add ipv6 support

src/Server.php

@@ -115,7 +115,15 @@ class Server {
      */
     protected function openSocket(string $ip, int $port): bool
     {
-        $addr = "tcp://" . $ip . ':' . $port;
+        if (false !== filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6))
+        {
+            $addr = 'tcp://[' . $ip . ']:' . $port;
+        }
+
+        else
+        {
+            $addr = 'tcp://' . $ip . ':' . $port;
+        }
 
         $this->socket = stream_socket_server($addr, $errno, $errstr, STREAM_SERVER_BIND | STREAM_SERVER_LISTEN, $this->context);