The source and destination ports in UDP fulfill a very similar role as they do in TCP. The UDP protocols and their associated ports are as follows:
| Port number | Application | Acronym |
| 53 | Domain Name Service | DNS |
| 67 | Dynamic Host Configuration Protocol (Server) | DHCP |
| 68 | Dynamic Host Configuration Protocol (Client) | DHCP |
| 69 | Trivial File Transfer Protocol | TFTP |
| 161 | Simple Network Management Protocol | SNMP |
Table 5.2: Well-known port numbers in the UDP protocol. These are the default ports for these applications, although some servers might use registered ports, or even non-standard ports, depending on their security posture.
Again, the ports are specific to the protocol, so UDP datagrams can be directed to the correct place just by the port number.