Document Marked With an Error

A document drawn with a red border contains at least one error the parser recorded while reading your byte stream. The rest of the document still renders; the border marks that something in it did not add up.

Reading the error

• A warning triangle appears next to the document. Hover it to see the error text.
• Or switch on Raw Data for that document to see the byte stream alongside the parsed elements, with the failure in place. This is the faster route when you need to know where in the receipt it went wrong rather than just what happened.

Most messages are self-explanatory: an argument outside the range the command allows, a length that does not match the data that followed, a command cut short by the connection closing mid-sequence.

When it is your byte stream

Common causes, in order:

• A truncated job. The connection closed in the middle of a command. Usually an application that times out or exits without flushing.
• An out-of-range argument. For example a colour byte where the command only allows 0/48 and 1/49.
• Wrong protocol. EPL sent to an ESC/POS printer produces a document full of errors rather than a label. See Printer protocols.

When it is us

The parser may also flag a command it does not implement yet. ESC/POS is large, vendors extend it, and some sequences are undocumented - so an error does not automatically mean your client is wrong.

If the command looks correct against the specification, write to support@virtual-printer.online with the document and the bytes. Adding a command is usually quick, and a real byte stream from the field is exactly what makes that possible.