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IEC 62056 is a set of standards for electricity metering data exchange by International Electrotechnical Commission.

The IEC 62056 standards are the international standard versions of the DLMS/COSEM specification.

DLMS or Device Language Message Specification (originally Distribution Line Message Specification),[1] is the suite of standards developed and maintained by the DLMS User Association (DLMS UA) and has been adopted by the IEC TC13 WG14 into the IEC 62056 series of standards. The DLMS User Association maintains a D Type liaison with IEC TC13 WG14 responsible for international standards for meter data exchange and establishing the IEC 62056 series. In this role, the DLMS UA provides maintenance, registration and compliance certification services for IEC 62056 DLMS/COSEM.

COSEM or Companion Specification for Energy Metering, includes a set of specifications that defines the transport and application layers of the DLMS protocol. The DLMS User Association defines the protocols into a set of four specification documents namely Green Book, Yellow Book, Blue Book and White Book. The Blue Book describes the COSEM meter object model and the OBIS object identification system, the Green Book describes the architecture and protocols, the Yellow Book treats all the questions concerning conformance testing, the White Book contains the glossary of terms. If a product passes the conformance test specified in the Yellow Book, then a certification of DLMS/COSEM compliance is issued by the DLMS UA.

The IEC TC13 WG14 groups the DLMS specifications under the common heading: "Electricity metering data exchange - The DLMS/COSEM suite". DLMS/COSEM protocol is not specific to electricity metering, it is also used for gas, water and heat metering.


DLMS Master


DLMS (Device Language Message Specification) is a suite of standards developed and maintained by the DLMS User Association. COSEM (Companion Specification for Energy Metering) includes a set of specifications that define the transport and application layers of the DLMS protocol.

In DLMS/COSEM all the data in electronic utility meters and devices are represented by means of mapping them to appropriate classes and related attribute values.

Objects are identified with the help of OBIS (Object Identification System) codes (as per IEC 62056-61).

The DLMS driver allows only for readout and displaying only numeric values of DLMS object data fields. Connection via TCP (HDLC or WRAPPER) or serial (RS232/RS485) port are supported.

The setup of the DLMS driver consists of communication and tag configuration. Protocol specific parameters (except for DLMS/IEC handshake mode) apply for both serial and IP connections.


Devices section

serialnumber, server_address and id define the meter addressing parameters. Either serialnumber (meter serial number) or a combination of server_address (physical server address) and id (logical server address) is used. If a serial number is provided, physical and logical server addresses are ignored.

Before configuring the Device section it is best to first check the connection parameters with a 3rd party DLMS utility.

master_address defines the client address. This usually depends on the authentication used. Most meters support 16 for no authentication.
type defines the object referencing. SN should be used for short name referencing and LN for logical name referencing.

mode defines the communications mode. If IEC is used along with comms settings for serial readout, the connection is initiated as per IEC 62056-21, at the default initial baud rate (300 7E1). DLMS-HDLC shall be used for HDLC connections via IP. DLMS-WRAPPER is also supported for IP connections. The default setting is DLMS-HDLC.

timeout_ms defines the reply timeout for telegrams both via serial and TCP.

auth and password define the authentication mode and password. This can be set to None, or other authentication variant (see table below), depending on the mode configured and supported by the particular meter.
ip and port define the IP address and TCP port for DLMS communication via IP.

Connection parameters are device specific and can differ between makes, models and utility companies. For initial connection settings please refer to the configuration of the particular meter.

When ip and port are configured, any serial port settings are ignored and connection is initiated only via IP.

Device configuration parameters for DLMS meters acquisition:

Parameter Description Type Default value Example

Meter serial number

unsigned long 0 1122334455

Meter physical server address

unsigned long 0 1600

Meter logical server address

unsigned long 0 1


Client address

integer 16 1

Meter object referencing: SN - short referencing, LN - logical referencing

string SN LN

Comms mode: IEC handshake (for serial only), DLMS-HDLC or DLMS-WRAPPER (for IP)


Timeout in milliseconds

integer 2500 1500

Authentication: None, Low, High, HighMd5, HighSha1, HighSha256, HighGmac HighEcdsa

string None Low

Password for authentication

string n/a MyPass123

IP address

string n/a

TCP port

integer n/a 4059
Signals section

The tag_job defines the tag job. A list of comma-separated OBIS codes (or a single OBIS) should be used. Attribute indexes for objects of types register and extended register are selected automatically. Any other object types should include the attribute index in the form of OBIS:index.
tag_job_todo defines the job sub-job. This field should contain an OBIS code from within the list of the tag_job.

DLMS configuration parameters creating signals:

Parameter Description Type Default value Example

Tag job as single or multiple comma separated OBIS codes

string n/a



tag sub job

string n/a