While I was developing myself in Bwapp, messages with the hello type in the server-client section of push.services.mozilla in the WebSocketHistory section sent each other. What is the reason for this?

I don't understand that why it happened.
While I was developing myself in Bwapp, messages with the hello type in the server-client section of push.services.mozilla in the WebSocketHistory section sent each other. What is the reason for this?

I don't understand that why it happened.