DHCP is a connectionless protocols.

In general, any protocol that is based on TCP port alone is a connection-oriented protocol while any protocol that is based on UDP port alone is a connectionless protocol.

And a protocols that can work on both TCP and UDP port can be either a connection-oriented or a connectionless protocol depending upon the which protocol is used (TCP or UDP).

For checking other protocols if they are connection-oriented or connectionless check

http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers

UDP!

Different from a connectionless protocol, a connection-oriented protocol guaranties the delivery of the information. An example of connection-oriented protocol is (TCP) and a connectionless protocol is (UDP). TCP is a connection-oriented protocol, it makes a connection and checks whether the data is received, and resends if it is not. UDP is a connectionless protocol, it does not guarantee delivery by first connecting and checking whether data is received.

In internet protocol suite UDP is the connectionless protocol. There is no initial communication between client and server. UDP will not check whether the transmission was successful.

Connectionless protocols