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diff --git a/doc/s6-tcpserverd.html b/doc/s6-tcpserverd.html new file mode 100644 index 0000000..6600a7b --- /dev/null +++ b/doc/s6-tcpserverd.html @@ -0,0 +1,113 @@ +<html> + <head> + <meta name="viewport" content="width=device-width, initial-scale=1.0" /> + <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> + <meta http-equiv="Content-Language" content="en" /> + <title>s6-networking: the s6-tcpserverd program</title> + <meta name="Description" content="s6-networking: the s6-tcpserverd program" /> + <meta name="Keywords" content="s6-networking s6-tcpserverd tcpserver ucspi tcp server super-server ipv4 ipv6 TCP/IP" /> + <!-- <link rel="stylesheet" type="text/css" href="//skarnet.org/default.css" /> --> + </head> +<body> + +<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-tcpserverd</tt> program </h1> + +<p> +<tt>s6-tcpserverd</tt> is the serving part of the +<a href="s6-tcpserver.html">s6-tcpserver</a> super-server. +It assumes that its stdin is a bound and listening TCP/IP socket, +and it accepts connections from clients connecting to it, +spawning a program to handle each connection. +</p> + +<h2> Interface </h2> + +<pre> + s6-tcpserverd [ -1 ] [ -v <em>verbosity</em> ] [ -c <em>maxconn</em> ] [ -C <em>localmaxconn</em> ] <em>prog...</em> +</pre> + +<ul> + <li> s6-tcpserverd accepts connections from clients to an already +bound and listening TCP socket which is its standard input. </li> + <li> For every TCP connection to this socket, it +spawns a <em>prog...</em> child with stdin reading from the network +socket and stdout writing to it. </li> + <li> Depending on the verbosity level, it logs what it does to stderr. </li> + <li> It runs until killed by a signal. Depending on the received +signal, it may kill its children before exiting. </li> +</ul> + +<h2> Environment variables </h2> + +<p> + For each connection, an instance of <em>prog...</em> is spawned with +the following variables set: +</p> + +<ul> + <li> PROTO: always set to TCP </li> + <li> TCPLOCALIP: set to the server socket's address </li> + <li> TCPLOCALPORT: set to the server socket's port </li> + <li> TCPREMOTEIP: set to the client socket's address </li> + <li> TCPREMOTEPORT: set to the client socket's port </li> + <li> TCPCONNNUM: set to the number of connections originating from +the same IP address </li> +</ul> + +<h2> Options </h2> + +<ul> + <li> <tt>-1</tt> : write the local port, followed by newline, +to stdout, and close stdout, right before entering the client-accepting loop. +If stdout is suitably redirected, this can be used by monitoring +programs to check when the server is accepting connections. This can be +used with s6's <a href="//skarnet.org/software/s6/notifywhenup.html">readiness +notification mechanism</a> to make sure subsequent services do not start +before the server is ready. </li> + <li> <tt>-v <em>verbosity</em></tt> : be more or less verbose. +By default, <em>verbosity</em> is 1: print warning messages to stderr. +0 means only print fatal error messages ; 2 means print status and +connection information for every client. </li> + <li> <tt>-c <em>maxconn</em></tt> : accept at most +<em>maxconn</em> concurrent connections. Default is 40. It is +impossible to set it higher than 16384. </li> + <li> <tt>-C <em>localmaxconn</em></tt> : accept at most +<em>localmaxconn</em> connections from the same IP address. +Default is 40. It is impossible to set it higher than <em>maxconn</em>. </li> +</ul> + +<h2> Signals </h2> + +<ul> + <li> SIGTERM: exit. </li> + <li> SIGHUP: send a SIGTERM and a SIGCONT to all children. </li> + <li> SIGQUIT: send a SIGTERM and a SIGCONT to all children, then exit. </li> + <li> SIGABRT: send a SIGKILL to all children, then exit. </li> +</ul> + +<h2> Notes </h2> + +<ul> + <li> Unlike its ancestor +<a href="https://cr.yp.to/ucspi-tcp/tcpserver.html">tcpserver</a>, +s6-tcpserverd performs just the bare minimum: the point is to have a +small and very fast process to serve connections with the least +possible overhead. Features such as access control and DNS resolution +are provided via the <a href="s6-tcpserver-access.html">s6-tcpserver-access</a> +program. </li> + <li> s6-tcpserverd is meant to be execve'd into by a program that gets +the listening socket. That program is normally +<a href="s6-tcpserver-socketbinder.html">s6-tcpserver-socketbinder</a>, +which creates the socket itself; but it can be a different one if the +socket is to be retrieved by another means, for instance by fd-passing +from a fd-holding daemon (some people call this "socket activation"). </li> +</ul> + +</body> +</html> |