Port 2823: CQG Net/LAN — The trading floor's private door

Port 2823 is registered with IANA for CQG Net/LAN — the client-server communication protocol for CQG, a financial technology company providing market data, technical analysis, and electronic trading tools to brokers, traders, and exchanges worldwide.¹

If you see traffic on port 2823, someone is running CQG trading software.

What CQG Does

CQG has been in financial data since 1980 — before most of the modern Internet existed. They consolidate real-time and historical market data from more than 100 exchanges across the Americas, Europe, Asia, and Australia, and pipe it to traders who need to make decisions in milliseconds.²

Their software — CQG Integrated Client, CQG Trader, and related tools — connects to CQG's servers over TCP. Port 2823 is one of two endpoints where those servers listen. Port 443 (HTTPS) is the other, used as a fallback when firewalls block 2823.³

In 2025, Broadridge Financial Solutions acquired CQG.⁴

What Runs on This Port

All CQG client-to-server communication is TCP, client-initiated only. The server never opens connections to the client. What flows through:

• Market data and news — unencrypted, prioritized for speed
• Login transactions — encrypted
• Order routing — SSL encrypted

The asymmetry is intentional: market data latency matters more than confidentiality (prices are public). Orders and credentials are a different story.³

Is It in the Right Range?

Port 2823 sits in the registered port range (1024–49151). IANA maintains this range for applications that need a stable, predictable port number — software that says "my clients know to find me here." Registered ports don't get the same automatic firewall trust that well-known ports (0–1023) carry, but they're not ephemeral either. They're permanent addresses for permanent services.¹

CQG's registration here is straightforward: trading software needs a consistent port so that firewall administrators at brokerages and trading firms can open exactly the right hole and nothing else.

How to Check What's Listening

If you see activity on 2823 and want to confirm what's there:

# macOS / Linux
sudo lsof -i :2823
sudo ss -tlnp | grep 2823

# Windows
netstat -ano | findstr :2823

On a trading workstation running CQG, you'll see an established TCP connection to a CQG server. On any other machine, port 2823 should be closed and silent.

Why Unassigned Neighbors Matter

Most ports in the registered range have no official owner. They exist as open slots — available for whatever application needs a stable number and submits the right paperwork to IANA. Port 2823 has an owner. Its neighbors almost certainly don't. That's normal. The registered range has 48,128 slots and far fewer legitimate applications. The empty ones aren't unused so much as unclaimed, filling up only temporarily with dynamic traffic or staying silent entirely.