OP, are you sure that your printer has a serial port? That would be somewhat unusual I think, back in the day when I used many dot matrix printers, they all had parallel (Centronics) ports. The same model printer in the one eBay listing I found (sold, maybe bought by you?) also has a parallel port, clearly visible in a photo of its backside.
Even though they typically came with Centronics ports, you could often add an additional interface. The Epson-compatible OKI printer I have can use an additional interface board (of which I have one) and have both a serial and parallel interface. And of course there are also those console printers which uses serial like the DEC LA printer mentioned in a sibling comment.
