Protocol Tools
81 protocol tools articles on the Voltrus blog.
Modbus Poll vs Modscan vs Modbus Slave: Which Master Tool to Use
Modbus Poll, Modscan, and Modbus Slave compared. Platform support, RTU vs TCP, master and simulator modes, pricing, and which Modbus master tool fits your workflow in 2026.
Read articleModbus TCP vs PROFINET: Choosing the Right Industrial Ethernet
Modbus TCP vs PROFINET compared. Real-time determinism, device discovery, configuration effort, vendor ecosystem, and when to use each industrial Ethernet protocol.
Read articleHow to Read Modbus Holding Registers (FC03): A Practical Walkthrough
How to read Modbus holding registers with function code 03. Slave ID, start address, quantity, the FC03 frame, 16-bit byte order, and 32-bit scaling explained.
Read articleHow to Write Modbus Registers: FC06, FC16, and Coils FC05/FC15
How to write Modbus registers and coils. FC06 write single register, FC16 write multiple, FC05/FC15 coils. Frame layout, exception codes, and safe write practice.
Read articleModbus RTU to TCP Gateway: Bridge Serial Devices onto Ethernet
Modbus RTU to TCP gateway explained. Why bridge RS-485 serial devices onto Ethernet, how a gateway routes TCP requests to RTU slaves, latency, hardware vs software gateways.
Read articleEtherNet/IP vs PROFINET: Rockwell vs Siemens Industrial Ethernet
EtherNet/IP vs PROFINET compared. Rockwell/Allen-Bradley vs Siemens ecosystems, CIP vs PROFINET IO, real-time classes, device description, and which to choose.
Read articleHow to Read Allen-Bradley Tags Without RSLinx or FactoryTalk
Read Allen-Bradley ControlLogix and CompactLogix tags without RSLinx, FactoryTalk, or Windows. How the ENIP session and CIP tag services work, and how to browse and read tags anywhere.
Read articleEtherNet/IP ListIdentity: How Device Discovery Works (UDP 44818)
EtherNet/IP ListIdentity discovery explained. How a broadcast on UDP 44818 finds every CIP device, what the Identity reply contains, and how to browse devices on macOS.
Read articleCIP Explicit vs Implicit Messaging: When to Use Each
CIP explicit vs implicit messaging compared. Explicit (TCP 44818, request-response, tag reads) vs implicit (UDP 2222, cyclic I/O, RPI). Use cases, overhead, and when each wins.
Read articleEtherNet/IP Port 44818 Explained: TCP, UDP 2222, and Firewall Rules
EtherNet/IP port 44818 explained. TCP 44818 for explicit messaging, UDP 2222 for cyclic I/O, UDP 44818 for ListIdentity discovery. Firewall rules and security.
Read articleDNP3 vs Modbus for SCADA: Which Protocol for Utilities
DNP3 vs Modbus for SCADA compared. Event-driven reporting, timestamps, class polling, multi-drop vs point-to-point, and which fits utilities and water/wastewater.
Read articleDNP3 vs IEC 60870-5-104: Power Utility Protocols Compared
DNP3 vs IEC 60870-5-104 compared. The two dominant power-utility SCADA protocols. Addressing, transport, event model, region, and which to choose for substations.
Read articleHow to Simulate a DNP3 Outstation for Testing
How to simulate a DNP3 outstation. Why you need a simulator, configuring addressing and points, generating Class 0/1/2/3 events, and testing a DNP3 master without field hardware.
Read articleDNP3 Class 0, 1, 2, 3 Explained: Event Polling Strategy
DNP3 Class 0, 1, 2, 3 explained. Class 0 is a full snapshot; Classes 1-3 are prioritized event backlogs. How utility masters poll by class to retrieve only what changed.
Read articleDNP3 Select-Before-Operate (SBO): Safe Control Outputs
DNP3 Select-Before-Operate explained. Why SBO guards critical controls, how the select-then-operate two-step works, select timeouts, and direct operate for non-critical points.
Read articleOPC UA vs OPC Classic (DA): Why the Upgrade Matters
OPC UA vs OPC Classic (DA) compared. Platform-independent transport, built-in security, rich information model, and why migrating from COM-based OPC DA to OPC UA matters.
Read articleOPC UA Information Model: Nodes, Objects, and the Address Space
OPC UA information model explained. Nodes, objects, variables, type system, the address space, references, and companion specifications. How UA self-describes data.
Read articleOPC UA Security: Certificates, Encryption, and Auth Setup
OPC UA security explained. Security modes (None, Sign, SignAndEncrypt), security policies, X.509 certificates, mutual authentication, trust lists, and secure setup.
