Configuration

Enabled

Enables or disables the IEC 60870-5-104 server instance. When disabled, the server will not be initialized or accept any client connections.

Server

• Network interface: Specifies the IP address of the network interface to which the server should bind. Use 0.0.0.0 to listen on all available interfaces.

• TCP Port: Specifies the TCP port on which the server will listen.

• Max. connections: Specifies the maximum number of simultaneous client connections that the server will accept. Exceeding this limit will result in new connection attempts being rejected. The maximum configurable value is 100 connections.

• Allowed IP addresses: Specifies the maximum number of simultaneous client connections that the server will accept. Exceeding this limit will result in new connection attempts being rejected. The maximum configurable value is 100 connections.

Timing

• T1: Specifies the maximum time (in milliseconds) the server will wait for an acknowledgement (ACK) after transmitting an APDU (Application Protocol Data Unit). If no ACK is received within this timeout, the APDU is considered lost or corrupted, and the server will retransmit it. Default value: 15000 ms.
  Example: If T1 is set to 15000 ms, the server expects an ACK from the client within 15 seconds after sending data. If the ACK is not received within this period, the server assumes a communication failure and retries the transmission. This mechanism helps maintain reliable communication in case of network delays or packet loss.

• T2: The T2 parameter, also known as the APDU acknowledgement timeout, defines the maximum time the server can wait before sending a supervisory APDU to acknowledge a received APDU. The default setting is 10000 ms.
  Example: With a T2 timeout of 10000 milliseconds, a server receiving APDUs from the client will wait for up to 10000 milliseconds before sending an acknowledgement. This allows the server to bundle multiple acknowledgements into a single message, increasing communication efficiency. The server will send the acknowledgement sooner if the maximum number of unacknowledged APDUs (defined by the W parameter) is reached before the T2 timeout expires.

• T3: The T3 parameter, also known as the idle timeout, defines the maximum amount of time a communication link can remain idle (without any APDU exchange) before a TEST APDU frame is transmitted to verify the connection's integrity. If the client does not respond to this test frame within the T1 timeout period, the server will assume the connection is lost and will terminate it. The default setting is 20000 ms.
  Example: With a timeout of 20000 milliseconds, a test frame will be sent to the client if no APDUs are exchanged within this timeframe. The receipt of any APDUs will reset this timer, ensuring that communication remains active and the connection is not dropped due to inactivity.

Protocol settings

• K: The K parameter defines the maximum number of unconfirmed APDUs that can be transmitted before waiting for an acknowledgement. This value acts as a flow control mechanism for the TCP connection. The default setting is 12.
  Example: With a K value of 12, the server can transmit up to 12 APDUs to the client before it must receive a confirmation. If the client sends an acknowledgement before this limit is reached, the counter is reset, and the server can continue sending. If the limit is reached, the server must pause transmission and wait for a supervisory APDU from the client.

• W: The W parameter defines the maximum number of APDUs that can be received from a remote station (client) before the server is required to send an acknowledgement. This acts as a receiver-side flow control. The default setting is 8.
  Example: With a W value of 8, the server will hold off on sending an acknowledgement to the client until it has received 8 unacknowledged APDUs or the T2 timeout period has elapsed. At that point, the server will transmit a supervisory APDU to acknowledge all received APDUs, which helps optimize network traffic.

Enabled

Toggles the active state of this IEC 60870-5-104 slave/outstation instance. When disabled, the slave/outstation will not respond to any client requests.

Common address of ASDU

The Common address of ASDU (COA) uniquely identifies this device within the IEC 60870-5-104 network. This value is included in all outgoing APDUs.  

Valid range: 1 to 65534.

Event timestamp mode

Specifies the timestamp format used when the device sends event messages. This setting determines which ASDU (Application Service Data Unit) types are used for event transmission. The available modes are:

• None: Events are sent without a timestamp. Uses ASDU types that do not include a time tag, such as:

  • M_SP_NA_1 – Single-point information  

  • M_DP_NA_1 – Double-point information  

  • M_ME_NA_1 – Measured value, normalized value  

  • M_BO_NA_1 – Bitstring of 32 bits.

