Listening to events

netty-socketio provides listeners to react to incoming events.

Built-in connection events

Connect

server.addConnectListener(client -> {
    log.info("Client connected: {}", client.getSessionId());
});

Called whenever a client connects.

Disconnect

server.addDisconnectListener(client -> {
    log.info("Client disconnected: {}", client.getSessionId());
});

Custom event listeners

To listen for custom named events:

server.addEventListener("chat", ChatMessage.class,
    (client, data, ackRequest) -> {
        log.info("Chat received: {}", data.getText());
});

• "chat": event name.

• ChatMessage.class: class representing the payload.

• (client, data, ack): handler callback.

If you don’t need typed payloads, use Object.class or a generic type.

Acknowledgements

You can handle acknowledgements if the client expects a response:

server.addEventListener("ask", Request.class, (client, req, ackSender) -> {
    ackSender.sendAckResponse(new Response("done"));
});

Socket.IO protocol supports ack callbacks on both sides.