Finish implementing initial setup process

php/Ping.php

@@ -0,0 +1,31 @@
+<?php
+if(!defined("COMMON"))
+    require("Common.php");
+
+$js = getJsonizedInput();
+
+$psk = "";
+$allow=false;
+
+if(!defined("CLIENTPSK")) {
+    $allow=true;
+} else {
+
+    if($js['client'] == CLIENTPSK) {
+        // Authorized. Send the PSK value to the client
+        $allow=true;
+        $psk = PSK;
+    }else {
+        $allow=false;
+    }
+
+}
+
+$ret = array(
+    "type" => "S2CPong",
+    "authorized" => $allow,
+    "psk" => $psk
+);
+
+die(json_encode($ret));
+?>