Category: Listener#

The Listener category documents the services and ports that are open on an object and waiting for incoming connections. It is a multi-value category -- any number of listener entries can be created to represent all active network services.

Usage#

Typical use cases:

• Firewall documentation: Each listener entry corresponds to an inbound firewall rule: protocol, port, and bound IP address define what should be reachable from outside. Together with the gateway field (firewall object), this creates a complete mapping from service to firewall rule.
• Security audits and hardening: A report on all listener entries immediately shows which ports are open on which servers. Unexpected entries -- such as a MySQL listener on port 3306 bound to 0.0.0.0 instead of 127.0.0.1 -- stand out immediately during evaluation and can be hardened in a targeted manner.
• Service inventory and service mapping: Through the link via the Opened by application field, it becomes visible which software occupies which port. This is indispensable for change management: If a port is changed, you immediately know which application is affected.
• Dependency analysis: Listeners are the connection target for the Network Connections category. When other objects have established connections to a listener, this reveals the dependencies -- crucial before maintenance work or migrations.

Fields#

Layer 3/4 protocol#

The transport protocol -- typically TCP or UDP. Dialog+ field, so additional protocols such as SCTP or DCCP can be added as needed. The choice of protocol is relevant for correctly mapping firewall rules, as these usually differentiate between TCP and UDP.

Layer 5-7 protocol#

The application protocol running on this port: HTTP, HTTPS, SSH, SMTP, DNS, LDAP, etc. This field gives the port entry semantic meaning -- port 443 alone says little, but port 443 with protocol HTTPS makes the purpose immediately clear. Also a Dialog+ field.

(Bind) IP address#

The IP address that the service is bound to. The selection is restricted to IP addresses that are already created in the Host Address category of the object. Typical values:

• A specific IP (e.g. 192.168.1.10) -- the service is only reachable through this interface
• 0.0.0.0 -- the service listens on all IPv4 interfaces

Port range (from/to)#

The port or port range that the service listens on. For a single port, both values are identical (e.g. 22 / 22 for SSH). Port ranges occur with:

• FTP passive mode: e.g. ports 30000--31000
• RPC services: dynamically assigned port ranges
• Application-specific ranges: e.g. in microservice architectures

Opened by application#

Link to an application object that creates this listener. Here you select, for example, the object "Apache HTTP Server" or "PostgreSQL." This link closes the gap between network and application documentation: You can see not only that port 5432 is open, but also that PostgreSQL is responsible for it.

Gateway#

Link to a firewall or router object through which incoming traffic is routed. Together with protocol, port, and bind address, this creates a complete data record that corresponds to a firewall allow rule.

Description#

Free text for additional information: firewall rule ID (e.g. "FW-2025-087"), configuration notes (e.g. "only reachable from management VLAN"), ticket numbers for the network share, or TLS configuration details.

Technical Reference#

Fields (API Reference)#

API Examples#

Create Entry#

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{
    "jsonrpc": "2.0",
    "method": "cmdb.category.save",
    "params": {
        "apikey": "your-api-key",
        "object": 1042,
        "category": "C__CATG__NET_LISTENER",
        "data": {
            "protocol": "TCP",
            "protocol_layer_5": "HTTPS",
            "ip_address": "192.168.1.10",
            "port_from": 443,
            "port_to": 443,
            "opened_by": "Apache HTTP Server",
            "gateway": 1003,
            "description": "Productions-web server, TLS 1.3, Firewall-Regel FW-2025-087"
        }
    },
    "id": 1
}

Read Entries#

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{
    "jsonrpc": "2.0",
    "method": "cmdb.category.read",
    "params": {
        "apikey": "your-api-key",
        "object": 1042,
        "category": "C__CATG__NET_LISTENER"
    },
    "id": 2
}

Update Entry#

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{
    "jsonrpc": "2.0",
    "method": "cmdb.category.save",
    "params": {
        "apikey": "your-api-key",
        "object": 1042,
        "category": "C__CATG__NET_LISTENER",
        "entry": 5,
        "data": {
            "protocol_layer_5": "HTTP/2",
            "description": "Upgrade auf HTTP/2, Change CR-2026-003, alte Firewall-Regel beibehalten"
        }
    },
    "id": 3
}