I think that you are mistaken in thinking that ttyS0 has anything to do with the NAS’s USB system. Its name looks more like a regular serial port, probably one that can only be reached by connecting to jumpers on the NAS’s motherboard. (This is very common on embedded hardware.)
How do I open up port 49402 in linux ?
It’s not clear what you mean by “open up”. If you mean, what causes the port to be listened to for incoming connections, then ser2net does that. If you are talking about a firewall on the Linux machine blocking incoming connections, assuming you have one, then you will need to find the firewall configuration and turn off the firewall (seriously, firewalls on Unix machines inside your LAN aren’t any kind of security, just turn them off).
How do I check and ensure that ser2net is running ? - [i](I tried 'ps aux | less' but could not see it) [/i]
That should show ser2net. If it isn’t then ser2net isn’t running. ser2net has some command-line options that will stop it detaching into the background when you run it; these are useful with debugging. You can use ctrl-C to kill a running program in Linux, just as you do in a DOS shell.
Also you can speak to ser2net over the LAN with telnet:
telnet the-nas 49402For the CurrentCost you’ll see the long XML strings every few seconds.