TCP BinaryFormatter Deserialize To File?

I always 'write' an emty file, not sure exacty where I went wrong, help!

[Sending]
tcpClient = new TcpClient();
tcpClient.Connect(IPAddress.Parse("192.168.1.7"), 5000);
NetworkStream ns = tcpClient.GetStream();
IFormatter bf = new BinaryFormatter();
bf.Serialize(ns,"test.txt");
tcpClient.Close();

[Receiving]
listener = new TcpListener(IPAddress.Any, 5000);
listener.Start();
                       
while ((client = listener.AcceptTcpClient()) != null)
{
     NetworkStream ns = client.GetStream();
     object obj = null;

     if (ns.DataAvailable)
     {
           try
           {
                  IFormatter bf = new BinaryFormatter();
                  obj = bf.Deserialize(ns);
           }
           finally
           {                            
                  StreamWriter sw = new StreamWriter(new FileStream("test.txt", FileMode.Create, FileAccess.Write, FileShare.Read));
                  sw.WriteLine(obj.ToString());
           }
     }