Interrupting Events

[Tristan McHardie]

I am writing an application that provides reliable network transport over a deliberately unreliable socket (it is a university assignment). At this stage it is just a stop-and-wait protocol. I want to have two events that can trigger a resend:

* timeout event
* incorrectly numbered ack received

My question is, how do I start a timer and have either Unreliabe.receive() or a timeout event trigger a resend? Two events that cause one action.

[Rodrigo Alvarez]

Hi,

nc.util.Timer sounds appropriate for the timeout.

I suggest you start a "timeout thread" as soon as you start waiting (after you sent a packet, I guess), something like this:

    
long timeout=100;

Timer resendTimeoutTimer = new Timer();

TimerTask resendTask = new TimerTask() {
public void run() {
if (!canceled) {
// resend stuff here
}
}
};

resendTimeoutTimer.schedule(resendTask, timeout);

Then, you start waiting for the ACK. When it arrives, just set canceled to true and the thread you started will quietly do nothing when it will run().

Note: (make sure you have exactly one canceled variable per Thread you start and not a unique global one => maybe encapsulating it in the TimerTask or something)

[Tristan McHardie]

Hi, thanks for the help!

My next problem should probably be in the begginner forum, but I'll keep it in this thread as it's directly related to it.

The send() method below is an overriding method, which adds TCP-like reliability to a UDP socket. After the headers have been added, I need to call super.send() to pass the reliable packet to the unreliable socket.

My question is, how do I call super.send() from within the TimerTask, which is obviously a subclass?

Thanks,
Tristan

public void send(DatagramPacket applicationPacket) throws IOException {
        DatagramPacket transportPacket = new DatagramPacket(...)
        Timer resendTimer = new Timer();
        TimerTask resendTask;
        
        resendTask = new TimerTask() {
            public void run() {
                [B]//would like to call super.send(transportPacket); here[/B]
            }
        };
        
        resendTimer.schedule(resendTask, 0, RESEND_TIMEOUT);
    }

[Ernest Friedman-Hill]

I believe "OuterClassName.super.send()" will work.