Use system default DNS server config

Author: clue

README.md

@@ -918,10 +918,12 @@ also shares all of their features and implementation details.
 If you want to typehint in your higher-level protocol implementation, you SHOULD
 use the generic [`ConnectorInterface`](#connectorinterface) instead.
 
-In particular, the `Connector` class uses Google's public DNS server `8.8.8.8`
-to resolve all public hostnames into underlying IP addresses by default.
-If you want to use a custom DNS server (such as a local DNS relay or a company
-wide DNS server), you can set up the `Connector` like this:
+The `Connector` class will try to detect your system DNS settings (and uses
+Google's public DNS server `8.8.8.8` as a fallback if unable to determine your
+system settings) to resolve all public hostnames into underlying IP addresses by
+default.
+If you explicitly want to use a custom DNS server (such as a local DNS relay or
+a company wide DNS server), you can set up the `Connector` like this:
 
 ```php
 $connector = new Connector($loop, array(

composer.json

@@ -6,7 +6,7 @@
     "require": {
         "php": ">=5.3.0",
         "evenement/evenement": "^3.0 || ^2.0 || ^1.0",
-        "react/dns": "^0.4.11",
+        "react/dns": "^0.4.13",
         "react/event-loop": "^1.0 || ^0.5 || ^0.4 || ^0.3.5",
         "react/stream": "^1.0 || ^0.7.1",
         "react/promise": "^2.1 || ^1.2",

src/Connector.php

@@ -2,6 +2,7 @@
 
 namespace React\Socket;
 
+use React\Dns\Config\Config;
 use React\Dns\Resolver\Factory;
 use React\Dns\Resolver\Resolver;
 use React\EventLoop\LoopInterface;
@@ -56,9 +57,17 @@ public function __construct(LoopInterface $loop, array $options = array())
             if ($options['dns'] instanceof Resolver) {
                 $resolver = $options['dns'];
             } else {
+                if ($options['dns'] !== true) {
+                    $server = $options['dns'];
+                } else {
+                    // try to load nameservers from system config or default to Google's public DNS
+                    $config = Config::loadSystemConfigBlocking();
+                    $server = $config->nameservers ? reset($config->nameservers) : '8.8.8.8';
+                }
+
                 $factory = new Factory();
                 $resolver = $factory->create(
-                    $options['dns'] === true ? '8.8.8.8' : $options['dns'],
+                    $server,
                     $loop
                 );
             }