What This Port Is
Port 2455 is registered with IANA under the service name wago-io-system. Despite the search results on most port lookup sites calling it "unknown," it has a formal assignment — just not to anything most people running servers or browsers would ever encounter.
WAGO is a German manufacturer of industrial automation equipment. Their I/O System 750/753 series consists of modular programmable field controllers (PFCs) used in factories, process plants, shipbuilding, and building automation. Port 2455 is the default communication port used by these controllers for CODESYS V2, the programming and runtime environment that runs industrial control logic on the device. 1
In plain terms: somewhere in a building or plant, a small DIN-rail-mounted controller is reading sensor values — temperature, pressure, position — and triggering outputs. Port 2455 is how engineering software talks to that controller over Ethernet.
The Registered Port Range
Port 2455 falls in the registered port range (1024–49151), sometimes called "user ports." This range is where IANA tracks assignments for specific applications that aren't core Internet infrastructure. The well-known ports (0–1023) are reserved for foundational protocols — HTTP, DNS, SSH. Registered ports are for everything else that wanted a stable, documented number.
Being registered means an organization asked IANA to formally associate a port number with their software, creating a record that helps administrators, firewall teams, and security tools identify traffic. It doesn't mean the protocol is open or standardized in the way HTTP is. Many registered port services are proprietary, industrial, or enterprise-specific — invisible to most of the Internet.
What You'd Find If It's Open
If you see port 2455 listening on a machine, there are a few possibilities:
- A WAGO PFC controller — The device is running CODESYS V2 and accepting connections from WAGO's engineering tools or SCADA systems. Normal in an industrial environment. Unexpected anywhere else. 2
- Ephemeral port assignment — Operating systems sometimes use registered-range ports temporarily for outbound connections. If the port shows up briefly and disappears, it's likely this.
- Unknown application — Something else chose this port without knowing or caring about the IANA assignment.
How to Check What's Listening
On Linux/macOS:
On Windows:
The output will show the process ID. From there, check the process name to understand what's actually using it.
Why Unassigned-Looking Ports Matter
The registered port range contains thousands of entries like this one — formally claimed, but unknown to most administrators. When a port shows up in a firewall log or a vulnerability scan, the instinct is to look it up and get a clean answer. Ports like 2455 are a reminder that the Internet isn't just web servers and email. There's an entire layer of industrial, enterprise, and specialized software with its own port ecosystem, mostly invisible unless you're managing the systems that use it.
WAGO controllers running CODESYS aren't supposed to be Internet-accessible. When port 2455 appears on a public-facing scan, it's worth investigating immediately — it almost certainly shouldn't be there.
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