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);
}
public bool IsCorrupt(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);
}
public bool Init()
{
_acknowledgedBytes = 0;
_fileEnding = "";
_fileRecv = false;
NrPackets = 0;
DisplayServerInformation();
Console.WriteLine("Warte auf Verbindung von Clienten...");
_sender = new IPEndPoint(IPAddress.Any, 0);
IPEndPoint endAddress = new IPEndPoint(IPAddress.Any, ListenPort);
try
{
if (_udpClient == null)
{
_udpClient = new UdpClient(endAddress);
}
byte[] dgram = _udpClient.Receive(ref _sender);
RPH rph = RPH.Deserialize(dgram);
if (IsCorrupt(rph))
{
// send nak
return(false);
}
else
{
_currentState = State.SendSynAck;
}
_fileEnding = rph._fileEnding;
_payloadBuffer = new byte[rph._fileSize];
return(true);
}
catch (SocketException e)
{
Console.WriteLine(e);
return(false);
}
}
public void AckPacket(byte[] buf)
{
// Deserialize our protocol
var rph = RPH.Deserialize(buf);
// Calculate the size of our protocol
int headSize = rph.GetByteLength();
// if received packet is a retransmission or corrupt or packet reordering took place
if (IsCorrupt(buf) || _acknowledgedBytes != rph._seqNr)
{
// Send NAck
Console.WriteLine("Packet was corrupt or it was a retransmission");
var ack = RPH.CreateNAckPacket();
var dgram = ack.Serialize();
SetChecksum(ref dgram);
_udpClient.Send(dgram, dgram.Length, _sender);
}
else if (!IsCorrupt(buf) && rph._seqNr == _acknowledgedBytes)
{
_acknowledgedBytes = rph._seqNr + buf.Length - headSize;
// Copy received bytes into receive buffer
Array.Copy(buf, headSize, _payloadBuffer, rph._seqNr, buf.Length - headSize);
var ack = RPH.CreateAckPacket(_acknowledgedBytes, 0);
var dgram = ack.Serialize();
SetChecksum(ref dgram);
_udpClient.Send(dgram, dgram.Length, _sender);
if (_payloadBuffer.Length == _acknowledgedBytes)
{
_currentState = State.SaveToFile;
}
}
else
{
Console.WriteLine("Not defined");
}
NrPackets++;
// Console.WriteLine(NrPackets + ".Paket");
// Console.WriteLine("Sequenznummer: " + rph._seqNr);
// Console.WriteLine("AckNr: " + _acknowledgedBytes);
}