private void RdtReceive(byte[] datagram)
{
bool isOk = rdt.IsOk(datagram);
string str = rdt.GetDatagramContentString(datagram);
bool isAck = rdt.IsAck(datagram);
bool isNack = rdt.IsNack(datagram); //Very naive implementation!
int seqDatagram = rdt.GetSeqNum(datagram);
/*We are sender*/
if (state == (int)STATE.WaitingForAck)
{
if (isOk && isAck && seqDatagram == senderSeq)
{
if (messageBuffer.Count > 0)
{
senderSeq = rdt.Incmod(senderSeq, flipBit); //toggle seq bit by using window of 2. 0->1 || 1->0
RaiseOnDeliver(InvokeReason.Debug, "Sending 1st queued message");
ToggleState();
RdtSend(messageBuffer[0]);
messageBuffer.RemoveAt(0);
}
else
{
ToggleState();
senderSeq = rdt.Incmod(senderSeq, flipBit); //toggle seq bit by using window of 2. 0->1 || 1->0
RaiseOnDeliver(InvokeReason.Debug, "Received correct ACK, switching states to #" + state.ToString());
}
}
else
{
RdtSend(previouslySentDatagram, true);
RaiseOnDeliver(InvokeReason.Debug, "Sender got received corrupted or out of order packet. Resending");
}
}
/*We are receiver*/
else
{
if (!isOk)
{
//Corrupt
RdtSend(rdt.MakeAck(receiverSeq, true), true);
RaiseOnDeliver(InvokeReason.Debug, "Received corrupted, sending NACK");
}
else if (isOk && receiverSeq != seqDatagram)
{
//Unexpected seqnum
RdtSend(rdt.MakeAck(rdt.Incmod(receiverSeq, flipBit)), true);
RaiseOnDeliver(InvokeReason.Debug, "Received out-of-order, sending ACK #"
+ receiverSeq.ToString());
}
else
{
//Received new message
RaiseOnDeliver(InvokeReason.Receiver, str);
receiverSeq = rdt.Incmod(receiverSeq, flipBit);
RdtSend(rdt.MakeAck(seqDatagram), true);
}
}
}
/*This implementation has flaw where gbnWindow doesn't mean window per se,
* more like whole seqnum space...Will do proper way with selective repeat.*/
public GoBackN(VirtualSocket socket)
{
rdt = new RdtUtils();
this.socket = socket;
socket.Start();
socket.OnReceive += RdtReceive;
gbnSendDictionary = new Dictionary <int, byte[]>();
gbnLatestAck = rdt.MakeAck(0);
}
private void RdtReceive(byte[] datagram)
{
bool isOk = rdt.IsOk(datagram);
string str = rdt.GetDatagramContentString(datagram);
bool isAck = rdt.IsAck(datagram);
int seqNum = rdt.GetSeqNum(datagram);
if (isOk)
{
if (isAck)
{
try
{
if (gbnBase != gbnNextSeqNum)
{
gbnSendDictionary.Remove(seqNum);
gbnBase = seqNum + 1;
gbnBase = gbnBase % gbnWindowSize;
//timer is running so stop/cancel
/*All standing packets are ack'd*/
if (gbnBase == gbnNextSeqNum)
{
OnDeliver?.Invoke(InvokeReason.Debug, "Has sent all pending messages successfully" + PrintGbnDebug());
if (cts != null)
{
cts.Cancel();
}
}
else
{
OnDeliver?.Invoke(InvokeReason.Debug, "2" + PrintGbnDebug());
//start new timer
/*CancellationTokenSource aCTS = new CancellationTokenSource();
* cts = aCTS;
* await Timertimeout(aCTS.Token);
* if (cts == aCTS)
* {
* cts = null;
* }*/
}
}
}
catch (OperationCanceledException) { }
}
else
{
/*not ack, not corrupt*/
if (seqNum == gbnExpectedSeqNum)
{
gbnLatestAck = rdt.MakeAck(gbnExpectedSeqNum);
RdtSend(gbnLatestAck, true);
gbnExpectedSeqNum++;
gbnExpectedSeqNum = gbnExpectedSeqNum % gbnWindowSize;
//If there is a subscriber attached to OnDeliver (e.g. UI), invoke event.
