/// <inheritdoc />
public override async Task <bool> IsAvailableAsync()
{
var hello = new AnnounceRequest
{
ClientAddress = LocalEndPoint.Address
};
try
{
var res = await SendAndReceiveAsync(hello);
var response = Message.Create <Response>(res);
switch (response.ResultCode)
{
case 0:
if (response.Version == ProtocolVersion)
{
UnavailableReason = "";
return(true);
}
UnavailableReason = "Protocol version not support.";
return(false);
case 2:
UnavailableReason = "Unathorised";
return(false);
default:
UnavailableReason = $"Error code {response.ResultCode}.";
return(false);
}
}
catch (TimeoutException)
{
UnavailableReason = "No response received.";
return(false);
}
catch (Exception e)
{
UnavailableReason = $"Unexpected exception '{e.GetType().FullName}'. {e.Message}.";
return(false);
}
}
/// <summary>
/// Create a message from the specified datagram.
/// </summary>
/// <param name="datagram">
/// The byte array containing the message.
/// </param>
/// <returns>
/// A <see cref="Message"/> that represents the <paramref name="datagram"/>.
/// </returns>
public static Message Create(byte[] datagram)
{
if (datagram == null || datagram.Length < 4)
{
throw new InvalidDataException("NAT-PCP datagram must be at least 4 bytes.");
}
using (var ms = new MemoryStream(datagram, false))
{
// Get the type of message.
var reader = new NatReader(ms);
var header = new Message();
header.Read(reader);
Message msg = null;
if (header.IsResponse)
{
switch (header.Opcode)
{
case Opcode.Announce:
msg = new Response(); // no specific response data
break;
case Opcode.Map:
msg = new MapResponse();
break;
case Opcode.Peer:
msg = new Response(); // TODO
break;
default:
throw new NotSupportedException($"NAT-PCP response with opcode {header.Opcode}.");
}
}
else
{
switch (header.Opcode)
{
case Opcode.Announce:
msg = new AnnounceRequest();
break;
case Opcode.Map:
msg = new MapRequest();
break;
case Opcode.Peer:
msg = new PeerRequest();
break;
default:
throw new NotSupportedException($"NAT-PCP request with opcode {header.Opcode}.");
}
}
// Read the message data.
reader.Position = 0;
msg.Read(reader);
return(msg);
}
}
