Is it possible to send a byte[] stream to remote listener? in Developer Help
TcpListener tcpServer = new TcpListener(IPAddress.Parse("192.168.1.15"), 5442);
This post has some info, and links to another post with the message byte format:
http://www.byond.com/developer/ forum/?id=701287&display=1#701287
Of course, you could also just write a DLL and use call() to send it more simply.