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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head><meta name="generator" content="HTML Tidy, see www.w3.org"><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link type="text/css" rel="stylesheet" href="style.css"><!-- Generated by The Open Group's rhtm tool v1.2.1 --><!-- Copyright (c) 2001-2003 The Open Group, All Rights Reserved --><title>setsockopt</title></head><body bgcolor="white"><basefont size="3"> <a name="setsockopt"></a> <a name="tag_03_668"></a><!-- setsockopt --> <!--header start--><center><font size="2">The Open Group Base Specifications Issue 6<br>IEEE Std 1003.1, 2003 Edition<br>Copyright © 2001-2003 The IEEE and The Open Group, All Rights reserved.</font></center><!--header end--><hr size="2" noshade><h4><a name="tag_03_668_01"></a>NAME</h4><blockquote>setsockopt - set the socket options</blockquote><h4><a name="tag_03_668_02"></a>SYNOPSIS</h4><blockquote class="synopsis"><p><code><tt>#include <<a href="../basedefs/sys/socket.h.html">sys/socket.h</a>><br><br> int setsockopt(int</tt> <i>socket</i><tt>, int</tt> <i>level</i><tt>, int</tt> <i>option_name</i><tt>,<br> const void *</tt><i>option_value</i><tt>, socklen_t</tt> <i>option_len</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_668_03"></a>DESCRIPTION</h4><blockquote><p>The <i>setsockopt</i>() function shall set the option specified by the <i>option_name</i> argument, at the protocol levelspecified by the <i>level</i> argument, to the value pointed to by the <i>option_value</i> argument for the socket associated withthe file descriptor specified by the <i>socket</i> argument.</p><p>The <i>level</i> argument specifies the protocol level at which the option resides. To set options at the socket level, specifythe <i>level</i> argument as SOL_SOCKET. To set options at other levels, supply the appropriate <i>level</i> identifier for theprotocol controlling the option. For example, to indicate that an option is interpreted by the TCP (Transport Control Protocol),set <i>level</i> to IPPROTO_TCP as defined in the <a href="../basedefs/netinet/in.h.html"><i><netinet/in.h></i></a>header.</p><p>The <i>option_name</i> argument specifies a single option to set. The <i>option_name</i> argument and any specified options arepassed uninterpreted to the appropriate protocol module for interpretations. The <a href="../basedefs/sys/socket.h.html"><i><sys/socket.h></i></a> header defines the socket-level options. The options are asfollows:</p><dl compact><dt>SO_DEBUG</dt><dd>Turns on recording of debugging information. This option enables or disables debugging in the underlying protocol modules. Thisoption takes an <b>int</b> value. This is a Boolean option.</dd><dt>SO_BROADCAST</dt><dd>Permits sending of broadcast messages, if this is supported by the protocol. This option takes an <b>int</b> value. This is aBoolean option.</dd><dt>SO_REUSEADDR</dt><dd>Specifies that the rules used in validating addresses supplied to <a href="../functions/bind.html"><i>bind</i>()</a> shouldallow reuse of local addresses, if this is supported by the protocol. This option takes an <b>int</b> value. This is a Booleanoption.</dd><dt>SO_KEEPALIVE</dt><dd>Keeps connections active by enabling the periodic transmission of messages, if this is supported by the protocol. This optiontakes an <b>int</b> value. <p>If the connected socket fails to respond to these messages, the connection is broken and threads writing to that socket arenotified with a SIGPIPE signal. This is a Boolean option.</p></dd><dt>SO_LINGER</dt><dd>Lingers on a <a href="../functions/close.html"><i>close</i>()</a> if data is present. This option controls the action takenwhen unsent messages queue on a socket and <a href="../functions/close.html"><i>close</i>()</a> is performed. If SO_LINGER is set,the system shall block the process during <a href="../functions/close.html"><i>close</i>()</a> until it can transmit the data oruntil the time expires. If SO_LINGER is not specified, and <a href="../functions/close.html"><i>close</i>()</a> is issued, thesystem handles the call in a way that allows the process to continue as quickly as possible. This option takes a <b>linger</b>structure, as defined in the <a href="../basedefs/sys/socket.h.html"><i><sys/socket.h></i></a> header, to specify the stateof the option and linger interval.</dd><dt>SO_OOBINLINE</dt><dd>Leaves received out-of-band data (data marked urgent) inline. This option takes an <b>int</b> value. This is a Booleanoption.</dd><dt>SO_SNDBUF</dt><dd>Sets send buffer size. This option takes an <b>int</b> value.</dd><dt>SO_RCVBUF</dt><dd>Sets receive buffer size. This option takes an <b>int</b> value.</dd><dt>SO_DONTROUTE</dt><dd>Requests that outgoing messages bypass the standard routing facilities. The destination shall be on a directly-connectednetwork, and messages are directed to the appropriate network interface according to the destination address. The effect, if any,of this option depends on what protocol is in use. This option takes an <b>int</b> value. This is a Boolean option.