The remote host is running a Teredo server. Teredo is a protocol for tunneling IPv6 over UDP, and is used to give nodes the ability to obtain IPv6 connectivity behind IPv4 network address translation (NAT) devices. A Teredo server is a node that is connected to both IPv4 and IPv6 networks.
Solution
Limit incoming traffic to this port if desired. When full IPv6 connectivity is available, the Teredo server should be disabled.