Port 600: Sun IPC server — A ghost from the distributed computing era

Port 600 is officially assigned to ipcserver (Sun IPC server), a legacy inter-process communication service from Sun Microsystems. Despite being a registered well-known port, you'll rarely find anything actually using it on modern systems.

What Range This Port Belongs To

Port 600 sits in the well-known ports range (0-1023), also called system ports. This range is reserved for services assigned by the Internet Assigned Numbers Authority (IANA) through formal procedures.¹

Ports in this range historically required root privileges to bind to on Unix-like systems—a security measure that assumed if you could bind to a system port, you were running trusted system software.

The Service: Sun IPC Server

The official IANA registry lists port 600 as assigned to "ipcserver" with the description "Sun IPC server."² This was part of Sun Microsystems' work on distributed computing and inter-process communication in the 1980s and early 1990s.

Sun Microsystems pioneered networked Unix systems during this era, creating foundational technologies like:

• Sun RPC (Remote Procedure Call) - the basis for network services³
• NFS (Network File System) - developed in 1984 for distributed file access⁴
• XDR (External Data Representation) - for platform-independent data encoding⁵

The Sun IPC server was part of this ecosystem, enabling processes on different machines to communicate. While Sun RPC became famous through NFS and used port 111 for the portmapper service, port 600 was registered for this specific IPC server implementation.

Why You Won't Find It Today

Port 600 is essentially unused on modern networks. Sun Microsystems' distributed computing architecture evolved, and many of their early protocols were replaced or superseded by newer technologies.

The port remains officially assigned—a historical marker in the IANA registry—but it's rare to encounter a system with anything actually listening on port 600.

How to Check What's Listening on Port 600

If you want to verify whether anything is using port 600 on your system, you have several options:

Using ss (modern Linux):

sudo ss -tulpn | grep ':600'

Using netstat (traditional):

sudo netstat -tulpn | grep ':600'

Using lsof (shows process details):

sudo lsof -i :600

The sudo is necessary because listing process information for ports requires root privileges on most systems.⁶

If nothing returns, port 600 is not in use—which is the expected result on nearly all modern systems.

Why Unassigned and Legacy Ports Matter

Port 600 illustrates an important aspect of Internet infrastructure: historical preservation.

The IANA registry doesn't just serve current needs—it maintains a record of what came before. Removing old assignments could cause conflicts if legacy systems are still running somewhere. Enterprise environments sometimes run decades-old software that still expects certain ports to be available.

More importantly, the registry prevents new services from accidentally claiming ports that might still be in use somewhere. Port 600 stays assigned to Sun IPC server even though Sun Microsystems was acquired by Oracle in 2010 and the service is obsolete.

This is the archaeology of the Internet. Every assigned port tells a story about what seemed important when it was registered. Some became essential infrastructure. Others, like port 600, became historical footnotes—officially assigned, rarely used, but preserved as a reminder of the networks that came before.

Related Ports

• Port 111 - SunRPC (portmapper), the widely-used Sun RPC service that became foundational to NFS⁷
• Port 2049 - NFS, Sun's Network File System that became a standard for distributed file access