Port 1902: Fujitsu ICL Terminal Emulator Program B — a relic with a registered name

What This Port Is

Port 1902 is registered with IANA under the name fjicl-tep-b — Fujitsu ICL Terminal Emulator Program B — on both TCP and UDP.¹

ICL (International Computers Limited) was a British computer manufacturer that built mainframe and midrange systems throughout the 1970s and 1980s. Fujitsu acquired a controlling stake in 1990. The terminal emulator programs registered to ports 1901, 1902, and 1903 (programs A, B, and C respectively) served as network endpoints for connecting terminal sessions to ICL hardware.

That hardware is gone. The port remains on the registry.

What Range This Port Lives In

Port 1902 falls in the registered ports range (1024–49151). These ports require IANA registration but do not demand root or administrator privileges to open — unlike the well-known ports below 1024, which are reserved for operating system use.

Registered ports represent a deal: a vendor or protocol author claims a number, documents what they intend to use it for, and IANA records it. The claim has no enforcement mechanism. Nothing stops another application from using port 1902 for something entirely different.

Observed Uses in the Wild

One curious real-world sighting: Sony Bravia Android TVs have been observed making UDP connections on port 1902.² The cause is not officially documented by Sony. The leading theory in community forums is that it relates to Google Cloud Messaging or another background Android service — Android TV devices regularly reach out to various Google infrastructure endpoints, and port assignments in that range don't always correspond to the original IANA registrant.

This is common with registered ports from defunct products: the number gets recycled informally, and the IANA record becomes historical footnote rather than operational guide.

How to Check What's Listening on This Port

If you see traffic on port 1902 and want to know what's generating it:

On Linux or macOS:

# Show which process is listening on port 1902
ss -tlnp | grep 1902
# Or with lsof:
lsof -i :1902

On Windows:

netstat -ano | findstr :1902

The PID from netstat can be matched to a process name in Task Manager, or via:

tasklist /fi "PID eq <PID>"

To watch live traffic:

# Capture packets on port 1902 (requires root/sudo)
tcpdump -i any port 1902

Why Unassigned or Dormant Ports Matter

The registered port range contains thousands of entries for products that no longer ship, protocols that never gained adoption, and companies that no longer exist. Port 1902 is typical of this: legitimately registered, historically accurate, practically invisible.

This matters for two reasons. First, security scanners that see activity on port 1902 will flag it — correctly, since any unexpected listener on a registered-but-dormant port is worth investigating. Second, application developers who need a port number for internal use sometimes reach into this range without checking the registry, creating informal collisions that show up in firewall logs years later.

The port system is not a pristine catalog. It is a living record of every protocol someone thought worth registering, including many that outlasted the hardware they ran on.