Port 288: Unassigned — The Space Between Services

Port 288 exists, but nothing lives here. According to IANA's Service Name and Transport Protocol Port Number Registry, port 288 (both TCP and UDP) is officially "Unassigned."¹ It's part of a 12-port gap—288 through 299—that sits in the well-known range like a breath between sentences.

What the Well-Known Range Means

The well-known ports (0-1023) are the Internet's core infrastructure numbers. These ports require superuser privileges to bind on Unix-like systems. They're reserved for system processes that provide widely used network services—SSH on 22, HTTP on 80, HTTPS on 443.²

Port 288 has that same level of protection and significance as its assigned neighbors. The number is registered. It's protected. It just doesn't have a service yet.

The Neighbors

Port 287 carries K-BLOCK, an officially assigned service.³ Port 300 runs TACACSS.⁴ Between them: twelve empty numbers. Port 288 sits in the middle of that silence.

Why Gaps Exist

The gaps in the well-known range aren't accidents. They're the result of restraint and history:

Port conservation: Early Internet architects didn't fill every number. Some services got ranges they didn't strictly need. Others were never assigned at all.⁵

De-assignment policy: When a port is de-assigned, IANA doesn't reuse it until all unassigned ports in that range are gone. A de-assigned port becomes a protected gap—a space that remembers what used to be there.⁵

Reserved potential: Some numbers are kept open deliberately. Room for what hasn't been imagined yet. Room for the next protocol that will change everything.⁵

Port 288 has been unassigned since the registry began. It's not a retired number. It's a number that never got its calling.

No Unofficial Uses

Unlike some unassigned ports that get adopted by applications anyway, port 288 doesn't appear in any widely documented unofficial uses.⁶ It's genuinely quiet. If something is listening on port 288 on your system, it's either malicious or highly unusual.

How to Check What's Listening

On Linux or macOS:

# Check what's listening on port 288
sudo lsof -i :288
# or
sudo netstat -tulpn | grep :288

On Windows:

# Check what's listening on port 288
netstat -ano | findstr :288

If nothing returns, nothing is listening. That's normal for port 288.

Why This Matters

Unassigned ports are part of the Internet's architecture of possibility. Every assigned port represents a decision—someone saw a problem, designed a protocol, requested a number, and got it approved. Every unassigned port represents the opposite: the decision to wait, to leave space, to not assume we've already invented everything we'll need.

Port 288 is protected real estate in the most valuable range of port numbers. It's been waiting since the beginning. Maybe it will wait forever. Maybe tomorrow someone will submit an application to IANA with a protocol so essential, so fundamental, that it deserves to sit in the well-known range between K-BLOCK and TACACSS.

Until then, port 288 exists as pure potential. A number with all the weight of the well-known range and none of the responsibility. The space between services. The breath between sentences.

The Internet is as much defined by what it doesn't assign as what it does.