Port 349 sits in the well-known ports range with an official assignment: MFTP, the Multicast File Transfer Protocol. Both TCP and UDP on port 349 are reserved for this protocol. But here's the thing — MFTP never quite made it.
The Problem MFTP Tried to Solve
Imagine you need to send a 500MB software update to 10,000 computers. The naive approach: send it 10,000 times. That's 5 petabytes of bandwidth. MFTP proposed a better way: send it once using IP multicast, and let the network duplicate the packets only where necessary. Everyone gets the file, but the sender only transmits it once.1
This is the "one-to-many" problem, and it's still a problem today.
How MFTP Works
MFTP operates above UDP and consists of two components:2
Multicast Control Protocol (MCP) — Sets up and tears down multicast sessions, manages group membership, coordinates between sender and receivers.
Multicast Data Protocol (MDP) — Handles the actual reliable transmission of file data to multiple clients simultaneously.
The protocol supports sending files from one sender to potentially thousands (or even millions with network aggregators) of receivers at once over a multicast group.2 It includes built-in reliability mechanisms to ensure all receivers get complete, correct copies of the file despite the lossy nature of UDP and multicast transmission.
The History: Specification Without Adoption
1997 — StarBurst Communications, led by K. Miller and K. Robertson, submits the MFTP specification as an Internet-Draft (draft-miller-mftp-spec).3
2000 — RFC 2887 references MFTP as "Work in Progress" when discussing reliable multicast design.4
After — The Internet-Draft expires. MFTP never becomes an official RFC standard.
Port 349 was assigned to MFTP by IANA with Dave Feinleib listed as the contact.5 The port remains officially reserved for this protocol, even though MFTP never achieved widespread deployment.
Why MFTP Didn't Win
IP multicast is powerful in theory but difficult in practice. It requires support from every router between sender and receivers. Many ISPs don't enable multicast routing because it's complex to manage and creates scaling challenges. Enterprise firewalls often block multicast traffic. NAT breaks it. The Internet's architecture simply wasn't — and largely still isn't — built for efficient multicast at scale.
MFTP needed a different Internet than the one that existed.
What Uses Port 349 Today
Officially: MFTP, according to IANA.5
In practice: Very little. Some sources note that port 349 has been exploited by malware for command and control communications in the past,6 which is common for lower-numbered ports that aren't actively defended by legitimate services.
The port exists as a reserved placeholder for a protocol that remains more specification than reality.
The Broader Lesson
Port 349 represents something important about Internet protocols: getting a port number is easy, but getting a protocol adopted is hard. The technical solution might be elegant, the specification might be solid, but if it requires changes to the Internet's fundamental architecture — like widespread multicast support — it faces an uphill battle.
MFTP tried to solve a real problem. The solution was technically sound. But the Internet had already made different architectural choices, and changing them proved too difficult.
Port 349 remains reserved, waiting for a protocol that will probably never arrive.
Checking What's on Port 349
To see if anything is listening on port 349 on your system:
Linux/Mac:
Windows:
You'll almost certainly find nothing. Port 349 is a ghost town.
Related Ports
Port 69 — TFTP (Trivial File Transfer Protocol), a much simpler file transfer protocol that actually succeeded
Port 989-990 — FTPS (FTP over SSL/TLS), another approach to secure file transfer
Frequently Asked Questions
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