Clear socket.io buffer on disconnect/error

Question

1) In disconnected mode I am sending some data to server and on socket error I am displaying message "Please check your internet connection and try again".

2) When socket reconnect it is sending step 1 data to server (As per functionality it should be discarded).

I don't know close/disconnect clears buffer or not and I also want to reconnect automatically when connection is available. I am creating android app and using socket.io.

Answer 1

Here is a way out to perform it which worked for me, it may be a little tricky and yes the code here is a combination of several answers which I found on StackOverflow.

The trick I used is to close the socket, make it NULL and then recreate and try to connect it. It helps to clear the buffer and reconnect in a smooth way.

ackMessageTimeOut = new AckMessageTimeOut(5000) {
            @Override
            public void call(Object... args) {
                if (args != null) {
                    if (args[0].toString().equalsIgnoreCase("No Ack")) {
                        Log.d("ACK_SOCKET", "AckWithTimeOut : " + args[0].toString());
                        acknowledgeMessage(null);
                        if (socket != null) {
                            socket.close();
                            socket = null;
                            connectSocket(); // Custom method which creates the socket and tries to connect it.
                        }
                    } else if (args[0].toString().equalsIgnoreCase("true")) {
                        cancelTimer(); //cancel timer if emit ACK return true
                        Log.d("ACK_SOCKET", "AckWithTimeOut : " + args[0].toString());
                    }
                }
            }
        };

        socket.emit("sendMessage", message, ackMessageTimeOut); // You can apply it on whatever event you want.

AckMessageTimeOut class is as below:

private class AckMessageTimeOut implements Ack {

        private Timer timer;
        private long timeOut = 0;
        private boolean called = false;

        AckMessageTimeOut(long timeout_after) {
            if (timeout_after <= 0)
                return;
            this.timeOut = timeout_after;
            startTimer();
        }

        private void startTimer() {
            timer = new Timer();
            timer.schedule(new TimerTask() {
                @Override
                public void run() {
                    callback("No Ack");
                }
            }, timeOut);
        }

        private void resetTimer() {
            if (timer != null) {
                timer.cancel();
                startTimer();
            }
        }

        void cancelTimer() {
            if (timer != null)
                timer.cancel();
        }

        void callback(Object... args) {
            if (called)
                return;

            called = true;
            cancelTimer();
            call(args);
        }

        @Override
        public void call(Object... objects) {

        }
    }