642 lines
17 KiB
HTML
642 lines
17 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<meta name="Copyright" content="Copyright (c) 2006 by IBM Corporation">
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<title>recvfrom()--Receive Data</title>
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<!-- Begin Header Records ========================================== -->
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<!-- Unix8 SCRIPT J converted by B2H R4.1 (346) (CMS) by V2KEA304 -->
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<!-- at RCHVMW2 on 17 Feb 1999 at 11:05:09 -->
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<!-- End Header Records -->
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<link rel="stylesheet" type="text/css" href="../rzahg/ic.css">
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</head>
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<body>
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<a name="Top_Of_Page"></a>
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<!-- Java sync-link -->
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<script type="text/javascript" language="Javascript" src="../rzahg/synch.js">
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</script>
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<h2>recvfrom()--Receive Data</h2>
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<div class="box" style="width: 60%;">
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<br>
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BSD 4.3 Syntax<br>
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<pre>
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#include <sys/types.h>
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#include <sys/socket.h>
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int recvfrom(int <em>socket_descriptor</em>,
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char *<em>buffer</em>,
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int <em>buffer_length</em>,
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int <em>flags</em>,
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struct sockaddr *<em>from_address</em>,
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int *<em>address_length</em>)
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</pre>
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<br>
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Service Program Name: QSOSRV1<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<br>
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<div class="box" style="width: 60%;">
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<br>
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<a href="_xopen_source.htm">UNIX 98 Compatible Syntax</a><br>
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<pre>
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#define _XOPEN_SOURCE 520
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#include <sys/socket.h>
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ssize_t recvfrom(int <em>socket_descriptor</em>,
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void *<em>buffer</em>,
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size_t <em>buffer_length</em>,
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int <em>flags</em>,
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struct sockaddr *<em>from_address</em>,
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socklen_t *<em>address_length</em>)
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</pre>
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<br>
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Service Program Name: QSOSRV1<br>
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<!-- iddvc RMBR -->
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<br>
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Default Public Authority: *USE<br>
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<!-- iddvc RMBR -->
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<br>
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Threadsafe: Yes<br>
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<!-- iddvc RMBR -->
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<br>
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</div>
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<p>The <em>recvfrom()</em> function is used to receive data through a connected
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or unconnected socket.</p>
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<p> There are two versions of
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the API, as shown above. The base i5/OS API uses BSD 4.3 structures and
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syntax. The other uses syntax and structures compatible with the UNIX 98
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programming interface specifications. You can select the UNIX 98 compatible
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interface with the <a href="_xopen_source.htm">_XOPEN_SOURCE</a> macro.</p>
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<br>
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<h3>Parameters</h3>
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<dl>
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<dt><strong>socket_descriptor</strong></dt>
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<dd>(Input) The socket descriptor that is to be read from.<br>
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<br>
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</dd>
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<dt><strong>buffer</strong></dt>
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<dd>(Input) The pointer to the buffer in which the data that is to be read is
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stored.<br>
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<br>
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</dd>
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<dt><strong>buffer_length</strong></dt>
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<dd>(Input) The length of the <em>buffer</em>.<br>
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<br>
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</dd>
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<dt>int <strong>flags</strong></dt>
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<dd>(Input) A flag value that controls the reception of the data. The
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<em>flags</em> value is either zero, or is obtained by performing an OR
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operation on one or more of the following constants:
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<table cellpadding="5">
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<!-- cols="15 85" -->
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<tr>
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<td align="left" valign="top"><em><samp>MSG_OOB</samp></em></td>
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<td align="left" valign="top">Receive out-of-band data. Valid only for sockets
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with an address family of <samp>AF_INET</samp> or <samp>AF_INET6</samp> and type <samp>SOCK_STREAM</samp>.</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em><samp>MSG_PEEK</samp></em></td>
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<td align="left" valign="top">Obtain a copy of the message without removing the
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message from the socket.</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em><samp>MSG_WAITALL</samp></em></td>
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<td align="left" valign="top">Wait for a full request or an error.</td>
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</tr>
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</table>
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<br>
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<br>
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</dd>
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<dt><strong>from_address</strong></dt>
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<dd>(Output) A pointer to a buffer of type <strong>struct sockaddr</strong>
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that contains the address from which the message was received.