Read articleHow to Browse an OPC UA Server Address Space
How to browse an OPC UA server address space. Connect, get endpoints, open a session, browse nodes by reference, find variables, and read values on any platform.
Read articleOPC UA Subscriptions and Monitored Items: Subscribe to Variable Changes
OPC UA subscriptions and monitored items explained. Publishing interval, sampling, data-change filters, and why subscribe beats poll for live monitoring.
Read articleSiemens S7-1200 vs S7-1500: Which PLC for Your Project
Siemens S7-1200 vs S7-1500 compared. Performance, memory, I/O count, motion, safety, PROFINET, price, and which Siemens PLC fits small machines vs large process lines.
Read articleS7 Protocol vs OPC UA for Siemens PLCs: Direct or Standardized
S7 protocol vs OPC UA for Siemens PLCs compared. Native direct access vs the cross-vendor standard, performance, security, setup, and when to use each.
Read articleHow to Read a Siemens S7 Data Block (DB) Over the Network
How to read a Siemens S7 data block. DB number and offset addressing, data types, the rack/slot connection, enabling PUT/GET, and reading S7-1200/1500 DBs.
Read articleHow to Enable PUT/GET on S7-1200/1500 (and Why Siemens Disables It)
How to enable PUT/GET on Siemens S7-1200/1500. Why Siemens disables it by default, the TIA Portal steps, the security trade-off, and safer alternatives like OPC UA.
Read articleSiemens S7 vs Modbus TCP: Native PLC Access vs Universal Register
Siemens S7 vs Modbus TCP compared. Native data-block access vs universal register addressing, typed vs flat data, where each wins, and how Siemens sites run both.
Read articleBLE GATT Services and Characteristics Explained: How Every BLE Device Is Structured
The GATT data model end to end: ATT vs GATT, the Profile, Service, Characteristic, Descriptor hierarchy, UUID formats, characteristic properties, the CCCD, ATT operations, and a full byte-level walk-through of the Heart Rate Service.
Read articleiBeacon vs Eddystone: BLE Beacon Formats Compared
Byte-level layout of iBeacon and Eddystone (UID, URL, TLM frames), how proximity is estimated from RSSI and why it is noisy, plus how to decode both formats from raw advertising packets on macOS.
Read articleBLE Pairing and Bonding: Security Explained
Pairing vs bonding, LE Legacy vs LE Secure Connections (ECDH P-256), the four association models, the STK/LTK key hierarchy, AES-CCM encryption, IRK-based privacy, Security Mode 1 levels, and how to debug auth failures on macOS.
Read articleModbus RTU Over Serial: How It Works on RS-485
A byte-level breakdown of Modbus RTU on RS-485: frame structure, CRC-16 with polynomial 0xA001, function codes, 3.5-character inter-frame timing, and a worked FC03 request/response you can read off the wire.
Read articleRS-485 Termination and Biasing: Why Your Serial Bus Is Unreliable
Why RS-485 buses produce CRC errors and garbage bytes: differential signalling, 120-ohm end termination, fail-safe bias resistor math, unit-load counting, and daisy-chain-only topology.
Read articleMQTT Topic Design: Best Practices for Naming and Wildcards
MQTT topic naming rules, forward-slash hierarchy, the + and # wildcards, shared subscriptions, ACL security, and the anti-patterns that bite teams in production.
Read articleMQTT vs HTTP for IoT: Which Protocol Should You Use
MQTT vs HTTP for IoT — publish/subscribe vs request/response, 2-byte headers vs hundreds, push vs poll, QoS guarantees, and when to use each protocol.
Read articleOPC UA Companion Specifications: How UA Models Real Industries
How OPC Foundation collaborations with industry bodies (VDMA, PLCopen, VDW, BACnet) add typed, domain-specific information models so multi-vendor equipment interoperates without per-vendor register maps.
Read articleOPC UA vs Modbus TCP: Which Industrial Protocol to Choose
Modbus TCP and OPC UA compared on data model, security, discovery, transport, scalability, and best-fit use cases — plus the gateway-aggregation pattern most plants actually run.
Read articlePROFINET vs S7 Communication: What's the Difference
PROFINET IO and S7 communication are not competing protocols — they coexist on every Siemens controller. PN-IO is the deterministic fieldbus for cyclic I/O; S7 is the acyclic read/write protocol over TCP port 102. Ports, RFC 1006, RT/IRT timing, GSDML, and macOS tooling explained.
Read articleMQTT vs Direct Database Writes from IoT Devices: Why the Broker Wins
Why IoT devices that INSERT directly to Postgres, MySQL, or SQL Server break at scale — connection limits, schema coupling, no offline buffering, credential sprawl — and why an MQTT broker feeding a single ingest bridge is the architecture that survives a field fleet.
