Create A Windows Service That Listens To A Port For Data?

I'm experiencing a weird problem. I need to create a Windows service that listens to a port for data. The data is comma separated, so I need to split it up and just write a few of the separated values to a file. This is a brief summary of my code:-

Do While True

tcpClient = tcpListener.AcceptTcpClient()
networkStream = tcpClient.GetStream()
Dim bytes(tcpClient.ReceiveBufferSize) As Byte

[code]....

Now the above code works fine. But suppose I just want to write only (2) to file i.e 2 of the comma separated values, problems arise. This is what happens:-

If I include both lines (1) and (2), output file = lines (1) and (2)
If I include only line (1) and comment out (2), output file = line (1)
If I include only line (2) and comment out (1), output file = BLANK ???