Port 485: Powerburst — The Cache That Tried to Save Dial-Up

What Port 485 Carries

Port 485 is registered with IANA for Powerburst (Air Soft Power Burst), a remote access acceleration protocol that operated over both TCP and UDP.¹² This protocol was designed in the 1990s to speed up file access over slow dial-up connections by caching files on the client side.

The Problem It Solved

In the mid-1990s, remote workers connected to corporate networks over dial-up modems. Every file request traveled across phone lines at 28.8 kbps or slower. Opening a Word document from a network share could take minutes. Saving a spreadsheet meant waiting while kilobytes crawled across copper wire.

Airsoft Inc., a Cupertino-based company, created Powerburst to make this less painful. The software cached files on the client machine and predicted what files you'd need next, fetching them in the background. When you opened a file you'd already accessed, it came from your local cache instead of traveling across the modem connection.³

How Powerburst Worked

Powerburst used a client-agent architecture:

• The client ran on the remote worker's machine, maintaining a cache of recently accessed files
• The agent ran on the file server, validating cached data and ensuring consistency across up to 64 concurrent clients³
• The protocol used look-ahead caching to predict future file requests based on usage patterns

When you accessed a file, the client checked its cache first. If the file existed locally, the agent verified it was still current. If the cached version was valid, no network transfer occurred. The company claimed response times improved 200-400%.⁴

The Technology That Disappeared

Powerburst worked with both Windows NT Server and Novell NetWare—the dominant corporate network operating systems of the era.³ In 1996, Shiva Corporation acquired Airsoft Inc. for approximately $65 million.⁵

Then broadband arrived. Cable modems and DSL made caching less critical. The pain Powerburst solved—waiting for files to crawl across phone lines—became a problem people no longer had. The protocol faded into obscurity.

Why This Port Matters

Port 485 sits in the well-known ports range (0-1023), meaning it was registered early enough to claim a spot in the Internet's most prestigious address space. But unlike its neighbors—ports carrying HTTP, SSH, and SMTP—this port carries almost nothing today.

It's a monument to a solved problem. A reminder that the Internet wasn't always fast. That people once built elaborate caching systems just to make opening a file feel bearable. That every era has its bottlenecks, and someone always tries to cache their way around them.

Checking Port 485

To see if anything is listening on port 485 on your system:

On Linux/Mac:

sudo lsof -i :485
# or
sudo netstat -tulpn | grep :485

On Windows:

netstat -ano | findstr :485

You probably won't find anything. Powerburst belongs to the era of screaming modems and "You've got mail." But the port number remains, registered in IANA's records, a fossil from when the Internet moved at the speed of phone lines.

Related Ports

• Port 80 (HTTP): The web traffic that Powerburst tried to accelerate
• Port 443 (HTTPS): Encrypted web traffic (which creates caching challenges)
• Port 3128 (Squid): A web proxy cache that solved similar problems at a different layer

The Truth About Port 485

This port represents the forgotten infrastructure of the dial-up era. Someone at Airsoft registered it with IANA, built software around it, and sold it to companies trying to make remote work bearable when "remote" meant a 28.8k modem.

The problem Powerburst solved doesn't exist anymore. We have bandwidth to waste now. But port 485 remains in the registry, a small memorial to the people who tried to make the slow Internet feel fast, one cached file at a time.