IEC 61850 MMS Driver

Overview

IEC 61850 MMS (Manufacturing Message Specification) — the international standard for automation in power plants, substations, ESS, and wind farms. Runs on the full ISO stack (TPKT → COTP → ISO Session → ISO Presentation → ACSE → MMS). Uses an in-house Java ASN.1/BER implementation (no external dependencies).

Item	Value
`opc_type`	`IEC61850`
Implementation class	`plantpulse.driver.protocol.iec61850.IEC61850Driver`
Library	In-house Java implementation (no external dependencies, ASN.1 BER written in-house)
Inheritance	`BaseProtocolDriver`
read	OK (ReadRequest → AccessResult(MmsValue), polling)
write	OK (`isWriteSupported() = true`)
Security	None (IEC 62351 not implemented)
Default port	`102` (TCP)

Report (BRCB/URCB) support

In addition to polling reads, for each RCB specified in report-control-blocks the driver MMS-writes RptEna=true (plus the optional GI=true) on every connection, automatically restoring the report subscription. InformationReport (unsolicited push) messages are handled by the lastReportByVariable cache, and reads serve only cache entries fresher than the TTL (report-cache-ttl-ms) — on expiry it falls back to polling.

Class Structure (top-down)

TCP
 └ ISO TPKT (RFC 1006)             — Tpkt.java
   └ ISO COTP (Class 0)            — Cotp.java
     └ ISO Session                 — IsoSession.java
       └ ISO Presentation          — IsoPresentation.java
         └ ACSE                    — Acse.java
           └ MMS (ASN.1 BER)       — MmsPdu.java + Asn1.java + MmsAddress.java

Connection sequence (connect()): COTP CR → CC → Session CONNECT (encapsulating Presentation CP / ACSE AARQ / MMS Initiate-Request) → AARE → decode and validate MMS Initiate-Response. Constant DEFAULT_TPDU_SIZE = 0x0B (2048 bytes, as recommended by IEC 61850). Only a single session is used — transact() serializes transactions with synchronized and validates the response invokeID (mismatch = stale reject + socket invalidation).

OPC Registration Options

Key	Default	Description
`opc_agent_ip` / `opc_agent_port`	102 if port is 0	IED IP / port
`options.connect-timeout`	`5000` ms	TCP connect timeout
`options.read-timeout`	`5000` ms	read SO timeout
`options.enable-information-report`	`false`	Whether BRCB/URCB reporting is enabled
`options.report-control-blocks`	(none)	Comma-separated list of RCB references — e.g. `LD0/LLN0$BR$brcb01` (dot notation allowed)
`options.report-gi`	`true`	Performs a general interrogation (re-receive all current values) by writing `GI=true` immediately after RCB activation
`options.report-cache-ttl-ms`	`30000` ms	Freshness TTL for the report cache — falls back to polling on expiry. `<=0` disables expiry

Tag `plc_address` Format

MmsAddress accepts both LD/LN.DO.DA[$FC] notation and wire notation (LD/LN$FC$DO$DA). A slash (/) separates domain and item; a dot (.) is replaced with $ during wire conversion.

Notation	Meaning
`IED1Server/MMXU1.MX.A.phsA`	Domain IED1Server / Item MMXU1$MX$A$phsA
`IED1Server/MMXU1$MX$A$phsA`	Same in wire notation
`LD1/LLN0.Mod.stVal`	LD `LD1`, LN `LLN0`, DO `Mod`, DA `stVal`

The FC (Functional Constraint) is either stated explicitly with $FC or written by including its standard position ($MX / $ST, etc.).

Read / Write

read: buildReadRequest → transact() (synchronized) → parseReadResponse → returns AccessResult (MmsValue) as a string. An InformationReport arriving interleaved while awaiting a response is cached and the wait continues. Three consecutive read failures (READ_FAIL_STREAK_LIMIT) drop connected — triggering edge recovery (PLCRecovery).
write: isWriteSupported() = true. data_type → MmsValue mapping:

`data_type` alias	MmsValue
`boolean / bool`	`bool`
`integer / int / long / short / byte`	`integer` (parsed as long)
`unsigned / uint / ulong`	`unsigned`
`float / double / real / floating-point`	`floating`
`octet-string / octet / bytes`	`octet`
`visible-string / string / "" / varchar`	`visible`
`mms-string / utf8`	`mmsString`
Others	`visible` (fallback)

data-access-error codes are exposed as WriteResponse.errorCode.

Unsupported Areas

GOOSE / Sampled Values (multicast) — requires a separate raw-Ethernet stack.
SCL (.icd / .scd) parsing — no automatic data model discovery; entries must be made manually by the user.
IEC 62351-3/-6 — no TLS / authentication / integrity protection.

Fixture-level maturity

The ASN.1 BER utilities in this implementation are spec-accurate, but full wire-level interoperability with real IEDs is scheduled for a later phase. Thorough validation is recommended before production use.

References

IEC 61850-7-2 (ACSI), -8-1 (mapping to MMS), ISO 9506 (MMS). ASN.1 BER — ITU-T X.690.
Code: plantpulse-edge-driver/src/plantpulse/driver/protocol/iec61850/.

Overview​

Class Structure (top-down)​

OPC Registration Options​

Tag plc_address Format​

Read / Write​

Unsupported Areas​

References​