Simple file transfer with TFTP, often used for network equipment and PXE booting.
What is port 69 used for?
TFTP entry point used to receive the initial read or write request.
Transport protocol
UDP
Role and operation
The client sends its initial request to UDP 69 on the server. The server then replies from a newly selected UDP port, and subsequent DATA/ACK blocks use that negotiated port pair. A firewall therefore needs to track the TFTP session or correctly allow the negotiated ports.
Security precautions
Should this port be opened in the firewall?
Allow UDP 69 only between expected clients and servers. Account for the dynamic UDP port selected by the server after the initial request; stateful TFTP inspection is often preferable to broad port exposure.
How to verify this port
Do not test TFTP with Test-NetConnection -Port 69, because that command tests TCP. Use a TFTP client to read or write an authorized test file, then inspect logs or a packet capture showing the initial UDP 69 request and the negotiated transfer port.
Port/service mappings are common conventions. An application can be configured to use a different port.