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<p>The structure <strong>sockaddr</strong> is defined in
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<strong><sys/socket.h></strong>.</p>
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<p> The BSD 4.3 structure
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is:</p>
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<pre>
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struct sockaddr {
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u_short sa_family;
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char sa_data[14];
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};
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</pre>
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<p>The BSD 4.4/UNIX 98 compatible structure is:</p>
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<pre>
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typedef uchar sa_family_t;
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struct sockaddr {
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uint8_t sa_len;
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sa_family_t sa_family;
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char sa_data[14];
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};
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</pre>
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<p>The BSD 4.4 <em>sa_len</em> field is the length of the address. The <em>sa_family</em> field identifies
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the address family to which the address belongs, and <em>sa_data</em> is the
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address whose format is dependent on the address family.</p>
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<p> <strong>Note:</strong> See
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the usage notes about using different address families with
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<strong>sockaddr_storage</strong>.</p>
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<br>
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<br>
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</dd>
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<dt><strong>address_length</strong></dt>
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<dd>(Input/output) This parameter is a value-result field. The caller passes a
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pointer to the length of the <em>from_address</em> parameter. On return from
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the call, <em>address_length</em> will contain the actual length of the
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address.</dd>
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</dl>
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<br>
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<h3>Authorities</h3>
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<p>An <em>errno</em> of EACCES is returned when the socket pointed to by the
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<strong><em>socket_descriptor</em></strong> field is address family AF_INET and
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a nonblocking connect was attempted previously and was not successful. The
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nonblocking connect was not successful because the thread did not have
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authority to the associated APPC device. The thread performing the nonblocking
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connect must have retrieve, insert, delete, and update authority to the APPC
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device.</p>
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<br>
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<h3>Return Value</h3>
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<p><em>recvfrom()</em> returns an integer. Possible values are:</p>
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<ul>
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<li>-1 (unsuccessful)</li>
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<li>n (successful), where n is the number of bytes received.</li>
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</ul>
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<br>
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<h3>Error Conditions</h3>
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<p>When <em>recvfrom()</em> fails, <em>errno</em> can be set to one of the
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following:</p>
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<table cellpadding="5">
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<!-- cols="20 80" -->
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<tr>
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<td align="left" valign="top"><em>[EACCES]</em></td>
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<td align="left" valign="top">Permission denied.
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<p>The socket pointed to by the <em>socket_descriptor</em> parameter is using a
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connection-oriented transport service, and a <em>connect()</em> was previously
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completed. The process, however, does not have the appropriate privileges to
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the objects that were needed to establish a connection. For example, the
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<em>connect()</em> required the use of an APPC device that the process was not
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authorized to.</p>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EBADF]</em></td>
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<td align="left" valign="top">Descriptor not valid.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[ECONNABORTED]</em></td>
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<td align="left" valign="top">Connection ended abnormally.
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<p>This error code indicates that the transport provider ended the connection
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abnormally because of one of the following:</p>
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<ul>
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<li>The retransmission limit has been reached for data that was being sent on
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the socket.<br>
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<br>
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</li>
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<li>A protocol error was detected.<br>
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</li>
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</ul>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[ECONNREFUSED]</em></td>
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<td align="left" valign="top">The destination socket refused an attempted
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connect operation.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[ECONNRESET]</em></td>
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<td align="left" valign="top">A connection with a remote socket was reset by
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that socket.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EFAULT]</em></td>
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<td align="left" valign="top">Bad address.
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<p>The system detected an address which was not valid while attempting to
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access the <em>buffer</em>, <em>from_address</em>, or <em>address_length</em>
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parameter.</p>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EINTR]</em></td>
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<td align="left" valign="top">Interrupted function call.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EINVAL]</em></td>
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<td align="left" valign="top">Parameter not valid.
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<p>This error code indicates one of the following:</p>
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<ul>
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<li>The <em>buffer_length</em> parameter specifies a negative value.<br>
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<br>
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</li>
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<li>The <em>flags</em> parameter specifies a value that includes the
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<samp>MSG_OOB</samp> flag, but no OOB data was available to be received.<br>
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<br>
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</li>
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<li>The <em>flags</em> parameter specifies a value that includes the
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<samp>MSG_OOB</samp> flag, and the socket option <samp>SO_OOBINLINE</samp> has
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been set.<br>
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<br>
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</li>
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<li>The <em>socket_descriptor</em> parameter points to a socket that is using a
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connectionless transport service, is not a socket of type
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<samp>SOCK_RAW</samp>, and is not bound to an address.<br>
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</li>
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</ul>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EIO]</em></td>
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<td align="left" valign="top">Input/output error.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[ENOBUFS]</em></td>
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<td align="left" valign="top">There is not enough buffer space for the
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requested operation.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[ENOTCONN]</em></td>
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<td align="left" valign="top">Requested operation requires a connection.
