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Using socket_connect with a reliable timeout in PHP
<?php
/**
* I was having trouble with socket connections timing out reliably. Sometimes,
* my timeout would be reached. Other times, the connect would fail after three
* to six seconds. I finally figured out it had to do with trying to connect to
* a routable, non-localhost address. It seems the socket_connect call would
* not fail immediately for those connections. This function is what I finally
* ended up with that reliably connects to a working server, fails quickly for
* a server that has an address/port that is not reachable and will reach the
* timeout for routable addresses that are not up.
*
* Full Story: http://brian.moonspot.net/socket-connect-timeout
*
* Copyright (c) 2015, Brian Moon of DealNews.com, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
* * Neither the name of DealNews.com Inc. nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
/**
* Example:
*
* Assuming these hosts are valid for your setup, this example would produce
* something like this:
*
* Trying: Good host...
* resource(10) of type (Socket)
*
* Trying: Routable, but not up...
* Failed to connect to 10.1.2.30:4730. (timed out after 102.1051ms)
* NULL
*
* Trying: Up but not listening...
* Failed to connect to 127.0.0.1:7676. (111: Connection refused; after 0.051ms)
* NULL
*
* =====
*
* $timeout = 100;
*
* $hosts = array(
* array(
* "desc" => "Good host",
* "host" => "127.0.0.1",
* "port" => "4730"
* ),
* array(
* "desc" => "Routable, but not up",
* "host" => "10.1.2.30",
* "port" => "4730"
* ),
* array(
* "desc" => "Up but not listening",
* "host" => "127.0.0.1",
* "port" => "7676"
* ),
* );
*
* foreach($hosts as $host){
*
* echo "Trying: $host[desc]...\n";
*
* try{
* $socket = socket_connect_timeout($host["host"], $host["port"], $timeout);
* } catch(Exception $e){
* echo $e->getMessage()."\n";
* $socket = null;
* }
*
* var_dump($socket);
*
* echo "\n";
*
* }
*
*/
function socket_connect_timeout($host, $port, $timeout=100){
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
/**
* Set the send and receive timeouts super low so that socket_connect
* will return to us quickly. We then loop and check the real timeout
* and check the socket error to decide if its conected yet or not.
*/
$connect_timeval = array(
"sec"=>0,
"usec" => 100
);
socket_set_option(
$socket,
SOL_SOCKET,
SO_SNDTIMEO,
$connect_timeval
);
socket_set_option(
$socket,
SOL_SOCKET,
SO_RCVTIMEO,
$connect_timeval
);
$now = microtime(true);
/**
* Loop calling socket_connect. As long as the error is 115 (in progress)
* or 114 (already called) and our timeout has not been reached, keep
* trying.
*/
$err = null;
$socket_connected = false;
do{
socket_clear_error($socket);
$socket_connected = @socket_connect($socket, $host, $port);
$err = socket_last_error($socket);
$elapsed = (microtime(true) - $now) * 1000;
}
while (($err === 115 || $err === 114) && $elapsed < $timeout);
/**
* For some reason, socket_connect can return true even when it is
* not connected. Make sure it returned true the last error is zero
*/
$socket_connected = $socket_connected && $err === 0;
if($socket_connected){
/**
* Set keep alive on so the other side does not drop us
*/
socket_set_option($socket, SOL_SOCKET, SO_KEEPALIVE, 1);
/**
* set the real send/receive timeouts here now that we are connected
*/
$timeval = array(
"sec" => 0,
"usec" => 0
);
if($timeout >= 1000){
$ts_seconds = $timeout / 1000;
$timeval["sec"] = floor($ts_seconds);
$timeval["usec"] = ($ts_seconds - $timeval["sec"]) * 1000000;
} else {
$timeval["usec"] = $timeout * 1000;
}
socket_set_option(
$socket,
SOL_SOCKET,
SO_SNDTIMEO,
$timeval
);
socket_set_option(
$socket,
SOL_SOCKET,
SO_RCVTIMEO,
$timeval
);
} else {
$elapsed = round($elapsed, 4);
if(!is_null($err) && $err !== 0 && $err !== 114 && $err !== 115){
$message = "Failed to connect to $host:$port. ($err: ".socket_strerror($err)."; after {$elapsed}ms)";
} else {
$message = "Failed to connect to $host:$port. (timed out after {$elapsed}ms)";
}
throw new Exception($message);
}
return $socket;
}

Where does the variable $tv_sec on line 169 come from? It seems like it's not being declared anywhere. Also on lines 168, 169 and 171, the array $timeval is spelt incorrectly as $timval.

Thanks for making this code public.

Owner

brianlmoon commented Apr 3, 2015

@rotexdegba thanks for pointing those out. I extracted this from a lib to make it something I could share and messed up some variables. I will get them fixed.

Owner

brianlmoon commented Apr 7, 2015

Updated the script with typos fixed. I never have a timeout over 1000ms, so I did not hit that part of the if. Sorry about that.

Hey I tried implementing this code, set the $timeout to 100 and this is what I get back
Failed to connect to xx.xx.xx. (60: Operation timed out; after 75069.3259ms)

Running on PHP Version 5.6.8

Also checked some of the PHP config values and the default_socket_timeout is even set to 60 so I'm not sure how it's staying alive for 75 seconds anyways? Any advice?

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