TFTP (Trivial-File Transfer Protocol) uses default port 69. Do not confuse this with FTP, which uses 20 and 21.
Trivial File Transfer Protocol (TFTP) is a simple lockstep File Transfer Protocol which allows a client to get a file from or put a file onto a remote host. One of its primary uses is in the early stages of nodes booting from a local area network. TFTP has been used for this application because it is very simple to implement.
TFTP was first standardized in 1981 and the current specification for the protocol can be found in RFC 1350.