part with more parts to follow. If there
+are no data parts to follow, this option shall return False (0).</p></div>
+<div class="paragraph"><p>Refer to <a href="zmq_send.html">zmq_send(3)</a> and <a href="zmq_recv.html">zmq_recv(3)</a> for a detailed description
+of multi-part messages.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+boolean
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_sndhwm_retrieves_high_water_mark_for_outbound_messages">ZMQ_SNDHWM: Retrieves high water mark for outbound messages</h3>
+<div class="paragraph"><p>The <em>ZMQ_SNDHWM</em> option shall return the high water mark for outbound messages
+on the specified <em>socket</em>. The high water mark is a hard limit on the maximum
+number of outstanding messages ØMQ shall queue in memory for any single peer
+that the specified <em>socket</em> is communicating with.</p></div>
+<div class="paragraph"><p>If this limit has been reached the socket shall enter an exceptional state and
+depending on the socket type, ØMQ shall take appropriate action such as
+blocking or dropping sent messages. Refer to the individual socket descriptions
+in <a href="zmq_socket.html">zmq_socket(3)</a> for details on the exact action taken for each socket
+type.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+messages
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+1000
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_rcvhwm_retrieve_high_water_mark_for_inbound_messages">ZMQ_RCVHWM: Retrieve high water mark for inbound messages</h3>
+<div class="paragraph"><p>The <em>ZMQ_RCVHWM</em> option shall return the high water mark for inbound messages on
+the specified <em>socket</em>. The high water mark is a hard limit on the maximum
+number of outstanding messages ØMQ shall queue in memory for any single peer
+that the specified <em>socket</em> is communicating with.</p></div>
+<div class="paragraph"><p>If this limit has been reached the socket shall enter an exceptional state and
+depending on the socket type, ØMQ shall take appropriate action such as
+blocking or dropping sent messages. Refer to the individual socket descriptions
+in <a href="zmq_socket.html">zmq_socket(3)</a> for details on the exact action taken for each socket
+type.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+messages
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+1000
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_affinity_retrieve_i_o_thread_affinity">ZMQ_AFFINITY: Retrieve I/O thread affinity</h3>
+<div class="paragraph"><p>The <em>ZMQ_AFFINITY</em> option shall retrieve the I/O thread affinity for newly
+created connections on the specified <em>socket</em>.</p></div>
+<div class="paragraph"><p>Affinity determines which threads from the ØMQ I/O thread pool associated with
+the socket’s <em>context</em> shall handle newly created connections. A value of zero
+specifies no affinity, meaning that work shall be distributed fairly among all
+ØMQ I/O threads in the thread pool. For non-zero values, the lowest bit
+corresponds to thread 1, second lowest bit to thread 2 and so on. For example,
+a value of 3 specifies that subsequent connections on <em>socket</em> shall be handled
+exclusively by I/O threads 1 and 2.</p></div>
+<div class="paragraph"><p>See also <a href="zmq_init.html">zmq_init(3)</a> for details on allocating the number of I/O
+threads for a specific <em>context</em>.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+uint64_t
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A (bitmap)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+0
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_identity_set_socket_identity">ZMQ_IDENTITY: Set socket identity</h3>
+<div class="paragraph"><p>The <em>ZMQ_IDENTITY</em> option shall retrieve the identity of the specified <em>socket</em>.
