Wakanda websocket onclose not firing on network disconnect

Question

I have a websocket implementation on Wakanda Server. I am tracking connected browsers server side. When I reload the page, I get the onclose event of the websocket as expected.

I would have expected when I break a network connection that I would also have this event fire. Am I misunderstanding? Is there a way to have a function fire when a network connection is lost to a websocket client?

For reference, I am using Wakanda 10.

Answer 1

To help you understand the problem I will give you some details about websocket connections :

• It uses TCP
• If a remote client(browser for instance) closes a TCP connection gracefully the server is notified (FIN)
• If a remote client crashes, the OS running the client application notifies the server (RST)
• If a TCP connection is open between a server and a client the connection will be assumed open even if there is absolutely no exchange of data for a while unless keepalive is activated.
• The WebSocket spec adds a close message so the server/client can handle a graceful close
• The WebSocket spec adds a ping/pong message exchange but does not impose a timeout. From RFC : Upon receipt of a Ping frame, an endpoint MUST send a Pong frame in response, unless it already received a Close frame. It SHOULD respond with Pong frame as soon as is practical.
• In Wakanda's implementation of the RFC we respond to received ping messages but don't send our own ping messages

This can be a new feature where we can either :

• expose a ping method through the message port with a pong timeout
• add a websocket keepalive option with configurable timeout at the moment of adding the websocket handler.
• add a TCP keepalive option with configurable timeout at the moment of adding the websocket handler.

For the time being, you can send a message of your choice to the client side every N seconds and wait for a response with a timeout of T. If you don't receive a response you can assume the connexion is lost and close it.