• Short time (Cp24Time2a): 24-bit timestamp format including minute, second, and millisecond. This is a short time tag; the receiving system must infer the date and hour. Uses ASDU types such as:

  • M_SP_TA_1 – Single-point information with 24 bits short-time tag.

  • M_DP_TA_1 – Double-point information with 24 bits short-time tag.

  • M_ME_TA_1 – Measured value, normalized value with 24 bits short time tag.  

  • M_BO_TA_1 – Bitstring of 32 bits with 24 bits short time tag.

• Long time (Cp56Time2a): 56-bit timestamp format with full date and time (year, month, day, hour, minute, second, millisecond). This long-time tag provides complete and precise time information. Uses ASDU types such as:

  • M_SP_TB_1 – Single-point information with 56 bits long-time tag.

  • M_DP_TB_1 – Double-point information with 56 bits long-time tag.

  • M_ME_TD_1 – Measured value, normalized value with 56 bits long-time tag.

  • M_BO_TB_1 – Bitstring of 32 bits with 56 bits long-time tag.

Tag

Select the source tag that this information object will expose through the IEC 60870-5-104 server. The data type of the selected tag must be compatible with the configured ASDU type to maintain data integrity.

Data type

Specifies the IEC 60870-5-104 data type used to encode and transmit the value of this information object. The selected type must match the source tag's data type to maintain data integrity.

• Available data types for reading (server → client):

  • Single point: 1-bit Boolean value (e.g., ON/OFF, OPEN/CLOSED). Corresponds to ASDU types such as M_SP_NA_1.

  • Double point: 2-bit discrete state (e.g., ON, OFF, Intermediate, Error). Corresponds to ASDU types such as M_DP_NA_1.

  • Normalized value: 16-bit signed integer representing an analog value in a normalized range from -1.0 to +1.0. Corresponds to ASDU types such as M_ME_NA_1.

  • Scaled value: 16-bit signed integer representing an analog value, ranging from -32768 to +32767. Corresponds to ASDU types such as M_ME_NB_1.

  • Bit string: 32-bit unsigned value for flags or binary patterns. Corresponds to ASDU types such as M_BO_NA_1.

  • Floating point: 32-bit IEEE 754 floating-point analog value. Corresponds to ASDU types such as M_ME_NC_1.

• Available data types for writing (client → server):

  • Single point command: 1-bit Boolean command (e.g., ON/OFF). Corresponds to ASDU types such as C_SC_NA_1.

  • Double-point command: 2-bit discrete command for state changes. Corresponds to ASDU types such as C_DC_NA_1.

  • Normalized value command: 16-bit integer command to set an analog value. Corresponds to ASDU types such as C_SE_NA_1.

  • Scaled value command: 16-bit integer command with scaling applied. Corresponds to ASDU types such as C_SE_NB_1.

  • Bit string command: 32-bit command to write raw binary data. Corresponds to ASDU types such as C_BO_NA_1.

  • Floating point command: 32-bit IEEE 754 floating-point command. Corresponds to ASDU types such as C_SE_NC_1.

Information object address

The Information Object Address (IOA) serves to uniquely identify each data point or information object within a device or station. The address must be a unique integer for each information object associated with a given data type. The range of possible IOA values is from 1 to 16777215 (3 octets).

Interrogation group (used for monitoring or accessing information objects)

Associates this information object with a specific interrogation group. When a client issues an interrogation request for a group, the server will respond with all information objects assigned to that group. This feature makes data handling more efficient by letting clients request specific subsets of data instead of retrieving all data points.

Available options:

• None: The information object is not assigned to any specific interrogation group (1-16). It will be included in the General Interrogation (a full data refresh request) and will also be sent as a spontaneous event whenever its value changes.

• Interrogation groups 1 through 16.: Assigns the object to a specific group (1–16). The server will return the object when that particular group is interrogated by the client. Additionally, it will be included in the General Interrogation (a full data refresh request) and will also be sent as a spontaneous event whenever its value changes.