private void ProcessClient(TcpClient client, TcpListener listener, ScopedActivity activity)
{
ListenerInfo info = _ListenerInfos[listener];
try
{
info.Clients.Add(client);
//gather some metrics...
activity.Log("Client: {0}", client.Client.RemoteEndPoint);
activity.Log("Active Connections for Listener: {0}", info.Clients.Count);
//run validation checks...
if (ValidateClient(client, activity))
{
//process client
activity.Log("Exchanging Commands");
using (SmtpStreamProcessor clientProcessor = new SmtpStreamProcessor(client.GetStream(), info.SecurityMode, ServerCertificate))
{
clientProcessor.Process();
}
}
}
finally
{
info.Clients.Remove(client);
client.Close();
}
}
private bool ValidateClient(TcpClient client, ScopedActivity activity)
{
bool retVal = false;
activity.Log("Checking if client IP Address is black listed");
IPEndPoint clientEndpoint = (IPEndPoint)client.Client.RemoteEndPoint;
if (!BlackListedIpAddresses.Contains(clientEndpoint.Address))
{
//address is not black listed
activity.Log("Address {0} is allowed, client passes validation checks", clientEndpoint.Address);
retVal = true;
}
else
{
//address is black listed
activity.Log("Not Processing Client, Client IP Address is black listed: {0}", clientEndpoint.Address);
}
return retVal;
}
private void AcceptClient(IAsyncResult result)
{
using(ScopedActivity localActivity = new ScopedActivity("Accepting Client Connection"))
{
TcpClient client = null;
TcpListener listener = (TcpListener)result.AsyncState;
//this section is critical for the robustness of the application.
//it should only accept the client and begin accepting new connections
//in the finally block
try
{
localActivity.Log("Listener: {0}", listener.LocalEndpoint);
client = listener.EndAcceptTcpClient(result);
}
catch (Exception ex)
{
localActivity.LogException(ex, "An exception occurred while accepting client connection");
}
finally
{
listener.BeginAcceptTcpClient(AcceptClient, listener);
}
//if client was successfully accepted, continue the processing chain
if (client != null)
{
ProcessClient(client, listener, localActivity);
}
}
}