Port 2419: Attachmate S2S — A Registered Port from Enterprise Computing's Past

What This Port Is

Port 2419 is registered with IANA as Attachmate S2S — a server-to-server protocol belonging to Attachmate Corporation, an enterprise software company that built its business connecting personal computers to IBM mainframe systems.¹

It sits in the registered port range (1024–49151), meaning a company formally claimed it from IANA for a specific application. Unlike the well-known ports below 1024, registered ports don't require root privileges to open, and their assignments aren't enforced — they're just official reservations.

What Attachmate Was

Attachmate was founded in 1982 and became a dominant force in terminal emulation — software that made modern computers speak the language of IBM mainframes. When a bank employee on a Windows PC needed to query a 40-year-old System z host, Attachmate's products (EXTRA!, Reflection, InfoConnect) made that possible by emulating IBM 3270 terminals.²

The S2S designation almost certainly refers to server-to-server communication within Attachmate's gateway architecture — how Attachmate servers coordinated with each other when routing connections between terminal users and mainframe hosts.

Attachmate absorbed several competitors over the decades — WRQ, NetManage, Novell's network software division — before being acquired by Micro Focus in 2014.³ Micro Focus was then acquired by OpenText in 2023. The Attachmate brand no longer exists as an independent entity.

Current Status

If you see traffic on port 2419, you're almost certainly looking at one of two things:

1. Legacy enterprise infrastructure running old Attachmate products — large banks, insurers, and government agencies that still connect to mainframes and haven't updated in years
2. Random application use by software that needed an available port and picked one from the registered range

There are no known active malware families or significant security tools that specifically target port 2419. Security databases note it has been flagged in the past, but this is a historical artifact with no current known threat.⁴

Check What's Listening

If port 2419 is open on a system you manage and you don't run Attachmate software, find out what claimed it:

Linux / macOS:

# Show the process listening on port 2419
sudo ss -tlnp | grep 2419
# or
sudo lsof -i :2419

Windows:

netstat -ano | findstr :2419

The PID in the last column can be looked up in Task Manager to identify the process.

Why Unassigned-in-Practice Ports Exist

The registered port space was designed as a coordination mechanism — a way for software vendors to claim a port number so their products wouldn't collide with each other. When a company registers a port and later disappears, the registration typically stays in place indefinitely. IANA doesn't reclaim ports on behalf of defunct companies.

This means the registered range is full of entries like port 2419: technically claimed, practically dormant. The Internet's port namespace accumulates history the way old cities accumulate street names from businesses that closed decades ago.