fall back to common alternate ports if a port refuses connection

[nixon575483975846342]

port 81 is a commonly used port for http for iot devices. the http signature checks only port 80 and does not check port 81 if the connection is refused. i would like to request using this fallback port if 80 is closed.

There are probably other ports that are like this, but I can't think of them offhand right now.

[trylinux]

Currently, additional ports can be scanned using the -p flag.

[nixon575483975846342]

i know, but specifically the port 81 is something i see so commonly that i think should be included by default