udp(4P) - man - phpMan

rpc_soc (3t)         - "library routines for remote procedure calls"
ip-fou (8)           - Foo-over-UDP receive port configuration
ip-gue (8)           - Generic UDP Encapsulation receive port configuration
nc (1)               - arbitrary TCP and UDP connections and listens
nc.openbsd (1)       - arbitrary TCP and UDP connections and listens
nc_openbsd (1)       - arbitrary TCP and UDP connections and listens
Net::Server::Proto::UDP (3pm) - Net::Server UDP protocol.
netcat (1)           - arbitrary TCP and UDP connections and listens
udp (7)              - User Datagram Protocol for IPv4
udplite (7)          - Lightweight User Datagram Protocol