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authorLaurent Bercot <ska-skaware@skarnet.org>2023-09-30 05:40:04 +0000
committerLaurent Bercot <ska@appnovation.com>2023-09-30 05:40:04 +0000
commitbef76b45f480aa41209efdec09fc6bb0bfde7cbe (patch)
treebb3945da0504c569ff325829bf5f895f8e355039 /doc/s6-tcpserver-socketbinder.html
parenta068a3256fab3b77b7d1bc9ce201c954a9b00c94 (diff)
downloads6-networking-bef76b45f480aa41209efdec09fc6bb0bfde7cbe.tar.xz
Great Tcpserver Unification. Prepare for 2.6.0.0.
Signed-off-by: Laurent Bercot <ska@appnovation.com>
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+ <title>s6-networking: the s6-tcpserver-socketbinder program</title>
+ <meta name="Description" content="s6-networking: the s6-tcpserver-socketbinder program" />
+ <meta name="Keywords" content="s6-networking s6-tcpserver-socketbinder tcpserver ucspi inet ipv4 ipv6 socket bind listen TCP/IP" />
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+<p>
+<a href="index.html">s6-networking</a><br />
+<a href="//skarnet.org/software/">Software</a><br />
+<a href="//skarnet.org/">skarnet.org</a>
+</p>
+
+<h1> The <tt>s6-tcpserver-socketbinder</tt> program </h1>
+
+<p>
+<tt>s6-tcpserver-socketbinder</tt> binds an INET domain
+socket to an IPv4 or IPv6 address and port, then executes a program.
+</p>
+
+<h2> Interface </h2>
+
+<pre>
+ s6-tcpserver-socketbinder [ -d | -D ] [ -b <em>backlog</em> ] [ -M | -m ] [ -B ] <em>ip</em> <em>port</em> <em>prog...</em>
+</pre>
+
+<ul>
+ <li> s6-tcpserver-socketbinder creates a TCP socket
+and binds it to IP address <em>ip</em>, port <em>port</em>.
+It prepares the socket to accept connections by calling
+<a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/listen.html">listen()</a>. </li>
+ <li> It then execs into <em>prog...</em> with the open socket
+as its standard input. </li>
+</ul>
+
+<h2> Options </h2>
+
+<ul>
+ <li> <tt>-d</tt>&nbsp;: allow instant rebinding to the same IP and port
+even if it has been used not long ago - this is the SO_REUSEADDR flag to
+<a href="https://pubs.opengroup.org/onlinepubs/9699919799/functions/setsockopt.html">setsockopt()</a>
+and is generally used with server programs. This is the default. </li>
+ <li> <tt>-D</tt>&nbsp;: disallow instant rebinding to the same path. </li>
+ <li> <tt>-b&nbsp;<em>backlog</em></tt>&nbsp;: set a maximum of
+<em>backlog</em> backlog connections on the socket - extra
+connection attempts will rejected by the kernel. The default is the maximum
+number allowed by the system. If <em>backlog</em>
+is 0, then the socket will be created, but it <strong>will not be
+listening</strong>. </li>
+ <li> <tt>-M</tt>&nbsp;: create a TCP socket. This is the default. </li>
+ <li> <tt>-m</tt>&nbsp;: create a UDP socket. Note
+that by default UDP sockets are not connection-mode, and <tt>listen()</tt>
+will fail - so you should always give the <tt>-b0</tt> option to
+s6-tcpserver-socketbinder along with <tt>-m</tt>. </li>
+ <li> <tt>-B</tt>&nbsp;: create a blocking socket. Default is non-blocking. </li>
+</ul>
+
+<h2> Notes </h2>
+
+<ul>
+ <li> The socket is provided <strong>non-blocking by default</strong>. </li>
+ <li> s6-tcpserver-socketbinder is part of a set of basic blocks used to
+build a flexible TCP/IP super-server. It normally should be given a
+command line crafted to make it execute into
+<a href="s6-tcpserverd.html">s6-tcpserverd</a> to accept connections
+from clients, or into a program such as
+<a href="//skarnet.org/software/s6/s6-applyuidgid.html">s6-applyuidgid</a>
+to drop privileges before doing so. </li>
+ <li> The <a href="s6-tcpserver.html">s6-tcpserver</a> program does
+exactly this. It implements
+a full TCP/IP super-server by building a command line starting with
+s6-tcpserver-socketbinder and ending with s6-tcpserverd followed by the
+application program, and executing into it. </li>
+ <li> For s6-tcpserver-socketbinder, <tt>::</tt> means "all IPv6 addresses",
+and <tt>0.0.0.0</tt> means "all IPv4 addresses". It does not provide a way
+to bind a socket to all addresses regardless of protocol; instead, you
+should use two sockets, one for IPv4 and one for IPv6. </li>
+</ul>
+
+</body>
+</html>