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.
Limit incoming traffic to this port if desired. When full IPv6 connectivity is available, the Teredo server should be disabled.