public void WaitForSynAck()
{
EndPoint sender = (EndPoint)_endPoint;
var ackn = new byte[RPH.GetPacketByteLength()];
// set the timeout for receiving acks (retransmission timeout)
_sendingSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReceiveTimeout, Timeout);
try
{
_sendingSocket.ReceiveFrom(ackn, ref sender);
var rph = RPH.Deserialize(ackn);
if (IsCorrupt(rph) || !IsSynAck(rph))
{
_currentState = State.EstablishConnection;
return;
}
else
{
Console.WriteLine("Connection Established");
_currentState = State.SendPacket;
}
}
catch (SocketException e)
{
if (e.SocketErrorCode == SocketError.TimedOut)
{
Console.WriteLine(e.ToString());
Console.WriteLine("No Connection could be established");
}
_currentState = State.EstablishConnection;
}
}
public void SetChecksum(ref byte[] packet)
{
RPH rph = RPH.Deserialize(packet);
var md5 = MD5.Create();
rph._checksum = BitConverter.ToInt32(md5.ComputeHash(packet), 0);
byte[] newHead = rph.Serialize();
Array.Copy(newHead, packet, newHead.Length);
}
private void WaitForAck()
{
EndPoint sender = (EndPoint)_endPoint;
var ackn = new byte[RPH.GetPacketByteLength()];
_tries++;
if (MaxRetransTries < _tries)
{
_currentState = State.FatalError;
return;
}
try
{
_sendingSocket.ReceiveFrom(ackn, ref sender);
var rph = RPH.Deserialize(ackn);
// Ack is corrupt
if (IsCorrupt(rph, ackn) || !IsAck(rph))
{
// If Ack is corrupt resend Packet
Console.WriteLine("Corrupt or NAck: Resend Packet");
}
else if (IsAck(rph) && !IsCorrupt(rph) && rph._ackNr != _localSeqNr)
{
_tries = 0;
Debug.Assert(rph != null, "rph != null");
_localSeqNr += _filechunk.Length;
_currentState = State.SendPacket;
}
else
{
Console.WriteLine("Not defined");
}
}
catch (SocketException e)
{
if (e.SocketErrorCode == SocketError.TimedOut)
{
// Timeout: Resend Packet
Console.WriteLine("Timeout: Resend Packet");
SendOnePacket();
}
else
{
Console.WriteLine("Fatal Error");
_currentState = State.FatalError;
return;
}
}
}
public bool IsCorrupt(RPH rph, byte[] packet)
{
var copyPacket = new byte[packet.Length];
Array.Copy(packet, copyPacket, packet.Length);
var recvRph = RPH.Deserialize(packet);
int recvChecksum = recvRph._checksum;
recvRph._checksum = 0;
byte[] newHead = recvRph.Serialize();
Array.Copy(newHead, copyPacket, newHead.Length);
var md5 = MD5.Create();
int calcChecksum = BitConverter.ToInt32(md5.ComputeHash(copyPacket), 0);
return(calcChecksum != recvChecksum);
}
