No print job appears
- Confirm the application header says the listener is running.
- Verify the POS destination uses the emulator computer’s IPv4 address and RAW TCP port
9100. - For same-PC testing, try
127.0.0.1. For another device, do not use localhost; use the Windows computer’s LAN address. - Check that Windows Firewall allows POS Printer Emulator on the current private network.
- Confirm another application is not already using port 9100.
A blank receipt appears
A job can contain printer initialization or status commands without printable text. Open Raw data to confirm bytes arrived, then inspect Commands. If the list contains only initialization, feed, or status instructions, the POS did not send printable receipt content in that connection.
Text is misaligned or the wrong size
- Look for
ESC aalignment commands before the affected line. - Check
ESC !andGS !character-size commands. - Verify the POS resets formatting with
ESC @or explicit mode commands between sections. - Inspect absolute and relative position commands when columns drift unexpectedly.
Accented or international characters are wrong
Open Commands and find ESC t n. The selected code page must match the bytes generated by the POS. The emulator supports common DOS, Windows, and regional code pages; UTF-8 text sent without an ESC/POS-compatible encoding selection may render incorrectly.
A logo, barcode, or QR code does not render
- Confirm the entire graphics command arrived in one complete job; truncated payloads are flagged.
- For raster images, check width, height, and declared byte length.
- For barcodes, verify the symbology and data format expected by
GS k. - For QR codes, confirm the POS stores data before issuing the print function in
GS ( k. - Compare the warning offset with Raw data to identify a vendor-specific variation.
The job shows unsupported warnings
Select the warning in Commands and record its offset and hexadecimal bytes. Check the compatibility matrix. A warning does not mean the entire receipt failed—it identifies the specific sequence the current emulator did not reproduce.
The Windows printer queue reports offline
Open POS Printer Emulator before sending the job, confirm the listener state, and disable SNMP status on the Standard TCP/IP port if Windows is waiting for printer-status responses. The queue should use RAW protocol and port 9100.
Do not expose TCP port 9100 directly to the public internet. Keep the listener on a trusted local or development network and use test data that does not contain real payment information.
Collect useful support evidence
Save the application version, source address, job timestamp, unsupported-command count, Raw data, and a screenshot of the receipt preview. These details make a printing problem reproducible without requiring access to the original store printer.