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hw2: completed but untested

This commit is contained in:
Claudio Maggioni 2020-05-07 17:08:12 +02:00
parent acc8707c3f
commit ea830e85bd
2 changed files with 69 additions and 5 deletions
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65
hw2/src/GBNTReceiver.java
View File

@ -2,13 +2,72 @@ import transport.Receiver;
import transport.TimeoutAction;
public class GBNTReceiver extends Receiver implements TimeoutAction {
private char sequence;
boolean firstPacket = true;
private static final int RECEIVER_TIMEOUT_MS = 1000;
private State state = State.SETUP;
enum State {
SETUP,
RECEIVING
}
private static byte[] generateACK(char sequence) {
byte[] dest = new byte[2];
dest[0] = (byte) ((sequence >> 8) & 0xFF);
dest[1] = (byte) (sequence & 0xFF);
return dest;
}
private static char readBigEndianChar(byte[] src, int offset) {
return (char) (src[offset] << 8 + src[offset + 1]);
}
private static char incrementAndRollover(char c) {
return (char) ((c + 1) % 65536);
}
@Override
public void timeoutAction() {
try {
disconnect();
} catch (java.lang.InterruptedException ex) {
System.out.println("Thread interrupted. Exiting directly.");
System.exit(0);
}
}
@Override
protected void unreliableReceive(byte[] bytes, int i, int i1) {
protected void unreliableReceive(byte[] bytes, int offset, int length) {
switch(this.state) {
case SETUP:
if (length != 2) {
if (firstPacket) return;
else {
state = State.RECEIVING;
this.unreliableReceive(bytes, offset, length);
}
}
sequence = readBigEndianChar(bytes, 0);
unreliableSend(bytes, offset, 2);
firstPacket = false;
break;
case RECEIVING:
if (length == 2) { // if packet is a close packet
if (incrementAndRollover(this.sequence) != readBigEndianChar(bytes, offset)) return; // ignore if not synchronized
this.unreliableSend(bytes, offset, 2);
timeoutAction();
}
if (length < 3) return;
char seq = readBigEndianChar(bytes, 0);
if (seq != incrementAndRollover(sequence)) return; //drop the packet
else {
this.unreliableReceive(bytes, offset + 2, length);
sequence = incrementAndRollover(sequence);
this.unreliableSend(generateACK(sequence), 0, 2);
}
break;
}
}
}

9
hw2/src/GBNTSender.java
View File

@ -13,6 +13,10 @@ public class GBNTSender extends transport.Sender implements TimeoutAction {
return (char) (src[offset] << 8 + src[offset + 1]);
}
private static char addAndRollover(char c, char i) {
return (char) ((c + i) % 65536);
}
private static char incrementAndRollover(char c) {
return (char) ((c + 1) % 65536);
}
@ -57,7 +61,7 @@ public class GBNTSender extends transport.Sender implements TimeoutAction {
private static final char W = 10;
private char base = (char) (new Random().nextInt() % 65536);
private char waitingACK = 0;
private int timeoutMs = 1000;
private int timeoutMs = 500;
private double rttEWMA = 0;
private double devRttEWMA = 0;
@ -107,7 +111,7 @@ public class GBNTSender extends transport.Sender implements TimeoutAction {
protected int reliableSend(byte[] bytes, int offset, int length) {
if (state != State.SENDING) throw new IllegalStateException();
Packet p = new Packet(base, bytes, offset, length);
Packet p = new Packet(addAndRollover(base, waitingACK), bytes, offset, length);
waitingACK++;
packets.add(p);
p.send();
@ -142,6 +146,7 @@ public class GBNTSender extends transport.Sender implements TimeoutAction {
byte[] expected = createSetupPacket();
if (bytes[offset] == expected[0] && bytes[1] == expected[offset + 1]) {
state = State.SENDING;
base = incrementAndRollover(base);
resumeSender();
} else {
sendSetup();