Get the actual data length read from network stream

Hi Experts,

I am reading data from a RFID reader using network stream. But the length of the data is always 8193. What can I do to get the actual length.
Thanks in advance.

Dim tcpClient As New TcpClient("192.145.1.80", "10001")
             Dim netStream As NetworkStream = TcpClient.GetStream()
             If netStream.CanRead Then
                 ' Reads the NetworkStream into a byte buffer.
                 Dim bytes(TcpClient.ReceiveBufferSize) As Byte
                 ' Read can return anything from 0 to numBytesToRead.  
                 ' This method blocks until at least one byte is read.
                 netStream.Read(bytes, 0, CInt(TcpClient.ReceiveBufferSize))

                 ' Returns the data received from the host to the console.
                Dim ReturnData As String = Encoding.ASCII.GetString(bytes)
                 TextBox1.Text = ReturnData  'Length is always 8193
                RaiseEvent TCPDataIn(ReturnData)
             Else
                 Console.WriteLine("You cannot read data from this stream.")
                 TcpClient.Close()
                 ' Closing the tcpClient instance does not close the network stream.
                 netStream.Close()
                 Return
             End If