protected override void DoProtocol()
{
Packet[] buffer = new Packet[_MAX_SEQ + 1]; /* buffers for the outbound stream */
byte ackExpected = 0; /* oldest frame as yet unacknowledged */
byte nextFrameToSend = 0; /* MAX SEQ > 1; used for outbound stream */
byte frameExpected = 0; /* next frame expected on inbound stream */
byte nbBuffered = 0; /* number of output buffers currently in use */
// Creates events that trigger the thread changing
var waitHandles = new WaitHandle[]
{
_closingEvents[_actorType], _networkLayerReadyEvents[_actorType], _frameArrivalEvents[_actorType],
_frameErrorEvents[_actorType], _frameTimeoutEvents[_actorType]
};
/* allow network layer ready events */
EnableNetworkLayer();
var running = true;
while (running)
{
// Wait trigger events to activate the thread action
var index = WaitHandle.WaitAny(waitHandles);
// Execute the task related to the event raised
switch (index)
{
case _STOP_RUNNING:
// Received the closing event (_closingEvent)
running = false;
break;
case _NETWORK_LAYER_READY:
// The network layer has a packet to send (_networkLayerReadyEvent)
// In our case, a new packet read from the input file
// Accept, save, and transmit a new frame.
// Fetch new packet
nbBuffered++; /* expand the sender’s window */
if (nbBuffered < _MAX_SEQ)
{
EnableNetworkLayer();
}
else
{
DisableNetworkLayer();
}
buffer[nextFrameToSend] = FromNetworkLayer();
SendData(nextFrameToSend, frameExpected, buffer); /* transmit the frame */
nextFrameToSend = Inc(nextFrameToSend); /* advance sender’s upper window edge */
break;
case _FRAME_ARRIVAL:
// A data or control frame has arrived (_frameArrivalEvent)
// In our case, a new packet to write to the output file or received an ack
// get incoming frame from physical layer
//var r = FromPhysicalLayer(); /* scratch variable */
var a = FromPhysicalLayer(); /* scratch variable */
//Decode frame and correct errors using Hamming protocol
var r = Hamming.decodeHamming(a);
if (r == null)
{
// _frameErrorEvents[(byte)(1 - _threadId)].Set();
break; //reject frame
}
if (r.Seq == frameExpected)
{
// Frames are accepted only in order.
ToNetworkLayer(r.Info); /* pass packet to network layer */
frameExpected = Inc(frameExpected); /* advance lower edge of receiver’s window */
}
// Ack n implies n − 1, n − 2, etc.Check for this.
while (Between(ackExpected, r.Ack, nextFrameToSend))
{
// Handle piggybacked ack.
nbBuffered--; /* one frame fewer buffered */
StopTimer(ackExpected); /* frame arrived intact; stop timer */
ackExpected = Inc(ackExpected); /* contract sender’s window */
}
break;
case _CKSUM_ERROR:
// Just ignore bad frames (_frameErrorEvent)
break;
case _TIMEOUT:
// Trouble; retransmit all outstanding frames (_frameTimeoutEvent)
nextFrameToSend = ackExpected; /* start retransmitting here */
for (byte i = 1; i <= nbBuffered; i++)
{
SendData(nextFrameToSend, frameExpected, buffer); /* resend frame */
nextFrameToSend = Inc(nextFrameToSend); /* prepare to send the next one */
}
break;
}
if (nbBuffered < _MAX_SEQ)
{
EnableNetworkLayer();
}
else
{
DisableNetworkLayer();
}
}
Console.WriteLine(string.Format("**** The Data Link Layer of the {0} thread terminated ****", _actorType));
}
protected override void DoProtocol()
{
byte ackExpected = 0; /* lower edge of sender's window */
byte nextFrameToSend = 0; /* upper edge of sender's window */
byte frameExpected = 0; /* lower edge of receiver's window */
byte tooFar = _NR_BUFS; /* upper edge of receiver's windows*/
Packet[] outBuffer = new Packet[_NR_BUFS]; /* buffers for the outbound stream */
Packet[] inBuffer = new Packet[_NR_BUFS]; /* buffers for the inboound stream */
bool[] arrived = new bool[_NR_BUFS];
for (int i = 0; i < _NR_BUFS; i++)
{
arrived[i] = false;
}
byte nbBuffered = 0; /* number of output buffers currently in use */
// Creates events that trigger the thread changing
var waitHandles = new WaitHandle[]
{
_closingEvents[_actorType], _networkLayerReadyEvents[_actorType], _frameArrivalEvents[_actorType],
_frameErrorEvents[_actorType], _frameTimeoutEvents[_actorType], _ackTimeoutEvent
};
/* allow network layer ready events */
EnableNetworkLayer();
var running = true;
while (running)
{
// Wait trigger events to activate the thread action
var index = WaitHandle.WaitAny(waitHandles);
// Execute the task related to the event raised
switch (index)
{
case _STOP_RUNNING:
// Received the closing event (_closingEvent)
running = false;
Console.WriteLine("EVENT STOP RUNNING");
break;
case _NETWORK_LAYER_READY:
// The network layer has a packet to send (_networkLayerReadyEvent)
// In our case, a new packet read from the input file
// Accept, save, and transmit a new frame.
