IP point to point connections are called unicast. Multicast is used to establish point to multi-point IP transmissions.
Unicast can use UDP and TCP as transport protocol. 
UDP unicast connections can be uni- and bidirectional. TCP connections are always bidirectional.
Multicast use the UDP as transport protocol. Multicast transmissions are always unidirectional.
More details about Multicast and its implementation in can be found in application note 9 on Mayah website (www.mayah.com/content/download/pdfs/appnotes/centauri/a_n_e_009.pdf).