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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>accept</title></head><body bgcolor="white"><script type="text/javascript" language="JavaScript" src="../jscript/codes.js"></script><basefont size="3"> <a name="accept"></a> <a name="tag_03_09"></a><!-- accept --> <!--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_09_01"></a>NAME</h4><blockquote>accept - accept a new connection on a socket</blockquote><h4><a name="tag_03_09_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 accept(int</tt> <i>socket</i><tt>, struct sockaddr *restrict</tt> <i>address</i><tt>,<br> socklen_t *restrict</tt> <i>address_len</i><tt>);<br></tt></code></p></blockquote><h4><a name="tag_03_09_03"></a>DESCRIPTION</h4><blockquote><p>The <i>accept</i>() function shall extract the first connection on the queue of pending connections, create a new socket withthe same socket type protocol and address family as the specified socket, and allocate a new file descriptor for that socket.</p><p>The <i>accept</i>() function takes the following arguments:</p><dl compact><dt><i>socket</i></dt><dd>Specifies a socket that was created with <a href="../functions/socket.html"><i>socket</i>()</a>, has been bound to an addresswith <a href="../functions/bind.html"><i>bind</i>()</a>, and has issued a successful call to <a href="../functions/listen.html"><i>listen</i>()</a>.</dd><dt><i>address</i></dt><dd>Either a null pointer, or a pointer to a <b>sockaddr</b> structure where the address of the connecting socket shall bereturned.</dd><dt><i>address_len</i></dt><dd>Points to a <b>socklen_t</b> structure which on input specifies the length of the supplied <b>sockaddr</b> structure, and onoutput specifies the length of the stored address.</dd></dl><p>If <i>address</i> is not a null pointer, the address of the peer for the accepted connection shall be stored in the<b>sockaddr</b> structure pointed to by <i>address</i>, and the length of this address shall be stored in the object pointed to by<i>address_len</i>.</p><p>If the actual length of the address is greater than the length of the supplied <b>sockaddr</b> structure, the stored addressshall be truncated.</p><p>If the protocol permits connections by unbound clients, and the peer is not bound, then the value stored in the object pointedto by <i>address</i> is unspecified.</p><p>If the listen queue is empty of connection requests and O_NONBLOCK is not set on the file descriptor for the socket,<i>accept</i>() shall block until a connection is present. If the <a href="../functions/listen.html"><i>listen</i>()</a> queue isempty of connection requests and O_NONBLOCK is set on the file descriptor for the socket, <i>accept</i>() shall fail and set<i>errno</i> to [EAGAIN] or [EWOULDBLOCK].</p><p>The accepted socket cannot itself accept more connections. The original socket remains open and can accept more connections.</p></blockquote><h4><a name="tag_03_09_04"></a>RETURN VALUE</h4><blockquote><p>Upon successful completion, <i>accept</i>() shall return the non-negative file descriptor of the accepted socket. Otherwise, -1shall be returned and <i>errno</i> set to indicate the error.</p></blockquote><h4><a name="tag_03_09_05"></a>ERRORS</h4><blockquote><p>The <i>accept</i>() function shall fail if:</p><dl compact><dt>[EAGAIN] or [EWOULDBLOCK]</dt><dd><br>O_NONBLOCK is set for the socket file descriptor and no connections are present to be accepted.</dd><dt>[EBADF]</dt><dd>The <i>socket</i> argument is not a valid file descriptor.</dd><dt>[ECONNABORTED]</dt><dd><br>A connection has been aborted.</dd><dt>[EINTR]</dt><dd>The <i>accept</i>() function was interrupted by a signal that was caught before a valid connection arrived.</dd><dt>[EINVAL]</dt><dd>The <i>socket</i> is not accepting connections.</dd><dt>[EMFILE]</dt><dd>{OPEN_MAX} file descriptors are currently open in the calling process.</dd><dt>[ENFILE]</dt><dd>The maximum number of file descriptors in the system are already open.</dd><dt>[ENOTSOCK]</dt><dd>The <i>socket</i> argument does not refer to a socket.</dd><dt>[EOPNOTSUPP]</dt><dd>The socket type of the specified socket does not support accepting connections.</dd></dl><p>The <i>accept</i>() function may fail if:</p><dl compact><dt>[ENOBUFS]</dt><dd>No buffer space is available.</dd><dt>[ENOMEM]</dt><dd>There was insufficient memory available to complete the operation.</dd><dt>[EPROTO]</dt><dd><sup>[<a href="javascript:open_code('XSR')">XSR</a>]</sup> <img src="../images/opt-start.gif" alt="[Option Start]" border="0">A protocol error has occurred; for example, the STREAMS protocol stack has not been initialized. <img src="../images/opt-end.gif"alt="[Option End]" border="0"></dd></dl></blockquote><hr><div class="box"><em>The following sections are informative.</em></div><h4><a name="tag_03_09_06"></a>EXAMPLES</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_09_07"></a>APPLICATION USAGE</h4><blockquote><p>When a connection is available, <a href="../functions/select.html"><i>select</i>()</a> indicates that the file descriptor forthe socket is ready for reading.</p></blockquote><h4><a name="tag_03_09_08"></a>RATIONALE</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_09_09"></a>FUTURE DIRECTIONS</h4><blockquote><p>None.</p></blockquote><h4><a name="tag_03_09_10"></a>SEE ALSO</h4><blockquote><p><a href="bind.html"><i>bind</i>()</a> , <a href="connect.html"><i>connect</i>()</a> , <a href="listen.html"><i>listen</i>()</a>, <a href="socket.html"><i>socket</i>()</a> , the Base Definitions volume of IEEE Std 1003.1-2001, <a href="../basedefs/sys/socket.h.html"><i><sys/socket.h></i></a></p></blockquote><h4><a name="tag_03_09_11"></a>CHANGE HISTORY</h4><blockquote><p>First released in Issue 6. Derived from the XNS, Issue 5.2 specification.</p><p>The <b>restrict</b> keyword is added to the <i>accept</i>() prototype for alignment with the ISO/IEC 9899:1999standard.</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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