Added possibility to extract the raw socket to loop externally (#9)

When multiplexing between different streams there is the need to use stream_select() on the raw sockets, and then run for a single time into the main loop of the library. This change allows an extending class to obtain the raw socket.

Author: thg2k

src/MQTTClient.php

@@ -57,9 +57,6 @@ class MQTTClient implements ClientContract
     /** @var string|null */
     private $caFile;
 
-    /** @var resource|null */
-    private $socket;
-
     /** @var float */
     private $lastPingAt;
 
@@ -75,6 +72,9 @@ class MQTTClient implements ClientContract
     /** @var bool */
     private $interrupted = false;
 
+    /** @var resource|null */
+    protected $socket;
+
     /**
      * Constructs a new MQTT client which subsequently supports publishing and subscribing.
      *