I have a problem in the secure network stream returned by the method SecureTcpListener.GetStream().
It always raises the exception (Object refrence not set to an instance of an object)when trying to read from the network stream using the method SecureNetworkStream.Read().

Can you post the source code you're using right now that throws the exceptions..?

// Client's code
static void Main(string[] args)
{
byte[] message = Encoding.ASCII.GetBytes("server helloooooo");
SecurityOptions so = new SecurityOptions(SecureProtocol.None);
SecureTcpClient sc = new SecureTcpClient("node4",5005,so);


SecureNetworkStream ns = sc.GetStream();


ns.Write(message,0,message.Length);
Console.WriteLine("data sent");
ns.Close();
sc.Close();
Console.Read();
}
//Server's code
static void run()
{
byte[] message = null;
SecurityOptions so = new SecurityOptions(SecureProtocol.None);
SecureTcpListener s = new SecureTcpListener(5005,so);
s.Start();
SecureTcpClient sc = s.AcceptTcpClient();
SecureNetworkStream ns = sc.GetStream();
try
{
ns.Read(message,0,message.Length);
Console.WriteLine("data received ");
Console.WriteLine(Encoding.ASCII.GetString(message));
}
catch(Exception e)
{
Console.WriteLine(e.Message.ToString());
}
sc.Close();
s.Stop();
Console.Read();
}

The ArgumentNullException is because you use the message parameter without initializing it to a valid array of bytes.
You should change the declaration of message to something like this:
byte[] message = new byte[1024];