+Socket identity is used only by request/reply pattern. Namely, it can be used
+in tandem with ROUTER socket to route messages to the peer with specific
+identity.</p></div>
+<div class="paragraph"><p>Identity should be at least one byte and at most 255 bytes long. Identities
+starting with binary zero are reserved for use by ØMQ infrastructure.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+binary data
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+NULL
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_rate_retrieve_multicast_data_rate">ZMQ_RATE: Retrieve multicast data rate</h3>
+<div class="paragraph"><p>The <em>ZMQ_RATE</em> option shall retrieve the maximum send or receive data rate for
+multicast transports using the specified <em>socket</em>.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+kilobits per second
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+100
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using multicast transports
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_recovery_ivl_get_multicast_recovery_interval">ZMQ_RECOVERY_IVL: Get multicast recovery interval</h3>
+<div class="paragraph"><p>The <em>ZMQ_RECOVERY_IVL</em> option shall retrieve the recovery interval for
+multicast transports using the specified <em>socket</em>. The recovery interval
+determines the maximum time in milliseconds that a receiver can be absent from a
+multicast group before unrecoverable data loss will occur.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+milliseconds
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+10000
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using multicast transports
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_sndbuf_retrieve_kernel_transmit_buffer_size">ZMQ_SNDBUF: Retrieve kernel transmit buffer size</h3>
+<div class="paragraph"><p>The <em>ZMQ_SNDBUF</em> option shall retrieve the underlying kernel transmit buffer
+size for the specified <em>socket</em>. A value of zero means that the OS default is
+in effect. For details refer to your operating system documentation for the
+<em>SO_SNDBUF</em> socket option.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+bytes
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+0
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_rcvbuf_retrieve_kernel_receive_buffer_size">ZMQ_RCVBUF: Retrieve kernel receive buffer size</h3>
+<div class="paragraph"><p>The <em>ZMQ_RCVBUF</em> option shall retrieve the underlying kernel receive buffer
+size for the specified <em>socket</em>. A value of zero means that the OS default is
+in effect. For details refer to your operating system documentation for the
+<em>SO_RCVBUF</em> socket option.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+bytes
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+0
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_linger_retrieve_linger_period_for_socket_shutdown">ZMQ_LINGER: Retrieve linger period for socket shutdown</h3>
+<div class="paragraph"><p>The <em>ZMQ_LINGER</em> option shall retrieve the linger period for the specified
+<em>socket</em>. The linger period determines how long pending messages which have
+yet to be sent to a peer shall linger in memory after a socket is closed with
+<a href="zmq_close.html">zmq_close(3)</a>, and further affects the termination of the socket’s
+context with <a href="zmq_term.html">zmq_term(3)</a>. The following outlines the different
+behaviours:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+The default value of <em>-1</em> specifies an infinite linger period. Pending
+ messages shall not be discarded after a call to <em>zmq_close()</em>; attempting to
+ terminate the socket’s context with <em>zmq_term()</em> shall block until all
+ pending messages have been sent to a peer.
+</p>
+</li>
+<li>
+<p>
+The value of <em>0</em> specifies no linger period. Pending messages shall be
+ discarded immediately when the socket is closed with <em>zmq_close()</em>.
+</p>
+</li>
+<li>
+<p>
+Positive values specify an upper bound for the linger period in milliseconds.
+ Pending messages shall not be discarded after a call to <em>zmq_close()</em>;
+ attempting to terminate the socket’s context with <em>zmq_term()</em> shall block
+ until either all pending messages have been sent to a peer, or the linger
+ period expires, after which any pending messages shall be discarded.
+</p>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+milliseconds
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1 (infinite)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</li>
+</ul></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_reconnect_ivl_retrieve_reconnection_interval">ZMQ_RECONNECT_IVL: Retrieve reconnection interval</h3>
+<div class="paragraph"><p>The <em>ZMQ_RECONNECT_IVL</em> option shall retrieve the initial reconnection interval
+for the specified <em>socket</em>. The reconnection interval is the period ØMQ shall
+wait between attempts to reconnect disconnected peers when using
+connection-oriented transports. The value -1 means no reconnection.</p></div>
+<div class="admonitionblock">
+<table><tr>
+<td class="icon">
+<div class="title">Note</div>
+</td>
+<td class="content">The reconnection interval may be randomized by ØMQ to prevent
+reconnection storms in topologies with a large number of peers per socket.</td>
+</tr></table>
+</div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+milliseconds
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+100
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, only for connection-oriented transports
