"Decode as" don't work well for modbus

This issue was migrated from bug 10933 in our old bug tracker.

Original bug information:

Reporter: hel…@‍126…
Status: RESOLVED FIXED
Product: Wireshark
Component: Common utilities (libwsutil)
OS: Windows 7
Platform: x86-64
Version: 1.12.3

Attachments:

: can't be resolved
: after change the standard port in option-protocols