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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Unix domain socket</span></span>

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<p>A <b>Unix domain socket</b> (<b>UDS</b>), <b>local socket</b>, or <b>inter-process communication</b> (<b>IPC</b>) <b>socket</b> is a <a href="Communication_endpoint" title="Communication endpoint">communication endpoint</a> for <a href="Inter-process_communication" title="Inter-process communication">exchanging data between processes</a> executing in the same <a href="Unix" title="Unix">Unix</a> or <a href="Unix-like" title="Unix-like">Unix-like</a> operating system.

</p><p>The name <i>Unix domain socket</i> refers to the <code>domain</code> argument value <code>AF_UNIX</code> that is passed to the function that creates a socket <a href="System_resource" title="System resource">system resource</a>. The same communication domain is also selected by <code>AF_LOCAL</code>. <sup id="cite_ref-man-unix-sockets_1-0" class="reference"><a href="#cite_note-man-unix-sockets-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p><p>Valid <code>type</code> argument values for a UDS are:<sup id="cite_ref-man-unix-sockets_1-1" class="reference"><a href="#cite_note-man-unix-sockets-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

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<ul><li><code>SOCK_STREAM</code> (compare to <a href="Transmission_Control_Protocol" title="Transmission Control Protocol">TCP</a>) – for a stream-oriented socket</li>

<li><code>SOCK_DGRAM</code> (compare to <a href="User_Datagram_Protocol" title="User Datagram Protocol">UDP</a>) – for a datagram-oriented socket that preserves message boundaries (as on most UNIX implementations, UNIX domain datagram sockets are always reliable and don't reorder datagrams)</li>

<li><code>SOCK_SEQPACKET</code> (compare to <a href="SCTP" class="mw-redirect" title="SCTP">SCTP</a>) – for a sequenced-packet socket that is connection-oriented, preserves message boundaries, and delivers messages in the order that they were sent</li></ul>

<p>The UDS facility is a standard component of a <a href="POSIX" title="POSIX">POSIX</a> <a href="Operating_system" title="Operating system">operating system</a>.

</p><p>The <a href="API" title="API">API</a> for a UDS is similar to that of an <a href="Internet_socket" class="mw-redirect" title="Internet socket">Internet socket</a>, but rather than using an underlying network protocol, all communication occurs entirely within the operating system <a href="Kernel_(operating_system)" title="Kernel (operating system)">kernel</a>. A UDS may use the file system as its address <a href="Name_space" class="mw-redirect" title="Name space">name space</a>. Some operating systems, like <a href="Linux" title="Linux">Linux</a>, offer additional namespaces. Processes reference a UDS as a file system <a href="Inode" title="Inode">inode</a>, so two processes can communicate by opening the same socket.

</p><p>In addition to sending data, processes may send <a href="File_descriptor" title="File descriptor">file descriptors</a> across a UDS connection using the <code>sendmsg()</code> and <code>recvmsg()</code> system calls. This allows the sending processes to grant the receiving process access to a file descriptor for which the receiving process otherwise does not have access.<sup id="cite_ref-neohapsis_2-0" class="reference"><a href="#cite_note-neohapsis-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-linux-cmsg-man-page_3-0" class="reference"><a href="#cite_note-linux-cmsg-man-page-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> This can be used to implement a rudimentary form of <a href="Capability-based_security" title="Capability-based security">capability-based security</a>.<sup id="cite_ref-wheeler-secure-linux-howto_4-0" class="reference"><a href="#cite_note-wheeler-secure-linux-howto-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

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<ul><li><a href="Network_socket" title="Network socket">Network socket</a> – Software-based endpoint of network communications</li>

<li><a href="Berkeley_sockets" title="Berkeley sockets">Berkeley sockets</a> – Inter-process communication API</li>

<li><a href="Pipeline_(Unix)" title="Pipeline (Unix)">Pipeline (Unix)</a> – Mechanism for inter-process communication using message passing</li>

<li><a href="Netlink" title="Netlink">Netlink</a> – Linux kernel interface for inter-process communication between processes</li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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</style><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://man7.org/linux/man-pages/man7/unix.7.html">"Linux Programmer's Manual (unix - sockets for local interprocess communication)"</a>. 30 April 2018<span class="reference-accessdate">. Retrieved <span class="nowrap">22 February</span> 2019</span>.</cite></span>

</li>

<li id="cite_note-neohapsis-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-neohapsis_2-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20130518084034/http://archives.neohapsis.com/archives/postfix/2000-09/1476.html">"Archive of the "Postfix Discussions" mailing list"</a>. 30 September 2000. Archived from <a rel="nofollow" class="external text" href="http://archives.neohapsis.com/archives/postfix/2000-09/1476.html">the original</a> on 18 May 2013<span class="reference-accessdate">. Retrieved <span class="nowrap">29 September</span> 2014</span>.</cite></span>

