Few updates:

limit usable chars in username at register
update stream name regex
make redirect on publish to user/stream/live instead leaving it with hash (makes possible to share direct stream link)

src/Controller/Events.php

@@ -8,6 +8,7 @@ use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
 use Symfony\Bundle\FrameworkBundle\Controller\Controller;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
  * Class Events
@@ -53,7 +54,7 @@ class Events extends Controller
             $manager->persist($stream);
             $manager->flush();
 
-            return new Response();
+            return new RedirectResponse('live');
         }
 
         return new Response('', 401);

src/Controller/Register.php

@@ -55,6 +55,10 @@ class Register extends Controller
 
         $data = $request->request->all();
 
+        if (empty($data['username']) || !$this->isValidString($data['username'])) {
+            return new JsonResponse(['message' => 'Name is empty or contains illegal chars. Please use A-Z, a-z, 0-9, .-_'], 500);
+        }
+
         if ($this->repository->findOneBy(['username' => $data['username']])) {
             return new JsonResponse(['message' => 'Username is already taken'], 500);
         }
@@ -89,4 +93,14 @@ class Register extends Controller
     {
         return XmlUtils::phpize($this->container->getParameter('registrationEnabled'));
     }
+
+    /**
+     * @param null|string $string
+     * @return false|int
+     * @author Soner Sayakci <shyim@posteo.de>
+     */
+    private function isValidString(?string $string)
+    {
+        return preg_match('/^[A-Z|a-z|0-9|.|\-|_]+$/m', $string);
+    }
 }

src/Controller/Streams.php

@@ -97,7 +97,7 @@ class Streams extends Controller
         }
 
         if (empty($requestBody['name']) || !$this->isValidString($requestBody['name'])) {
-            return new JsonResponse(['message' => 'Name is empty or contains illegal strings'], 500);
+            return new JsonResponse(['message' => 'Name is empty or contains illegal chars'], 500);
         }
 
         $stream->setUser($this->getUser());
@@ -317,6 +317,6 @@ class Streams extends Controller
      */
     private function isValidString(?string $string)
     {
-        return preg_match('/^[a-z|A-Z|a-z|A-Z|0-9|.|\-|_|\{|\}|\:|\/|=|&|?]+$/m', $string);
+        return preg_match('/^[A-Z|a-z|0-9|.|\-|_|\{|\}|\:|\/|=|&|?]+$/m', $string);
     }
 }