</dd><dt>SO_RCVLOWAT</dt><dd>Sets the minimum number of bytes to process for socket input operations. The default value for SO_RCVLOWAT is 1. If SO_RCVLOWATis set to a larger value, blocking receive calls normally wait until they have received the smaller of the low water mark value orthe requested amount. (They may return less than the low water mark if an error occurs, a signal is caught, or the type of datanext in the receive queue is different from that returned; for example, out-of-band data.) This option takes an <b>int</b> value.Note that not all implementations allow this option to be set.</dd><dt>SO_RCVTIMEO</dt><dd>Sets the timeout value that specifies the maximum amount of time an input function waits until it completes. It accepts a<b>timeval</b> structure with the number of seconds and microseconds specifying the limit on how long to wait for an inputoperation to complete. If a receive operation has blocked for this much time without receiving additional data, it shall returnwith a partial count or <i>errno</i> set to [EAGAIN] or [EWOULDBLOCK] if no data is received. The default for this option is zero,which indicates that a receive operation shall not time out. This option takes a <b>timeval</b> structure. Note that not allimplementations allow this option to be set.</dd><dt>SO_SNDLOWAT</dt><dd>Sets the minimum number of bytes to process for socket output operations. Non-blocking output operations shall process no dataif flow control does not allow the smaller of the send low water mark value or the entire request to be processed. This optiontakes an <b>int</b> value. Note that not all implementations allow this option to be set.</dd><dt>SO_SNDTIMEO</dt><dd>Sets the timeout value specifying the amount of time that an output function blocks because flow control prevents data frombeing sent. If a send operation has blocked for this time, it shall return with a partial count or with <i>errno</i> set to[EAGAIN] or [EWOULDBLOCK] if no data is sent. The default for this option is zero, which indicates that a send operation shall nottime out. This option stores a <b>timeval</b> structure. Note that not all implementations allow this option to be set.</dd></dl><p>For Boolean options, 0 indicates that the option is disabled and 1 indicates that the option is enabled.</p><p>Options at other protocol levels vary in format and name.</p></blockquote><h4><a name="tag_03_668_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>setsockopt</i>() shall return 0. Otherwise, -1 shall be returned and <i>errno</i> set to indicatethe error.</p></blockquote><h4><a name="tag_03_668_05"></a>ERRORS</h4><blockquote><p>The <i>setsockopt</i>() function shall fail if:</p><dl compact><dt>[EBADF]</dt><dd>The <i>socket</i> argument is not a valid file descriptor.</dd><dt>[EDOM]</dt><dd>The send and receive timeout values are too big to fit into the timeout fields in the socket structure.</dd><dt>[EINVAL]</dt><dd>The specified option is invalid at the specified socket level or the socket has been shut down.</dd><dt>[EISCONN]</dt><dd>The socket is already connected, and a specified option cannot be set while the socket is connected.</dd><dt>[ENOPROTOOPT]</dt><dd><br>The option is not supported by the protocol.</dd><dt>[ENOTSOCK]</dt><dd>The <i>socket</i> argument does not refer to a socket.</dd></dl><p>The <i>setsockopt</i>() function may fail if:</p><dl compact><dt>[ENOMEM]</dt><dd>There was insufficient memory available for the operation to complete.</dd><dt>[ENOBUFS]</dt><dd>Insufficient resources are available in the system to complete the call.</dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_668_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_668_07"></a>APPLICATION USAGE</h4><blockquote><p>The <i>setsockopt</i>() function provides an application program with the means to control socket behavior. An applicationprogram can use <i>setsockopt</i>() to allocate buffer space, control timeouts, or permit socket data broadcasts. The <a href="../basedefs/sys/socket.h.html"><i><sys/socket.h></i></a> header defines the socket-level options available to<i>setsockopt</i>().</p><p>Options may exist at multiple protocol levels. The SO_ options are always present at the uppermost socket level.</p></blockquote><h4><a name="tag_03_668_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_668_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_668_10"></a>SEE ALSO</h4><blockquote><p><a href="xsh_chap02_10.html#tag_02_10"><i>Sockets</i></a> , <a href="bind.html"><i>bind</i>()</a> , <a href="endprotoent.html"><i>endprotoent</i>()</a> , <a href="getsockopt.html"><i>getsockopt</i>()</a> , <a href="socket.html"><i>socket</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/netinet/in.h.html"><i><netinet/in.h></i></a>, <a href="../basedefs/sys/socket.h.html"><i><sys/socket.h></i></a></p></blockquote><h4><a name="tag_03_668_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 6. Derived from the XNS, Issue 5.2 specification.</p></blockquote><div class="box"><em>End of informative text.</em></div><hr><hr size="2" noshade><center><font size="2"><!--footer start-->UNIX ® is a registered Trademark of The Open Group.<br>POSIX ® is a registered Trademark of The IEEE.<br>[ <a href="../mindex.html">Main Index</a> | <a href="../basedefs/contents.html">XBD</a> | <a href="../utilities/contents.html">XCU</a> | <a href="../functions/contents.html">XSH</a> | <a href="../xrat/contents.html">XRAT</a>]</font></center><!--footer end--><hr size="2" noshade></body></html>⌨️ 快捷键说明
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