Finally, a CygWin package for mosh 1.2.5 is available. Run to your nearest CygWin mirror and update your system.

If you’re new to CygWin, I advise you to select mosh, Perl, and OpenSSH, in addition to the base set of packages selected for you.

You might want to add some new aliases to your .bash_profile file using this as a template:

alias FQDN6='echo -ne "\033]0;mosh IPv6: FQDN\007"; mosh -6 -a -- user@FQDN screen -rx'

I’m of course assuming you want to attach to a screen session immediately after establishing a mosh session. Note, you can’t combine -6 -a into -6a nor -a6, because the argument parsing isn’t clever enough.

Make sure any firewall allows incoming TCP connections to port 22, and incoming UDP connections ranging from port 60000 and up to as many concurrent mosh sessions you deem necessary, with 61000 being the current maximum. In Cisco IOS parlance:

permit tcp any gt 1023 host 2001:db8:1:2::3 eq 22
permit udp any gt 1023 host 2001:db8:1:2::3 range 60000 60005