202 lines
4.7 KiB
HTML
202 lines
4.7 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of GETPEERNAME</TITLE>
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</HEAD><BODY>
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<H1>GETPEERNAME</H1>
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Section: Linux Programmer's Manual (2)<BR>Updated: 2017-09-15<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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getpeername - get name of connected peer socket
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>#include <<A HREF="file:///usr/include/sys/socket.h">sys/socket.h</A>></B>
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<P>
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<B>int getpeername(int </B><I>sockfd</I><B>, struct sockaddr *</B><I>addr</I><B>, socklen_t *</B><I>addrlen</I><B>);</B>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>getpeername</B>()
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returns the address of the peer connected to the socket
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<I>sockfd</I>,
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in the buffer pointed to by
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<I>addr</I>.
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The
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<I>addrlen</I>
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argument should be initialized to indicate the amount of space pointed to
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by
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<I>addr</I>.
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On return it contains the actual size of the name returned (in bytes).
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The name is truncated if the buffer provided is too small.
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<P>
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The returned address is truncated if the buffer provided is too small;
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in this case,
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<I>addrlen</I>
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will return a value greater than was supplied to the call.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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On success, zero is returned.
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On error, -1 is returned, and
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<I>errno</I>
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is set appropriately.
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<A NAME="lbAF"> </A>
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<H2>ERRORS</H2>
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<DL COMPACT>
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<DT id="1"><B>EBADF</B>
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<DD>
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The argument
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<I>sockfd</I>
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is not a valid file descriptor.
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<DT id="2"><B>EFAULT</B>
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<DD>
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The
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<I>addr</I>
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argument points to memory not in a valid part of the
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process address space.
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<DT id="3"><B>EINVAL</B>
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<DD>
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<I>addrlen</I>
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is invalid (e.g., is negative).
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<DT id="4"><B>ENOBUFS</B>
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<DD>
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Insufficient resources were available in the system
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to perform the operation.
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<DT id="5"><B>ENOTCONN</B>
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<DD>
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The socket is not connected.
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<DT id="6"><B>ENOTSOCK</B>
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<DD>
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The file descriptor
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<I>sockfd</I>
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does not refer to a socket.
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</DL>
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<A NAME="lbAG"> </A>
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<H2>CONFORMING TO</H2>
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POSIX.1-2001, POSIX.1-2008, SVr4, 4.4BSD
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(<B>getpeername</B>()
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first appeared in 4.2BSD).
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<A NAME="lbAH"> </A>
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<H2>NOTES</H2>
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For background on the
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<I>socklen_t</I>
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type, see
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<B><A HREF="/cgi-bin/man/man2html?2+accept">accept</A></B>(2).
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<P>
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For stream sockets, once a
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<B><A HREF="/cgi-bin/man/man2html?2+connect">connect</A></B>(2)
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has been performed, either socket can call
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<B>getpeername</B>()
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to obtain the address of the peer socket.
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On the other hand, datagram sockets are connectionless.
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Calling
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<B><A HREF="/cgi-bin/man/man2html?2+connect">connect</A></B>(2)
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on a datagram socket merely sets the peer address for outgoing
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datagrams sent with
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<B><A HREF="/cgi-bin/man/man2html?2+write">write</A></B>(2)
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or
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<B><A HREF="/cgi-bin/man/man2html?2+recv">recv</A></B>(2).
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The caller of
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<B><A HREF="/cgi-bin/man/man2html?2+connect">connect</A></B>(2)
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can use
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<B>getpeername</B>()
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to obtain the peer address that it earlier set for the socket.
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However, the peer socket is unaware of this information, and calling
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<B>getpeername</B>()
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on the peer socket will return no useful information (unless a
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<B><A HREF="/cgi-bin/man/man2html?2+connect">connect</A></B>(2)
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call was also executed on the peer).
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Note also that the receiver of a datagram can obtain
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the address of the sender when using
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<B><A HREF="/cgi-bin/man/man2html?2+recvfrom">recvfrom</A></B>(2).
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<A NAME="lbAI"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?2+accept">accept</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+bind">bind</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?2+getsockname">getsockname</A></B>(2),
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<B><A HREF="/cgi-bin/man/man2html?7+ip">ip</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+socket">socket</A></B>(7),
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<B><A HREF="/cgi-bin/man/man2html?7+unix">unix</A></B>(7)
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<A NAME="lbAJ"> </A>
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<H2>COLOPHON</H2>
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This page is part of release 5.05 of the Linux
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<I>man-pages</I>
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project.
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A description of the project,
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information about reporting bugs,
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and the latest version of this page,
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can be found at
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<A HREF="https://www.kernel.org/doc/man-pages/.">https://www.kernel.org/doc/man-pages/.</A>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="7"><A HREF="#lbAB">NAME</A><DD>
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<DT id="8"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="9"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="10"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DT id="11"><A HREF="#lbAF">ERRORS</A><DD>
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<DT id="12"><A HREF="#lbAG">CONFORMING TO</A><DD>
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<DT id="13"><A HREF="#lbAH">NOTES</A><DD>
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<DT id="14"><A HREF="#lbAI">SEE ALSO</A><DD>
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<DT id="15"><A HREF="#lbAJ">COLOPHON</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:32 GMT, March 31, 2021
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</BODY>
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</HTML>
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