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<p>This error code is returned only on sockets that use a connection-oriented
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transport service.</p>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[ENOTSOCK]</em></td>
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<td align="left" valign="top">The specified descriptor does not reference a
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socket.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EOPNOTSUPP]</em></td>
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<td align="left" valign="top">Operation not supported.
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<p>This error code indicates one of the following:</p>
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<ul>
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<li>The <em>flags</em> parameter specifies a value that includes the
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<samp>MSG_OOB</samp> flag, but the <em>socket_descriptor</em> parameter points
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to a connectionless socket.<br>
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<br>
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</li>
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<li>The <em>flags</em> parameter specifies a value that includes the
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<samp>MSG_OOB</samp> flag, but the <em>socket_descriptor</em> parameter points
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to a socket that does not have an address family of <samp>AF_INET</samp> or <samp>AF_INET6</samp>.<br>
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</li>
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</ul>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[ETIMEDOUT]</em></td>
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<td align="left" valign="top">A remote host did not respond within the timeout
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period.
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<p>A non-blocking <em>connect()</em> was previously issued that resulted in the
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connection establishment timing out. No connection is established. This error
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code is returned only on sockets that use a connection-oriented transport
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service.</p>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EUNATCH]</em></td>
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<td align="left" valign="top">The protocol required to support the specified
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address family is not available at this time.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EUNKNOWN]</em></td>
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<td align="left" valign="top">Unknown system state.<br>
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<br>
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</td>
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</tr>
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<tr>
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<td align="left" valign="top"><em>[EWOULDBLOCK]</em></td>
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<td align="left" valign="top">Operation would have caused the thread to be
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suspended.</td>
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</tr>
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</table>
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<br>
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<br>
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<h3>Error Messages</h3>
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<table width="100%" cellpadding="5">
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<!-- cols="15 85" -->
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<tr>
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<th align="left" valign="top">Message ID</th>
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<th align="left" valign="top">Error Message Text</th>
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</tr>
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<tr>
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<td width="15%" valign="top">CPE3418 E</td>
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<td width="85%" valign="top">Possible APAR condition or hardware failure.</td>
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</tr>
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<tr>
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<td align="left" valign="top">CPF9872 E</td>
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<td align="left" valign="top">Program or service program &1 in library
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&2 ended. Reason code &3.</td>
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</tr>
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<tr>
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<td align="left" valign="top">CPFA081 E</td>
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<td align="left" valign="top">Unable to set return value or error code.</td>
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</tr>
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</table>
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<br>
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<br>
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<h3>Usage Notes</h3>
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<ol>
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<li>For sockets that use a connection-oriented transport service (for example,
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sockets with a type of <samp>SOCK_STREAM</samp>), a returned value of zero
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indicates one of the following:
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<ul>
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<li>The partner program has issued a <em>close()</em> for the socket.<br>
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<br>
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</li>
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<li>The partner program has issued a <em>shutdown()</em> to disable writing to
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the socket.<br>
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<br>
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</li>
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<li>The connection is broken and the error was returned on a previously issued
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socket function.<br>
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<br>
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</li>
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<li>A <em>shutdown()</em> to disable reading was previously done on the
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socket.</li>
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</ul>
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<br>
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<br>
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</li>
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<li>If the socket is using a connection-oriented transport service, the
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<em>from_address</em> and <em>address_length</em> parameters are ignored.<br>
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<br>
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</li>
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<li>The following applies to sockets that use a connectionless transport
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service (for example, a socket with a type of <samp>SOCK_DGRAM</samp>):
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<ul>
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<li>If a <em>connect()</em> has been issued previously, then data can be
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received only from the address specified in the previous
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<em>connect()</em>.<br>
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<br>
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</li>
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<li>If the <em>from_address</em> parameter is set to NULL or
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<em>address_length</em> specifies a value of zero, the address from which data
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is received is discarded by the system.<br>
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<br>
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</li>
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<li>If the length of the address to be returned exceeds the length of the
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<em>from_address</em> parameter, the returned address is truncated.<br><br></li>
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<li>The structure
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<strong>sockaddr</strong> is a generic structure used for any address family
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but it is only 16 bytes long. The actual address returned for some address
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families may be much larger. You should declare storage for the address with
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the structure <strong>sockaddr_storage</strong>. This structure is large enough
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and aligned for any protocol-specific structure. It may then be cast as
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<strong>sockaddr</strong> structure for use on the APIs. The <em>ss_family</em>
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field of the <strong>sockaddr_storage</strong> will always align with the
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family field of any protocol-specific structure.
