The DHCP server operates on UDP port 67, and the DHCP client operates on UDP port 68. These are privileged ports, and they are reserved for DHCP only.
DHCP stands for Dynamic Host Configuration Protocol. Many networks use DHCP to assign IP addresses to clients when they attempt to connect to the network for the first time. DHCP is suitable for networks that have a large number of devices connecting and disconnecting on a regular basis. This protocol uses UDP instead of TCP because UDP is packet based and quite efficient for transferring small amounts of data. However, UDP packets have no built-in ordering or error checking.