// Fetch new packet
nbBuffered++; /* expand the window */
if (nbBuffered < _NR_BUFS)
{
EnableNetworkLayer();
}
else
{
DisableNetworkLayer();
}
outBuffer[nextFrameToSend % _NR_BUFS] = FromNetworkLayer();
SendData(FrameKind.Data, nextFrameToSend, frameExpected, outBuffer); /* transmit the frame */
nextFrameToSend = Inc(nextFrameToSend); /* advance upper window edge */
break;
case _FRAME_ARRIVAL:
// A data or control frame has arrived (_frameArrivalEvent)
// In our case, a new packet to write to the output file or received an ack
// get incoming frame from physical layer
var a = FromPhysicalLayer(); /* scratch variable */
//Decode frame and correct errors using Hamming protocol
var r = Hamming.decodeHamming(a);
if (r == null)
{
// goto case _CKSUM_ERROR;
break; //reject frame
}
if (r.Kind == FrameKind.Data)
{
if ((r.Seq != frameExpected) && _no_nak)
{
SendData(FrameKind.Nak, 0, frameExpected, outBuffer);
}
else
{
StartAckTimer();
}
if (Between(frameExpected, r.Seq, tooFar) && (arrived[r.Seq % _NR_BUFS] == false))
{
arrived[r.Seq % _NR_BUFS] = true; //mark buffer as full
inBuffer[r.Seq % _NR_BUFS] = r.Info; //insert data
while (arrived[frameExpected % _NR_BUFS])
{
ToNetworkLayer(inBuffer[frameExpected % _NR_BUFS]);
_no_nak = true;
arrived[frameExpected % _NR_BUFS] = false;
frameExpected = Inc(frameExpected);
tooFar = Inc(tooFar);
StartAckTimer();
}
}
}
if ((r.Kind == FrameKind.Nak) && Between(ackExpected, (byte)((r.Ack + 1) % (_MAX_SEQ + 1)), nextFrameToSend))
{
SendData(FrameKind.Data, (byte)((r.Ack + 1) % (_MAX_SEQ + 1)), frameExpected, outBuffer);
}
while (Between(ackExpected, r.Ack, nextFrameToSend))
{
nbBuffered--;
StopTimer(ackExpected % _NR_BUFS); /* frame arrived intact; stop timer */
ackExpected = Inc(ackExpected); /* contract sender’s window */
_oldest_frame = ackExpected;
}
break;
case _CKSUM_ERROR:
if (_no_nak)
{
SendData(FrameKind.Nak, 0, frameExpected, outBuffer); //damaged frame
}
break;
case _TIMEOUT:
SendData(FrameKind.Data, _oldest_frame, frameExpected, outBuffer);
break;
case _ACK_TIMEOUT:
SendData(FrameKind.Ack, 0, frameExpected, outBuffer);
break;
}
if (nbBuffered < _NR_BUFS)
{
EnableNetworkLayer();
}
else
{
DisableNetworkLayer();
}
}
Console.WriteLine(string.Format("**** The Data Link Layer of the {0} thread terminated ****", _actorType));
}