Port 1593: MainSoft License Manager — A registered port in the vast middle range

Port 1593 is officially assigned to mainsoft-lm (MainSoft License Manager) for both TCP and UDP protocols.¹ Unless you're running MainSoft software, this port is almost certainly closed on your system right now.

The Registered Port Range

Port 1593 lives in the registered ports range (1024-49151). This is the middle territory of the port number space:

• Well-known ports (0-1023): Reserved for common services like HTTP, SSH, DNS
• Registered ports (1024-49151): Assigned by IANA to specific applications upon request
• Dynamic/ephemeral ports (49152-65535): Temporary ports used for client-side connections

There are 48,128 registered ports. Companies and organizations apply to IANA to claim a specific number for their software. MainSoft applied for and received port 1593. Most of these assignments sit dormant—waiting for software that may never be installed on any given machine.

What Is MainSoft License Manager?

MainSoft License Manager is a software licensing service. License managers are the bouncers of the software world—they track how many copies of an application are running, who's authorized to use it, and whether the license has expired.

When software checks its license, it often communicates with a license server over the network. Port 1593 is MainSoft's designated door for that conversation.

Why This Port Matters (Even If You Never Use It)

The registered port range exists to prevent collisions. Without it, every software vendor would pick their own port number at random, and conflicts would be constant. Two applications trying to listen on the same port? One of them fails.

IANA's registry is a namespace—a way to coordinate 48,000+ different intentions so they don't crash into each other. Port 1593 is MainSoft's slot in that coordination system.

Most registered ports are like P.O. boxes that never receive mail. They exist in the registry, but they're not open on your machine unless the specific software that uses them is installed and running.

Security Considerations

If you find port 1593 listening on your system and you're not running MainSoft software, investigate:

# Linux/macOS - See what's listening on port 1593
sudo lsof -i :1593
netstat -tlnp | grep 1593

# Windows - See what's listening on port 1593
netstat -ano | findstr :1593

An unexpected open port can indicate:

• Software you forgot you installed
• Malware masquerading as a legitimate service
• A misconfigured application that bound to the wrong port

Like any port in the registered range, 1593 should only be open if you deliberately installed software that uses it.¹

The Reality of Port Numbers

There are 65,535 possible TCP ports. 65,535 possible UDP ports. That's 131,070 doors a packet could knock on.

Most of them are closed. Most of the registered ones have never been used on your machine and never will be. Port 1593 is probably one of them.

But it exists in the registry so that if someone, somewhere, installs MainSoft software, the license manager knows where to listen. And nothing else will be sitting in that spot.

This is how the Internet scales: endless coordination, most of it for things that never happen on any given machine, but might happen somewhere.