If memoery server, "Dispatch_input" is a function
in LRPng.
Ah yes:
[chris@localhost drm]$ grep "Dispatch_input" /usr/sbin/lpd
Binary file /usr/sbin/lpd matches
.
It's an attempt to exploit the format string bug
I found in LPRng

As Chris says, it's attempting to exploit the LPRng security hole; if
you're up to date with the errata (or have installed the 'respin' version
of 7.0), you should be fine, as this particular hole has been fixed.