Port 224: Masqdialer — The Modem-Sharing Protocol Time Forgot

Port 224 is assigned to masqdialer, a modem-sharing protocol for Linux systems. Both TCP and UDP. Registered to Charles Wright in the late 1990s.

What Masqdialer Does

Masqdialer is a client-server system that allows authorized users on a local network to control a dial-up modem connected to a Linux server. Instead of logging in via Telnet to manually dial out, clients send commands over port 224 to make the server establish or terminate dial-up connections.¹

The protocol was designed for IP Masquerade setups—where one Linux box with a modem provided Internet access to an entire LAN. Masqdialer gave everyone on that network the ability to trigger the dial-up connection without needing shell access to the server.

The Problem It Solved

In the late 1990s and early 2000s, dial-up was how most people connected to the Internet. If you had multiple computers but only one modem and one phone line, you needed a way to share that connection. Linux IP Masquerade let you route traffic, but someone still had to tell the modem to dial.

Masqdialer automated that. Any authorized client on the LAN could request a connection. The server would use standard tools like pppd and chat to dial out, establish the connection, and route traffic for the entire network.²

How It Works

The masqdialer daemon runs on the Linux server. Clients connect to port 224 (configurable) and send binary commands. The daemon authenticates the request and, if authorized, executes the dial-up script. The client can also request disconnection when done.

This was elegant for its time. You didn't need to give users shell access. You didn't need to teach them pppd syntax. You just gave them a client that spoke the masqdialer protocol, and they could dial out with a button press.

Why This Port Matters (And Doesn't)

Port 224 is a well-known port—assigned by IANA in the range reserved for system services (0-1023). This was appropriate when masqdialer was registered, because modem control was fundamental infrastructure.

But the world moved on. Broadband replaced dial-up. Always-on connections eliminated the need to manually dial out. The problem masqdialer solved simply stopped existing for most people.

Today, port 224 sits mostly unused. You won't find masqdialer running in modern networks. The protocol is a historical artifact, a reminder of how different the Internet was 25 years ago.

Security Considerations

If you somehow still run masqdialer, understand the risks:

• Authentication matters: The daemon must properly verify clients. If port 224 is exposed to untrusted networks, anyone could attempt to trigger dial-up connections or manipulate your modem.
• Binary protocol: Masqdialer uses a binary data stream. Vulnerabilities in parsing could be exploited if the software hasn't been maintained.
• Outdated software: Masqdialer was last actively developed in the early 2000s. Modern security standards didn't exist when this was written.

In practice, almost no one runs this anymore. If port 224 shows up in a scan of your network, it's worth investigating—but it's unlikely to actually be masqdialer unless you're maintaining legacy systems.

Checking What's On Port 224

To see if anything is listening on port 224 on your system:

Linux/Mac:

sudo lsof -i :224
sudo netstat -tuln | grep :224

Windows:

netstat -ano | findstr :224

If something is listening, investigate what process owns it. Legitimate masqdialer usage is extremely rare in 2026.

Related Ports

Port 224 doesn't have close relatives in the modem-sharing space—it's a niche protocol from a niche era. But conceptually, it sits alongside other remote administration protocols:

• Port 22 (SSH): Modern secure remote access, which replaced Telnet-based modem control
• Port 23 (Telnet): What people used before masqdialer to manually dial modems
• Port 3389 (RDP): Remote desktop protocol for Windows administration

The Bigger Picture

Port 224 is a memorial. It represents a specific moment in Internet history when connectivity was scarce, expensive, and required active management. Modem sharing was a real problem. People built real solutions.

And then the problem disappeared. Broadband arrived. Always-on connections became the norm. The entire concept of "dialing out" became something you had to explain to younger generations.

Port 224 still exists in the IANA registry because port assignments are permanent. But the protocol it was assigned for is effectively dead. The port remains, a bookmark in a chapter of Internet history that's finished.