How to Connect to a non PC based ethernet device?

Question

I am trying to write a program that connects to a device(not a computer, NAS, Printer, or other standard device) and need a little bit of direction. It is a TCP device i have tried  a standard socket connection but the connection is denied. There is a password handshake that needs to go on directly after a connection has been made. And i am at a loss as to how to do this. Any help would be appreciated. I am also new to C# and PC programming in general. Thanks in advance for any help.