Transports allow communication between irccd and irccdctl over IP.
Some systems may disable or enable IPv4 fallback by default when using IPv6 sockets. The current code was testing if IPv4 was requested as a fallback, instead it must explicitly disable or enable the IPV6_V6ONLY option even if IPv4 is not requested.
Upgrade to a newer version if applicable or apply one of the following fixes:
If you don't have a local copy:
hg clone -u release-2.1 http://hg.malikania.fr/irccd
If you already have a local copy:
cd /path/to/irccd hg pull hg up release-2.1
And install new version of irccd.
Download the following patch:
cd /path/to/irccd/ patch -p1 < /path/to/20170307.patch