I have just compiled the Java example from Epson and downloaded it to my phone, it is attempting to connect over TCP-IP to a printer which I won't have until Monday.
The example which boastrike suggested can use an event in dotnet (folderevent I think) which monitors a particular folder you can then read in the file format it and then you can print directly to your Receipt Printer on your network also. You also have a backup copy of the orders. Does your App connect already to a server to upload the orders ? I prefer this way of doing things rather than have the tablet talk directly to the printer. There are something to need to watch out for with this approach mainly files being received while it is currently processing a receipt file.
This is probably a better way of doing it as you will need to get the info across to your server in order to populate your order table on the server. You can 'Kill two Birds with the one stone' so to say !!.
If you want a copy of the Epson App let me know and I can get a copy across to you to test it.
Regards
BOB