IEC 60870-5-104 Protocol

Full Master/Slave support with proper implementation in SerialMon v3.0!

IEC 60870-5-104 is the TCP/IP-based companion standard for telecontrol equipment and systems. It enables communication over standard network infrastructure between substations and control centers.

Protocol Overview

IEC 60870-5-104 uses the application layer of IEC 60870-5-101 over TCP/IP:

ISO/OSI Layer IEC 104 Layer
7. Application layer ASDU (same as IEC 101)
6. Presentation layer APCI (Application Protocol Control Information)
5. Session layer
4. Transport layer TCP (Port 2404)
3. Network layer IP
2. Data link layer Ethernet
1. Physical layer

APCI Frame Types

Type Name Description
I-Frame Information Contains ASDU with user data
S-Frame Supervisory Acknowledgement, flow control
U-Frame Unnumbered STARTDT, STOPDT, TESTFR commands

SerialMon Support

Proper implementation in SerialMon v3.0

Operating Modes

Mode Description
Monitor Passive network capture of IEC 104 traffic (port mirroring or PCAP files)
Master/CC Simulate a control center connecting to RTUs/IEDs
Slave/IED Simulate an RTU or IED accepting connections from control centers

Supported Features

  • All APCI frame types (I, S, U)
  • STARTDT/STOPDT/TESTFR handling
  • Sequence number management
  • General Interrogation (GI)
  • Time synchronization
  • Single and double commands
  • Measurement values (normalized, scaled, floating point)
  • Protocol validation with warnings for invalid messages
  • Signal acceptance marking for FAT/SAT testing
  • Quick command sending from tracking window
  • Multiple simultaneous connections

Connection Settings

Parameter Default Description
TCP Port 2404 Standard IEC 104 port
k (max unconfirmed I-frames) 12 Flow control parameter
w (latest ack threshold) 8 Acknowledgement threshold
t1 (connection timeout) 15s Response timeout
t2 (ack timeout) 10s Acknowledgement timeout
t3 (test timeout) 20s TESTFR timeout

Use Cases

  • SCADA Commissioning - Verify RTU/IED communication before go-live
  • Troubleshooting - Debug network communication issues
  • FAT/SAT Testing - Comprehensive acceptance testing with signal verification
  • Integration Testing - Test SCADA integration with simulated devices

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