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<p>The BSD 4.3 structure is:</p>
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|
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<pre>
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#define _SS_MAXSIZE 304
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#define _SS_ALIGNSIZE (sizeof (char*))
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#define _SS_PAD1SIZE (_SS_ALIGNSIZE - sizeof(sa_family_t))
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#define _SS_PAD2SIZE (_SS_MAXSIZE - (sizeof(sa_family_t)+
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_SS_PAD1SIZE + _SS_ALIGNSIZE))
|
|
|
|
struct sockaddr_storage {
|
|
sa_family_t ss_family;
|
|
char _ss_pad1[_SS_PAD1SIZE];
|
|
char* _ss_align;
|
|
char _ss_pad2[_SS_PAD2SIZE];
|
|
};
|
|
</pre>
|
|
|
|
<p>The BSD 4.4/UNIX 98 compatible structure is:</p>
|
|
|
|
<pre>
|
|
#define _SS_MAXSIZE 304
|
|
#define _SS_ALIGNSIZE (sizeof (char*))
|
|
#define _SS_PAD1SIZE (_SS_ALIGNSIZE - (sizeof(uint8_t) + sizeof(sa_family_t)))
|
|
#define _SS_PAD2SIZE (_SS_MAXSIZE - (sizeof(uint8_t) + sizeof(sa_family_t)+
|
|
_SS_PAD1SIZE + _SS_ALIGNSIZE))
|
|
|
|
struct sockaddr_storage {
|
|
uint8_t ss_len;
|
|
sa_family_t ss_family;
|
|
char _ss_pad1[_SS_PAD1SIZE];
|
|
char* _ss_align;
|
|
char _ss_pad2[_SS_PAD2SIZE];
|
|
};
|
|
</pre>
|
|
|
|
<br>
|
|
</li>
|
|
|
|
<li>If the socket is using an address family of <samp>AF_UNIX</samp>, the
|
|
address (which is a path name) is returned in the default coded character set
|
|
identifier (CCSID) currently in effect for the job.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>If the socket is using an address family of <samp>AF_UNIX_CCSID</samp>, the
|
|
output structure sockaddr_unc defines the format and coded character set
|
|
identifier (CCSID) of the address (which is a path name).<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>The entire message must be read in a single read operation. If the size of
|
|
the message is too large to fit in the user supplied buffer, the remaining
|
|
bytes of the message are discarded.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>A returned value of zero indicates one of the following:
|
|
|
|
<ul>
|
|
<li>The partner program has sent a NULL message (a datagram with no user
|
|
data).<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>A <em>shutdown()</em> to disable reading was previously done on the
|
|
socket.<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li>The buffer length specified was zero.</li>
|
|
</ul>
|
|
</li>
|
|
</ul>
|
|
|
|
<br>
|
|
</li>
|
|
|
|
<li>When you develop in C-based
|
|
languages and an application is compiled with the _XOPEN_SOURCE macro defined
|
|
to the value 520 or greater, the <em>recvfrom()</em> API is mapped to
|
|
<em>qso_recvfrom98()</em>.</li>
|
|
</ol>
|
|
|
|
<br>
|
|
|
|
|
|
<h3>Related Information</h3>
|
|
|
|
<ul>
|
|
<li><a href=
|
|
"_xopen_source.htm">_XOPEN_SOURCE</a>--Using _XOPEN_SOURCE for the UNIX 98
|
|
compatible interface<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><a href="fcntl.htm">fcntl()</a>--Perform File Control Command<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><a href="ioctl.htm">ioctl()</a>--Perform I/O Control Request<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><a href="recv.htm">recv()</a>--Receive Data<br>
|
|
<br>
|
|
</li>
|
|
|
|
<li><a href="recvms.htm">recvmsg()</a>--Receive Data or Descriptors or
|
|
Both</li>
|
|
</ul>
|
|
|
|
<br>
|
|
<hr>
|
|
API introduced: V3R1
|
|
|
|
<hr>
|
|
<center>
|
|
<table cellpadding="2" cellspacing="2">
|
|
<tr align="center">
|
|
<td valign="middle" align="center"><a href="#Top_Of_Page">Top</a> |
|
|
<a href="unix.htm">UNIX-Type APIs</a> |
|
|
<a href="aplist.htm">APIs by category</a> </td>
|
|
</tr>
|
|
</table>
|
|
</center>
|
|
</body>
|
|
</html>
|
|
|