How to print a file to Network Thermal Printer

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http://askubuntu.com – Im developing an POS application and need to print a text(generic-text) file to a thermal printer connected to a Router. Please find the below image for clear understanding. Descriptions: PC running with Ubuntu Linux Wireless ADSL Router Thermal Printer Model( Citizen S-651 with Ethernet card) I need to print a file for my POS application to a thermal printer. Please guide me. Thanks in Advance (HowTos)