</li>

<li id="cite_note-linux-cmsg-man-page-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-linux-cmsg-man-page_3-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://linux.die.net/man/3/cmsg">"Linux man page - cmsg(3): access ancillary data"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">9 October</span> 2018</span>.</cite></span>

</li>

<li id="cite_note-wheeler-secure-linux-howto-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-wheeler-secure-linux-howto_4-0">^</a></b></span> <span class="reference-text"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.dwheeler.com/secure-programs/Secure-Programs-HOWTO/sockets.html">""Secure Programming for Linux and Unix HOWTO", Section 3.4 "Sockets and Network Connections""</a>. <i>dwheeler.com</i>. David A. Wheeler. 22 August 2004<span class="reference-accessdate">. Retrieved <span class="nowrap">29 September</span> 2014</span>.</cite></span>

</li>

</ol></div></div>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><span class="neverexpand"><code><a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9799919799/functions/socket.html">socket</a></code></span> – System Interfaces Reference, <a href="Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 5 from <a href="The_Open_Group" title="The Open Group">The Open Group</a></li>

<li><span class="neverexpand"><code><a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9799919799/functions/socketpair.html">socketpair</a></code></span> – System Interfaces Reference, <a href="Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 5 from <a href="The_Open_Group" title="The Open Group">The Open Group</a></li>

<li><span class="neverexpand"><code><a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9799919799/functions/sendmsg.html">sendmsg</a></code></span> – System Interfaces Reference, <a href="Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 5 from <a href="The_Open_Group" title="The Open Group">The Open Group</a></li>

<li><span class="neverexpand"><code><a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9799919799/functions/recvmsg.html">recvmsg</a></code></span> – System Interfaces Reference, <a href="Single_Unix_Specification" class="mw-redirect" title="Single Unix Specification">The Single UNIX Specification</a>, Version 5 from <a href="The_Open_Group" title="The Open Group">The Open Group</a></li>

<li><span class="neverexpand"><code><a rel="nofollow" class="external text" href="https://manned.org/cmsg.3">cmsg(3)</a></code></span> – <a href="Linux" title="Linux">Linux</a> Programmer's <a href="Man_page" title="Man page">Manual</a> – Library Functions</li>

<li><a rel="nofollow" class="external text" href="https://untroubled.org/ucspi-unix/">ucspi-unix</a>, UNIX-domain socket client-server command-line tools</li>

<li><a rel="nofollow" class="external text" href="https://lists.freebsd.org/pipermail/freebsd-performance/2005-February/001143.html">Unix sockets vs Internet sockets</a></li>

<li><a rel="nofollow" class="external text" href="https://beej.us/guide/bgipc/html/multi/index.html">Unix Sockets - Beej's Guide to Unix IPC</a></li></ul>

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</style><div id="Inter-process_communication278" style="font-size:114%;margin:0 4em"><a href="Inter-process_communication" title="Inter-process communication">Inter-process communication</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="2"><div><a href="Data" title="Data">Data</a> exchange among <a href="Thread_(computing)" title="Thread (computing)">threads</a> in <a href="Computer_program" title="Computer program">computer programs</a></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Methods</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Mmap" title="Mmap">Memory-mapped file</a></li>

<li><a href="Message_passing" title="Message passing">Message passing</a></li>

<li><a href="Message_queue" title="Message queue">Message queue and mailbox</a></li>

<li><a href="Named_pipe" title="Named pipe">Named pipe</a></li>

<li><a href="Anonymous_pipe" title="Anonymous pipe">Anonymous pipe</a></li>

<li><a href="Semaphore_(programming)" title="Semaphore (programming)">Semaphore</a></li>

<li><a href="Shared_memory" title="Shared memory">Shared memory</a></li>

<li><a href="Signal_(IPC)" title="Signal (IPC)">Signal</a></li>

<li>Sockets

<ul><li><a href="Network_socket" title="Network socket">Network</a></li>

</ul></li></ul>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Communication_protocol" title="Communication protocol">Protocols</a><br>and <a href="Technical_standard" title="Technical standard">standards</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<ul><li><a href="Apple_event" title="Apple event">Apple events</a></li>

<li><a href="Common_Object_Request_Broker_Architecture" title="Common Object Request Broker Architecture">CORBA</a></li>

<li><a href="OpenBinder" title="OpenBinder">OpenBinder</a></li>

<li><a href="POSIX" title="POSIX">POSIX</a> (various methods)</li>

<li><a href="Apache_Thrift" title="Apache Thrift">Thrift</a></li>

</div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="Library_(computing)" title="Library (computing)">Software libraries</a><br>and <a href="Software_framework" title="Software framework">frameworks</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em">

<li><a href="Libevent" title="Libevent">libevent</a></li>

<li><a href="SIMPL" title="SIMPL">SIMPL</a></li>

</div></td></tr></tbody></table></div>

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This article is issued from <a class="external text" title="Last edited on 2025-07-17" href="https://en.wikipedia.org/wiki/?title=Unix_domain_socket&oldid=1300977540">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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