Port 34: Unassigned — The Empty Room in the Well-Known Range

Port 34 has no officially assigned service. It sits in the well-known port range (0 through 1023), the most regulated territory in the port numbering system, and yet no protocol has ever formally claimed it.

The Well-Known Range

Ports 0 through 1023 are called "well-known" or "system" ports. They are assigned through IETF Review or IESG Approval, the most rigorous process in the port assignment system¹. On Unix-like systems, binding to a port in this range requires root privileges, a deliberate security boundary that prevents unprivileged programs from impersonating critical services.

This is the range where the Internet's foundational protocols live: HTTP on port 80, HTTPS on port 443, SSH on port 22, DNS on port 53. Getting a number here means your protocol matters to the infrastructure of the network itself.

Port 34 sits between port 33 (Display Support Protocol) and port 35 (any private printer server)². Both neighbors have assignments. Port 34 does not.

The "Remote File" Question

Some third-party port databases associate port 34 with a "Remote File" (RF) protocol³. This appears in various online port lookup tools, but the IANA Service Name and Transport Protocol Port Number Registry, the authoritative source, lists port 34 as Unassigned for both TCP and UDP².

If a Remote File protocol ever used port 34, it either predates the formal registry process or was never officially registered. The protocol itself, whatever it was, has been entirely superseded by FTP, SFTP, SCP, and SMB. No modern system uses it.

Why Unassigned Ports Exist

The well-known range contains 1,024 ports. Not all of them are assigned, and that is by design. The assignment process is deliberately conservative. Jon Postel, who maintained the original port number registry by hand from the early days of the ARPANET, understood that scarcity creates discipline⁴. You do not hand out well-known port numbers to every protocol that asks. Some must prove they deserve infrastructure-level status.

The result: gaps in the numbering. Ports that were never claimed, or were once informally used and never formalized. Port 34 is one of these. It is not reserved, not deprecated, not retired. It simply was never assigned.

Security Considerations

If you see traffic on port 34, pay attention. Because no legitimate service is assigned to this port, any activity on it is unexpected by definition. While port 34 does not appear on widely published trojan port lists⁵, that is almost beside the point. Unexpected traffic on unassigned ports is one of the clearest signals that something on your network deserves investigation.

How to Check What Is Listening on Port 34

Linux:

sudo ss -tlnp | grep ':34 '
sudo lsof -i :34

macOS:

sudo lsof -i :34
netstat -an | grep '\.34 '

Windows:

netstat -an | findstr ":34 "
Get-NetTCPConnection -LocalPort 34

If any process is listening on port 34 and you did not put it there, investigate.