/// <summary>
/// Given an outgoing packet, return the server's response.
/// </summary>
/// <param name="toSend">The packet to send to the server.</param>
/// <returns>The server's response to the given packet.</returns>
private TFTPPacket ReceiveDatagram(TFTPPacket toSend)
{
byte[] bytes = toSend.GetBytes();
this._con.Send(bytes, bytes.Length);
byte[] resp;
try
{
resp = this._con.Receive(ref this._remoteEP);
}
catch (SocketException se)
{
throw new Exception("Failed to get a response from the server.", se);
}
short respCode = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(resp, 0));
if ((Opcode)respCode == Opcode.DATA)
{
short blockNum = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(resp, 2));
byte[] data = new byte[resp.Length - 4];
Array.Copy(resp, 4, data, 0, resp.Length - 4);
return(new DataPacket(blockNum, data));
}
else if ((Opcode)respCode == Opcode.ERROR)
{
short errNum = IPAddress.NetworkToHostOrder(BitConverter.ToInt16(resp, 2));
string msg = BitConverter.ToString(resp, 4);
return(new ErrorPacket(errNum, msg));
}
else
{
throw new Exception(String.Format("Unexpected response from server: code {0}", respCode));
}
}
/// <summary>
/// Retrieve the client's target file and write it to the local directory.
/// </summary>
public void RetrieveAndWrite()
{
if (!Connected)
{
throw new Exception(
String.Format("Remote connection is not initialized, so {0} cannot be retrieved.", this._fileName)
);
}
TFTPPacket datagram;
if (this._reqType == RequestType.Error)
{
datagram = new RequestCorruptedPacket(this._fileName);
}
else
{
// implicitly with no error
datagram = new RequestPacket(this._fileName);
}
TFTPPacket response = ReceiveDatagram(datagram);
if (response.Opcode == Opcode.DATA)
{
HandleData((DataPacket)response);
}
else
{
// implicitly an error packet
ReportError((ErrorPacket)response);
}
}