My ultimate goal is to send a print job to the printer via the Internet. The trick is that the printer is connected directly to the router, so I cannot count on computer processing.
The path to the print job: Computer → Internet → Router → Printer
The printer is an Epson TM-T88V with a UB-E02 plug-in (it originally came with a 25-pin module).
The router is a D-Link DIR-655 with port 9500 redirected to the LAN port 9100 and the IP address of the LAN printer. Using this setting, I can enter the IP address of the WAN router + port 9500 in a web browser, and the printer issues an HTTP request that it receives.
From the terminal, if I use lpr (specifically lpr -h ip-address: 9500 filename.txt), the printer prints the HTTP request it receives (and not the file), and lpr seems to just wait for a response. According to the UB-E02 Technical Reference, the Connect-It module supports lp / lpr.
Why does the printer print an HTTP request and not send a response?
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