Usually barcode scanners are configurable to act as a "keyboard
wedge" (i.e., a virtual keyboard), as if the user has typed the
barcode, optionally followed by a <tab> or <enter> key. This
suffices for most use-cases. The only time I've found that it
doesn't work well is if the app needs to accept input when the app
isn't focused (because the barcode input goes into the foreground
app). In such a case, you'd have to use client-side API code (a
Windows, Mac, iOS, Android, Linux program to talk directly to the
scanner even when it's in the background).
-tkc