Questions about Socket's sendPacket and flush implementation

[Piasy]

Hi, I've been working on porting Java implementation of EngineIO and SocketIO to Kotlin Multiplatform recently.

During the development and test process, I have a question about Socket's sendPacket and flush implementation:

https://github.com/socketio/engine.io-client-java/blob/main/src/main/java/io/socket/engineio/client/Socket.java#L696C1-L712C6

    private void sendPacket(Packet packet, final Runnable fn) {
        if (ReadyState.CLOSING == this.readyState || ReadyState.CLOSED == this.readyState) {
            return;
        }

        this.emit(EVENT_PACKET_CREATE, packet);
        this.writeBuffer.offer(packet);
        if (null != fn) {
            this.once(EVENT_FLUSH, new Listener() {
                @Override
                public void call(Object... args) {
                    fn.run();
                }
            });
        }
        this.flush();
    }

https://github.com/socketio/engine.io-client-java/blob/main/src/main/java/io/socket/engineio/client/Socket.java#L617C1-L627C6

    private void flush() {
        if (this.readyState != ReadyState.CLOSED && this.transport.writable &&
                !this.upgrading && this.writeBuffer.size() != 0) {
            if (logger.isLoggable(Level.FINE)) {
                logger.fine(String.format("flushing %d packets in socket", this.writeBuffer.size()));
            }
            this.prevBufferLen = this.writeBuffer.size();
            this.transport.send(this.writeBuffer.toArray(new Packet[this.writeBuffer.size()]));
            this.emit(EVENT_FLUSH);
        }
    }

When we want to send a packet, we add it to writeBuffer and trigger flush, and we send all packets in writeBuffer to transport, and we remove this amount of packets from writeBuffer in onDrain.

But if we call send multiple times before onDrain is triggered, let's say 3 times, with pkt1, pkt2, pkt3, then we will call transport.send 3 times, with [pkt1], [pkt1, pkt2], and [pkt1, pkt2, pkt3], and that's definitely a wrong behavior.

Do I miss something to prevent this case from happening?