What This Port Is
Port 2878 is registered. IANA lists it as aap — the Multicast Address Allocation Protocol, assigned to both TCP and UDP. The registrant is Stephen Hanna, who co-authored the IETF draft with Mark Handley.
But the protocol it was reserved for never made it out of draft status.
The Protocol That Didn't Make It
In the late 1990s, the IETF was working on multicast infrastructure — the machinery that lets one server stream to thousands of recipients simultaneously. A piece of that infrastructure was multicast address allocation: when an application wants to broadcast, it needs a multicast address. If multiple servers hand out addresses independently, they might hand out the same one to two different streams.
AAP was meant to solve this. The Multicast Address Allocation Protocol let multiple Multicast Address Allocation Servers (MAASes) coordinate within a domain, using a claim-and-confirm mechanism to avoid collisions. Servers would send UDP messages to port 2878 and a reserved multicast address, announcing which address ranges they were using. If two servers claimed the same range, they'd detect the conflict and resolve it.
The working group was called MALLOC (Multicast Address ALLocation). The draft went through at least four revisions between 1999 and 2000. 1
Then it expired. It never became an RFC. The broader multicast deployment push stalled as the Internet shifted toward unicast delivery models (CDNs, peer-to-peer, eventually HTTP streaming). The elaborate infrastructure MALLOC was building for had fewer takers than expected.
Port 2878 stayed registered, waiting for a protocol that never shipped.
What You'll Find Here Today
Almost nothing. If you see traffic on port 2878, it is not AAP — AAP never deployed widely. It is more likely:
- Custom application traffic from software that happened to pick this port
- Scanning or probing from automated tools sweeping the registered port range
- Misconfiguration in a product that chose this port without checking IANA
Some security databases flag port 2878 as historically associated with malware activity. This is a generic warning applied to many obscure ports and should not be taken as evidence that anything on this port today is malicious.
How to Check What Is Listening
On Linux or macOS:
On Windows:
The process ID in the output will tell you exactly what is using the port. On Linux, lsof -i :2878 gives you the process name directly.
Why Ghost Ports Exist
The registered port range (1024–49151) has over 48,000 slots. IANA registers ports based on requests from protocol designers, but there is no mechanism to reclaim a port when a protocol fails to ship. AAP claimed 2878 in good faith; the protocol just never arrived.
These ghost registrations are not harmful — they are just artifacts of how the Internet standardization process works. Drafts get written. Working groups get chartered. Sometimes the technology lands. Sometimes the problem gets solved differently, or turns out to matter less than expected, and the draft quietly expires.
Port 2878 is a small monument to that: the effort of people who were trying to build multicast infrastructure for an Internet that went a different direction.
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