Append appId to the request payload

src/Dashboard/Http/Controllers/SendMessage.php

@@ -45,6 +45,9 @@ class SendMessage
                 $request->appId
             );
         } else {
+            // Add 'appId' to the payload.
+            $payload['appId'] = $request->appId;
+
             $channelManager->broadcastAcrossServers(
                 $request->appId, $request->channel, (object) $payload
             );