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_reconnect_ivl_max_retrieve_maximum_reconnection_interval">ZMQ_RECONNECT_IVL_MAX: Retrieve maximum reconnection interval</h3>
+<div class="paragraph"><p>The <em>ZMQ_RECONNECT_IVL_MAX</em> option shall retrieve the maximum reconnection
+interval for the specified <em>socket</em>. This is the maximum period ØMQ shall wait
+between attempts to reconnect. On each reconnect attempt, the previous interval
+shall be doubled untill ZMQ_RECONNECT_IVL_MAX is reached. This allows for
+exponential backoff strategy. Default value means no exponential backoff is
+performed and reconnect interval calculations are only based on
+ZMQ_RECONNECT_IVL.</p></div>
+<div class="admonitionblock">
+<table><tr>
+<td class="icon">
+<div class="title">Note</div>
+</td>
+<td class="content">Values less than ZMQ_RECONNECT_IVL will be ignored.</td>
+</tr></table>
+</div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+milliseconds
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+0 (only use ZMQ_RECONNECT_IVL)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, only for connection-oriented transport
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_backlog_retrieve_maximum_length_of_the_queue_of_outstanding_connections">ZMQ_BACKLOG: Retrieve maximum length of the queue of outstanding connections</h3>
+<div class="paragraph"><p>The <em>ZMQ_BACKLOG</em> option shall retrieve the maximum length of the queue of
+outstanding peer connections for the specified <em>socket</em>; this only applies to
+connection-oriented transports. For details refer to your operating system
+documentation for the <em>listen</em> function.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+connections
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+100
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, only for connection-oriented transports
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_maxmsgsize_maximum_acceptable_inbound_message_size">ZMQ_MAXMSGSIZE: Maximum acceptable inbound message size</h3>
+<div class="paragraph"><p>The option shall retrieve limit for the inbound messages. If a peer sends
+a message larger than ZMQ_MAXMSGSIZE it is disconnected. Value of -1 means
+<em>no limit</em>.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int64_t
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+bytes
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_multicast_hops_maximum_network_hops_for_multicast_packets">ZMQ_MULTICAST_HOPS: Maximum network hops for multicast packets</h3>
+<div class="paragraph"><p>The option shall retrieve time-to-live used for outbound multicast packets.
+The default of 1 means that the multicast packets don’t leave the local network.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+network hops
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+1
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using multicast transports
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_rcvtimeo_maximum_time_before_a_socket_operation_returns_with_eagain">ZMQ_RCVTIMEO: Maximum time before a socket operation returns with EAGAIN</h3>
+<div class="paragraph"><p>Retrieve the timeout for recv operation on the socket. If the value is <tt>0</tt>,
+<em>zmq_recv(3)</em> will return immediately, with a EAGAIN error if there is no
+message to receive. If the value is <tt>-1</tt>, it will block until a message is
+available. For all other values, it will wait for a message for that amount
+of time before returning with an EAGAIN error.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+milliseconds
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1 (infinite)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_sndtimeo_maximum_time_before_a_socket_operation_returns_with_eagain">ZMQ_SNDTIMEO: Maximum time before a socket operation returns with EAGAIN</h3>
+<div class="paragraph"><p>Retrieve the timeout for send operation on the socket. If the value is <tt>0</tt>,
+<em>zmq_send(3)</em> will return immediately, with a EAGAIN error if the message
+cannot be sent. If the value is <tt>-1</tt>, it will block until the message is sent.
+For all other values, it will try to send the message for that amount of time
+before returning with an EAGAIN error.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+milliseconds
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1 (infinite)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_ipv4only_retrieve_ipv4_only_socket_override_status">ZMQ_IPV4ONLY: Retrieve IPv4-only socket override status</h3>
+<div class="paragraph"><p>Retrieve the underlying native socket type. A value of <tt>1</tt> will use IPv4
+sockets, while the value of <tt>0</tt> will use IPv6 sockets. An IPv6 socket
+lets applications connect to and accept connections from both IPv4 and IPv6
+hosts.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+boolean
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+1 (true)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using TCP transports.
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_delay_attach_on_connect_retrieve_attach_on_connect_value">ZMQ_DELAY_ATTACH_ON_CONNECT: Retrieve attach-on-connect value</h3>
+<div class="paragraph"><p>Retrieve the state of the attach on connect value. If set to <tt>1</tt>, will delay the
+attachment of a pipe on connect until the underlying connection has completed.
+This will cause the socket to block if there are no other connections, but will
+prevent queues from filling on pipes awaiting connection.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+boolean
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+0 (false)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, primarily when using TCP/IPC transports.
