Close buffer when end() is called and last message is sent

Author: clue

Datagram/Buffer.php

@@ -55,6 +55,10 @@ public function handleWrite()
         if (!$this->outgoing) {
             $this->loop->removeWriteStream($this->socket);
             $this->listening = false;
+
+            if (!$this->writable) {
+                $this->close();
+            }
         }
     }