From SpinetiX Support Wiki
writeCOMPort function to send characters to the serial printer.
Most printers these days are connected to a local network and support the Internet Printing Protocol (IPP), which is based on the Hypertext Transfer Protocol (HTTP), thus you could use Ajax calls to submit print jobs to that printer. For instance, you can print a file from a network resource (including from an HMP) specified by its URI. Moreover, that URI could point to a web page (php script) that receives parameters in the link and generates the document / page that needs to be printed.