如何知道我们是否收到过DatagramPacket的东西？

Question

I'm implementing a client-server program, and wanted that my client, after waiting 5 seconds without an ACK-Answer from server, sends back the same packet...

I made it like this, so please tell me if it's okay..

dp = new DatagramPacket(packet , packet.length , host , port);
        sock.send(dp);
        time = System.currentTimeMillis();
        while ((System.currentTimeMillis() - time < 5000) && ack_dp.getLength() == 0) {
            sock.receive(ack_dp);
        }

        if (ack_dp.getLength() == 0)
            sock.send(dp);

so my program will wait 5 second of the ACK, if he doesnt receive anything, he will resend the same packet. I check if he received an ack or not with the packet length.. if it stays 0, then he hasnt received anything.. if it will be longer than 0, then out of the while-sequence and send a new packet.. (ps: ack_dp is 2bytes)

Answer 1

receive() on the socket will by default block, so your loop doesn't make sense here (even if the socket was set to non-blocking, it's a Bad Idea ^TM to busy-wait in 99.99% of the cases).

Use setSoTimeout() , and catch SocketTimeoutException instead.