Port 706: SILC — The chat protocol that saw the future

Port 706 was assigned to SILC (Secure Internet Live Conferencing), a protocol designed between 1996 and 1999 by Pekka Riikonen and first released publicly in summer 2000.¹

SILC looked like IRC—channels, nicknames, private messages, the familiar shape of Internet chat. But underneath, it was something different: a protocol where security wasn't a feature you could enable. It was the foundation you couldn't disable.²

What SILC did

SILC provided synchronous conferencing services: group channels, private messaging, file transfers. The kind of features every chat protocol offers. But every message, every piece of metadata, every connection was encrypted using strong cryptographic algorithms including AES and RSA.³

In an era when IRC sent everything in plaintext and encryption was something paranoid people worried about, SILC made a different assumption: all communication should be secure by default. You couldn't turn off the encryption. There was no "insecure mode" for easier debugging or lighter resource usage.

Security wasn't optional. It was the point.

The protocol that saw the future

SILC never became mainstream. IRC was entrenched. Proprietary chat systems dominated. The idea that every conversation needed military-grade encryption seemed excessive to most people in 2000.

But SILC's core assumption—that communications should be encrypted by default, that security should be mandatory rather than optional—eventually became the standard. Signal, WhatsApp, iMessage, modern web browsers with HTTPS Everywhere. The Internet finally caught up to what SILC understood in 1996.

Port 706 represents a road not taken. A protocol that saw where things were heading before most people understood the stakes. It's largely forgotten now, but its assumptions won the argument.

What range this port belongs to

Port 706 sits in the well-known port range (0-1023), which IANA reserves for system services and widely-used protocols. Being assigned a well-known port number meant SILC was recognized as a legitimate protocol worthy of standardized assignment, even if it never achieved widespread adoption.

Checking what's listening

To see if anything is using port 706 on your system:

# On Linux/Mac
sudo lsof -i :706
sudo netstat -tulpn | grep :706

# On Windows
netstat -ano | findstr :706

You're unlikely to find anything. SILC clients and servers are rare today, though the protocol technically still exists.

Why unassigned ports matter

Even though port 706 is assigned to SILC, it's effectively unused in most modern networks. These assigned-but-dormant ports are part of the Internet's history—markers of protocols that were tried, standardized, and either succeeded or quietly faded away.

They remind us that the Internet isn't inevitable. People designed protocols with different assumptions, made different bets about what would matter. Sometimes those bets were right decades too early.

Port 706 was one of those bets.