OnDeliver?.Invoke(InvokeReason.Receiver, str);
OnDeliver?.Invoke(InvokeReason.Debug, "3" + PrintGbnDebug());
}
else
{
/*As in not waiting for any acks, ie is receiver*/
if (gbnSendDictionary.Count == 0)
{
OnDeliver?.Invoke(InvokeReason.Debug, "Unexpected ACK SEQ (lost packets or duplicates?), resending ACK for datagram: "
+ rdt.GetSeqNum(gbnLatestAck).ToString());
RdtSend(gbnLatestAck, true);
}
}
}
}
else
{
/*corrupt
* Assuming we are receiver e.g. no outstanding acks
*/
if (gbnSendDictionary.Count == 0)
{
OnDeliver?.Invoke(InvokeReason.Debug, "Corrupted datagram. Resending ACK with seq: "
+ rdt.GetSeqNum(gbnLatestAck).ToString());
RdtSend(gbnLatestAck, true);
}
}
}
private void RdtReceive(byte[] datagram)
{
bool isOk = rdt.IsOk(datagram);
if (isOk)
{
string str = rdt.GetDatagramContentString(datagram);
bool isAck = rdt.IsAck(datagram);
byte seqNum = (byte)rdt.GetSeqNum(datagram);
if (isAck)
{
//Mark as ack'd
//If seq == sendBase => move window by:
//Go through buffer and if packets are in window and pkt.sent = false => send it and toggle bool
if (rdt.IsSeqInRange(seqNum, srSendBase, (byte)(srSendBase + srWindowSize - 1)))
{
sendBucket.MarkAsAcked(seqNum);
OnDeliver?.Invoke(InvokeReason.Debug, "Received ACK: " + seqNum.ToString()
+ PrintSRDebugInfo());
if (seqNum == srSendBase)
{
//int i = 0;
//While packet is sent -> remove it from sendBucket, increment counter, add counter to srSendBase
while (sendBucket.IsSent(srSendBase) && sendBucket.IsAcked(srSendBase))
{
sendBucket.RemoveFromBucket(srSendBase);
srSendBase++;
}
//While packet in sendBucket is in new window && hasn't been sent, send it and toggle it's state
//E.g for each srSendBase to srSendBase + N -1, if is in sendBucket & is not sent, send it now
//As dictionary is not ordered, we loop over range srSendBase -> srSendBase + N - 1. Stopping early if key isn't in bucket.
for (byte i = srSendBase; rdt.IsSeqInRange(i, srSendBase, (byte)(srSendBase + srWindowSize - 1)); i++)
{
if (!sendBucket.ContainsKey(i))
{
break;
}
socket.Send(sendBucket.GetDatagramBySeq(i));
sendBucket.MarkAsSent(i);
//srNextSeqNum++;
}
OnDeliver.Invoke(InvokeReason.Debug, "Sender window moved. " + PrintSRDebugInfo());
}
}
}
else
{
if (rdt.IsSeqInRange(seqNum, (byte)(srRcvBase - srWindowSize), (byte)(srRcvBase + srWindowSize - 1)))
{
RdtSend(rdt.MakeAck(seqNum), true);
OnDeliver?.Invoke(InvokeReason.Debug, "Received Pkt: " + seqNum.ToString()
+ PrintSRDebugInfo());
if (rdt.IsSeqInRange(seqNum, srRcvBase, (byte)(srRcvBase + srWindowSize - 1)))
{
if (!rcvBucket.ContainsKey(seqNum))
{
rcvBucket.AddToBucket(datagram, seqNum);
}
else
{
OnDeliver.Invoke(InvokeReason.Debug, "Received duplicate: " + seqNum.ToString());
}
if (seqNum == srRcvBase)
{
/*Pass a Action delegate for handling method. Method chain removes from buffer,
* handles packets, returns count of handled. Naming scheme I use is bad, I know :(*/
srRcvBase = (byte)(srRcvBase + ProcessValidBufferedSequence(srRcvBase,
DeliverDataSequenceToUpperLayer));
OnDeliver.Invoke(InvokeReason.Debug, "Receiver window moved. " + PrintSRDebugInfo());
}
}
}
}
}
else
{
//This Kurose implementation will ignore corrupted packets and relies on timeout to recover
//Alternative is to send SREPEAT-control message to request retransmission for seqnum-1 packet.
OnDeliver?.Invoke(InvokeReason.Error, "Received corrupted");
}
}