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_fd_retrieve_file_descriptor_associated_with_the_socket">ZMQ_FD: Retrieve file descriptor associated with the socket</h3>
+<div class="paragraph"><p>The <em>ZMQ_FD</em> option shall retrieve the file descriptor associated with the
+specified <em>socket</em>. The returned file descriptor can be used to integrate the
+socket into an existing event loop; the ØMQ library shall signal any pending
+events on the socket in an <em>edge-triggered</em> fashion by making the file
+descriptor become ready for reading.</p></div>
+<div class="admonitionblock">
+<table><tr>
+<td class="icon">
+<div class="title">Note</div>
+</td>
+<td class="content">The ability to read from the returned file descriptor does not
+necessarily indicate that messages are available to be read from, or can be
+written to, the underlying socket; applications must retrieve the actual event
+state with a subsequent retrieval of the <em>ZMQ_EVENTS</em> option.</td>
+</tr></table>
+</div>
+<div class="admonitionblock">
+<table><tr>
+<td class="icon">
+<div class="title">Note</div>
+</td>
+<td class="content">The returned file descriptor is also used internally by the <em>zmq_send</em>
+and <em>zmq_recv</em> functions. As the descriptor is edge triggered, applications
+must update the state of <em>ZMQ_EVENTS</em> after each invocation of <em>zmq_send</em>
+or <em>zmq_recv</em>.To be more explicit: after calling <em>zmq_send</em> the socket may
+become readable (and vice versa) without triggering a read event on the
+file descriptor.</td>
+</tr></table>
+</div>
+<div class="admonitionblock">
+<table><tr>
+<td class="icon">
+<div class="title">Caution</div>
+</td>
+<td class="content">The returned file descriptor is intended for use with a <em>poll</em> or
+similar system call only. Applications must never attempt to read or write data
+to it directly, neither should they try to close it.</td>
+</tr></table>
+</div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int on POSIX systems, SOCKET on Windows
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_events_retrieve_socket_event_state">ZMQ_EVENTS: Retrieve socket event state</h3>
+<div class="paragraph"><p>The <em>ZMQ_EVENTS</em> option shall retrieve the event state for the specified
+<em>socket</em>. The returned value is a bit mask constructed by OR’ing a combination
+of the following event flags:</p></div>
+<div class="dlist"><dl>
+<dt class="hdlist1">
+<strong>ZMQ_POLLIN</strong>
+</dt>
+<dd>
+<p>
+Indicates that at least one message may be received from the specified socket
+without blocking.
+</p>
+</dd>
+<dt class="hdlist1">
+<strong>ZMQ_POLLOUT</strong>
+</dt>
+<dd>
+<p>
+Indicates that at least one message may be sent to the specified socket without
+blocking.
+</p>
+</dd>
+</dl></div>
+<div class="paragraph"><p>The combination of a file descriptor returned by the <em>ZMQ_FD</em> option being
+ready for reading but no actual events returned by a subsequent retrieval of
+the <em>ZMQ_EVENTS</em> option is valid; applications should simply ignore this case
+and restart their polling operation/event loop.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A (flags)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_last_endpoint_retrieve_the_last_endpoint_set">ZMQ_LAST_ENDPOINT: Retrieve the last endpoint set</h3>
+<div class="paragraph"><p>The <em>ZMQ_LAST_ENDPOINT</em> option shall retrieve the last endpoint bound for
+TCP and IPC transports. The returned value will be a string in the form of
+a ZMQ DSN. Note that if the TCP host is INADDR_ANY, indicated by a *, then
+the returned address will be 0.0.0.0 (for IPv4).</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+character string
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+N/A
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+NULL
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when binding TCP or IPC transports
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_tcp_keepalive_override_so_keepalive_socket_option">ZMQ_TCP_KEEPALIVE: Override SO_KEEPALIVE socket option</h3>
+<div class="paragraph"><p>Override <em>SO_KEEPALIVE</em> socket option(where supported by OS).
+The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1,0,1
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1 (leave to OS default)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using TCP transports.
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_tcp_keepalive_idle_override_tcp_keepcnt_or_tcp_keepalive_on_some_os">ZMQ_TCP_KEEPALIVE_IDLE: Override TCP_KEEPCNT(or TCP_KEEPALIVE on some OS)</h3>
+<div class="paragraph"><p>Override <em>TCP_KEEPCNT</em>(or <em>TCP_KEEPALIVE</em> on some OS) socket option(where supported by OS).
