Port 8: Unassigned — The Gap Between Echo and Oblivion

Port 8 is unassigned. No protocol runs here by right. No RFC defines it. No service claims it. In the IANA Service Name and Transport Protocol Port Number Registry, port 8 appears as a blank line: Unassigned.¹

It has been this way since the beginning.

The Neighbors

To understand what port 8 isn't, look at what surrounds it.

Port 7 is Echo. Send it bytes, it sends them back. Jon Postel defined the Echo protocol in RFC 347, dated May 30, 1972.² It exists so you can ask the network, "Are you there?" and hear your own voice come back.

Port 9 is Discard. Send it bytes, it throws them away. Postel defined Discard in RFC 348, written the same day.³ It exists so you can pour data into the void and test whether the pipe works, even if no one is listening at the other end.

Port 8 sits between them. Reflection on one side, oblivion on the other. It does neither.

What "Unassigned" Means

Port 8 falls in the System Ports range (0 through 1023), also called the Well-Known Ports. These are governed by IANA and, per RFC 6335, require "IETF Review" or "IESG Approval" to assign.⁴ On most operating systems, binding to any port in this range requires root or administrator privileges.

Being unassigned does not mean unused. It means no standard protocol has been allocated here. Any software can listen on port 8 if it has the right permissions. Some do. The SpeedGuide port database associates port 8 with a trojan called "Ping Attack," though this is obscure and not widely documented.⁵

In practice, if you see something listening on port 8, it is either custom software, a test configuration, or something worth investigating.

Why Empty Ports Exist

When Postel first catalogued the assigned numbers in RFC 739 in November 1977, ports were already sparse.² Some numbers had protocols. Many did not. The early Internet did not assign ports sequentially. Protocols were placed where they made sense, or where someone happened to request a number. Gaps were natural.

Port 8 was never requested. Over 45 years, through dozens of revisions to the Assigned Numbers documents (RFC 739, 750, 776, 820, 900, 923, 943, 960, 990, 1010, 1060, 1340, and finally 1700 in 1994), port 8 remained blank.⁶ Not deprecated, not reserved, not retired. Simply never claimed.

This is not a failure. The port numbering system has 65,535 slots. Not all of them need to be full. The gaps are part of the design. They leave room for the future, for protocols that do not yet exist, for problems no one has thought to solve.

How to Check What Is Listening on Port 8

On Linux:

sudo ss -tlnp | grep ':8 '
sudo lsof -i :8

On macOS:

sudo lsof -i :8
netstat -an | grep '\.8 '

On Windows:

netstat -ano | findstr ":8 "

With nmap (remote scan):

nmap -p 8 target-host

If anything responds, you have found custom software. There is no standard service that should be listening here.