private void UdpReceiveCompleted(IAsyncResult ar)
{
DnsAsyncState state = (DnsAsyncState)ar.AsyncState;
if (state.Timer != null)
{
state.Timer.Dispose();
}
if (state.TimedOut)
{
state.ServerIndex++;
UdpBeginSend(state);
}
else
{
byte[] responseData = state.UdpClient.EndReceive(ar, ref state.UdpEndpoint);
state.UdpClient.Close();
state.UdpClient = null;
state.UdpEndpoint = null;
state.Response = new DnsMessage();
state.Response.Parse(responseData, false, state.TSigKeySelector, state.TSigOriginalMac);
if (state.Response.ReturnCode == ReturnCode.ServerFailure)
{
if (state.ServerIndex++ < state.Servers.Count)
{
UdpBeginSend(state);
return;
}
else
{
state.SetCompleted();
}
}
else
{
if (state.Response.IsTruncated)
{
TcpBeginConnect(state);
return;
}
else
{
state.SetCompleted();
}
}
}
}
private void TcpBeginConnect(DnsAsyncState state)
{
if (state.ServerIndex == state.Servers.Count)
{
state.Response = null;
state.TcpStream = null;
state.TcpClient = null;
state.SetCompleted();
return;
}
IPAddress server = state.Servers[state.ServerIndex];
state.TcpClient = new TcpClient(server.AddressFamily);
state.TimedOut = false;
IAsyncResult asyncResult = state.TcpClient.BeginConnect(server, _DNS_PORT, TcpConnectCompleted, state);
state.Timer = new Timer(TcpTimedOut, asyncResult, QueryTimeout, Timeout.Infinite);
}
private void UdpBeginSend(DnsAsyncState state)
{
if (state.ServerIndex == state.Servers.Count)
{
state.Response = null;
state.UdpClient = null;
state.UdpEndpoint = null;
state.SetCompleted();
return;
}
state.UdpEndpoint = new IPEndPoint(state.Servers[state.ServerIndex], _DNS_PORT);
state.UdpClient = new UdpClient(state.UdpEndpoint.AddressFamily);
state.UdpClient.Connect(state.UdpEndpoint);
state.TimedOut = false;
IAsyncResult asyncResult = state.UdpClient.BeginSend(state.QueryData, state.QueryLength, UdpSendCompleted, state);
state.Timer = new Timer(UdpTimedOut, asyncResult, QueryTimeout, Timeout.Infinite);
}
private void TcpReceiveCompleted(IAsyncResult ar)
{
DnsAsyncState state = (DnsAsyncState)ar.AsyncState;
if (state.Timer != null)
{
state.Timer.Dispose();
}
if (state.TimedOut)
{
state.ServerIndex++;
TcpBeginConnect(state);
}
else
{
state.TcpStream.EndRead(ar);
state.TcpStream.Close();
state.TcpClient.Close();
state.TcpStream = null;
state.TcpClient = null;
state.TcpBuffer = null;
state.Response = new DnsMessage();
state.Response.Parse(state.TcpBuffer, false, state.TSigKeySelector, state.TSigOriginalMac);
if ((state.Response.ReturnCode == ReturnCode.ServerFailure) && (state.ServerIndex++ < state.Servers.Count))
{
TcpBeginConnect(state);
return;
}
else
{
state.SetCompleted();
}
}
}