+The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1,>0
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1 (leave to OS default)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using TCP transports.
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_tcp_keepalive_cnt_override_tcp_keepcnt_socket_option">ZMQ_TCP_KEEPALIVE_CNT: Override TCP_KEEPCNT socket option</h3>
+<div class="paragraph"><p>Override <em>TCP_KEEPCNT</em> socket option(where supported by OS).
+The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1,>0
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1 (leave to OS default)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using TCP transports.
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+<div class="sect2">
+<h3 id="_zmq_tcp_keepalive_intvl_override_tcp_keepintvl_socket_option">ZMQ_TCP_KEEPALIVE_INTVL: Override TCP_KEEPINTVL socket option</h3>
+<div class="paragraph"><p>Override <em>TCP_KEEPINTVL</em> socket option(where supported by OS).
+The default value of <tt>-1</tt> means to skip any overrides and leave it to OS default.</p></div>
+<div class="hdlist"><table>
+<tr>
+<td class="hdlist1">
+Option value type
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+int
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Option value unit
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1,>0
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Default value
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+-1 (leave to OS default)
+</p>
+</td>
+</tr>
+<tr>
+<td class="hdlist1">
+Applicable socket types
+<br />
+</td>
+<td class="hdlist2">
+<p style="margin-top: 0;">
+all, when using TCP transports.
+</p>
+</td>
+</tr>
+</table></div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_return_value">RETURN VALUE</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>The <em>zmq_getsockopt()</em> function shall return zero if successful. Otherwise it
+shall return <tt>-1</tt> and set <em>errno</em> to one of the values defined below.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_errors">ERRORS</h2>
+<div class="sectionbody">
+<div class="dlist"><dl>
+<dt class="hdlist1">
+<strong>EINVAL</strong>
+</dt>
+<dd>
+<p>
+The requested option <em>option_name</em> is unknown, or the requested <em>option_len</em> or
+<em>option_value</em> is invalid, or the size of the buffer pointed to by
+<em>option_value</em>, as specified by <em>option_len</em>, is insufficient for storing the
+option value.
+</p>
+</dd>
+<dt class="hdlist1">
+<strong>ETERM</strong>
+</dt>
+<dd>
+<p>
+The ØMQ <em>context</em> associated with the specified <em>socket</em> was terminated.
+</p>
+</dd>
+<dt class="hdlist1">
+<strong>ENOTSOCK</strong>
+</dt>
+<dd>
+<p>
+The provided <em>socket</em> was invalid.
+</p>
+</dd>
+<dt class="hdlist1">
+<strong>EINTR</strong>
+</dt>
+<dd>
+<p>
+The operation was interrupted by delivery of a signal.
+</p>
+</dd>
+</dl></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_example">EXAMPLE</h2>
+<div class="sectionbody">
+<div class="listingblock">
+<div class="title">Retrieving the high water mark for outgoing messages</div>
+<div class="content">
+<pre><tt>/* Retrieve high water mark into sndhwm */
+int sndhwm;
+size_t sndhwm_size = sizeof (sndhwm);
+rc = zmq_getsockopt (socket, ZMQ_SNDHWM, &sndhwm, &sndhwm_size);
+assert (rc == 0);</tt></pre>
+</div></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_see_also">SEE ALSO</h2>
+<div class="sectionbody">
+<div class="paragraph"><p><a href="zmq_setsockopt.html">zmq_setsockopt(3)</a>
+<a href="zmq_socket.html">zmq_socket(3)</a>
+<a href="zmq.html">zmq(7)</a></p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_authors">AUTHORS</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>This ØMQ manual page was written by Martin Sustrik <<a href="mailto:sustrik@250bpm.com">sustrik@250bpm.com</a>> and
+Martin Lucina <<a href="mailto:mato@kotelna.sk">mato@kotelna.sk</a>>.</p></div>
+</div>
+</div>
+</div>
+<div id="footnotes"><hr /></div>
+<div id="footer">
+<div id="footer-text">
+ØMQ 3.2.2<br />
+Last updated 2012-11-14 10:09:14 KST
+</div>
+</div>
+</body>
+</html>
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