Port 887: ICL coNETion — A ghost from networking's past

Port 887 belongs to the well-known ports range (0-1023), the most restricted tier of port numbers. These ports are assigned by IANA and typically reserved for system services that need privileged access.

What Was ICL coNETion?

Port 887 is officially assigned to iclcnet-svinfo (ICL coNETion server info) for both TCP and UDP.¹ This was a proprietary networking service created by International Computers Limited (ICL), a British computer manufacturer that was major player in the 1970s-1990s before being absorbed into Fujitsu.²

The service provided server information exchange for ICL's coNETion networking environment. Like many proprietary protocols from that era, it needed its own dedicated port number to function.

Why This Port Matters (Even Though Nobody Uses It)

Port 887 represents something important about how the Internet evolved: early port assignments were permanent.

In the 1990s, when IANA was handing out well-known port numbers, the process was less rigorous than it is today. Companies could register ports for proprietary protocols. Once assigned, these reservations stuck around even after the technology became obsolete.

So port 887 sits there, officially reserved for a service that virtually nobody runs anymore. It's networking archaeology—a fossil layer showing what mattered in 1990s corporate IT.

Current Reality

In practice, port 887 is effectively unassigned. ICL coNETion server deployments are essentially extinct. If you see traffic on port 887 today, it's almost certainly:

• A legacy system that hasn't been updated in decades
• Someone repurposing the port for internal use (ignoring the official assignment)
• Malicious activity taking advantage of an unused port³

How to Check What's Listening

To see if anything on your system is using port 887:

Linux/Mac:

sudo lsof -i :887
netstat -an | grep 887

Windows:

netstat -ano | findstr :887

If you see something listening and you're not running 1990s ICL hardware, investigate it.

The Unassigned Port Problem

Port 887 illustrates a challenge in Internet infrastructure: what do you do with obsolete assignments?

The well-known ports range is valuable real estate. Only 1,024 numbers exist in this range, and they're running out. Meanwhile, hundreds of ports are reserved for services that no longer exist or were never widely deployed.

IANA can't easily reclaim these ports because:

• Someone, somewhere might still be using the old service
• Reassigning could break legacy systems
• The administrative overhead of proving a service is truly dead is enormous

So port 887 remains assigned to ICL coNETion server info, probably forever, even though the company that created it is long gone and the protocol is forgotten.

Related Ports

Port 886 was assigned to ICL coNETion locate server—another ghost from the same era.⁴