Read articleBLE Advertising Packets Explained: How Devices Broadcast Without Connecting
BLE advertising packets explained: the 31-byte payload, AD structures, flags, UUIDs, manufacturer data, scan response, and how to decode raw advertising data on macOS.
Read articleMQTT Keep Alive Explained: What It Is, How to Tune It, and Why Clients Disconnect
MQTT keep alive explained: the CONNECT packet field, the 1.5x timeout rule, PINGREQ/PINGRESP, how brokers detect dead clients, and how to choose the right interval for IoT devices.
Read articleEtherNet/IP RPI Explained: Requested Packet Interval, CIP I/O, and How to Tune It
EtherNet/IP RPI (Requested Packet Interval) explained: the timing of CIP implicit I/O, how RPI differs from the CIP connection timeout, and how to choose and tune RPI values for Allen-Bradley PLCs.
Read articleModbus 32-Bit Integer Data Types: Registers, Byte Order, and Scaling Explained
How Modbus handles 32-bit integers: two registers per value, word order (high word first vs low word first), signed vs unsigned, register pairs, and scaling examples for energy meters and drives.
Read articleVoltrus Gateway vs Kepware: A Cross-Platform OPC Gateway Alternative
Kepware is the default — a Windows-only, licensed OPC server with per-tag pricing. Voltrus Gateway is a cross-platform, self-hosted Rust binary exposing one typed gRPC API across six protocols, one-time per host. An honest feature-by-feature comparison.
Read articleOne Typed gRPC API for Every Industrial Protocol
Why one typed gRPC surface beats a separate client for Modbus, OPC UA, EtherNet/IP, S7, DNP3, and BACnet. Type-preserving values, server-streamed subscriptions, and a single canonical implementation.
Read articleModbus, OPC UA & EtherNet/IP in One Binary: Unifying Six Protocols
How one Rust binary drives Modbus TCP, OPC UA, EtherNet/IP (CIP), Siemens S7, DNP3, and BACnet/IP behind a single API. The mt-* engines, read/write/subscribe parity, and why protocol bugs get fixed once.
Read articleModbus Function Codes Explained: FC01–FC06, FC15, FC16 (2026 Reference)
Every standard Modbus function code explained: FC01 read coils, FC03 read holding registers, FC06 write single register, FC16 write multiple. Request/response frame layout, byte order, and when to use each code.
Read articleModbus Addressing Explained: PLC Address vs Protocol Address (No More Off-By-One)
Why Modbus holding register 40001 is protocol address 0. The PLC address vs protocol address off-by-one confusion, the four address ranges, and how to convert between them.
Read articleModbus Exception Codes Explained: Illegal Function, Data, Address (2026 Troubleshooting)
Modbus exception codes 01–08 decoded: Illegal Function, Illegal Data Address, Illegal Data Value, Slave Device Failure. What each exception means, why your master gets it, and how to fix the request.
Read articleBACnet Objects and Properties: The Object Model Explained
BACnet models every data point as an object with typed properties (Present-Value, Units, Status-Flags). This self-description enables discovery — no external register map needed.
Read articleOPC-UA vs MQTT for Industrial IoT: Which Should You Choose
OPC-UA for rich plant-floor integration and SCADA; MQTT for lightweight multi-site telemetry. Data models, security, bandwidth, and when each protocol wins.
Read articleModbus Float Byte Order Explained: ABCD, DCBA, BADC, CDAB
A 32-bit Modbus float spans two registers and every vendor picks a different byte order. Why your 230 V reading shows as 0.003, and how to cycle the four conventions to fix it.
Read articleSiemens S7 Rack and Slot Addressing: How PLC Routing Works
S7 connections need the right rack and slot (S7-1200/1500: rack 0 slot 0; S7-300: rack 0 slot 2). Get it wrong and you get a connection-refused — here is why and how to fix it.
Read articleMQTT Retained Messages and Last Will: Explained with Examples
Retained messages give new subscribers instant state; Last Will publishes on ungraceful disconnect for offline detection. Concrete topic and payload examples included.
Read articleModbus TCP Security Risks: Why It Is Not Safe and How to Protect It
Modbus TCP has no authentication, encryption, or integrity — anyone on the network can read and write every register. Segment, firewall, and tunnel it; never expose TCP/502.
Read articleBACnet Explorer vs YABE: The Native macOS YABE Alternative
YABE is the free default — and a Windows .NET app that breaks on Apple Silicon and fails BACnet/IP discovery. Here is the honest feature-by-feature comparison and why a native $29.99 YABE alternative wins for Mac commissioning.
Read articleBACnet vs Modbus for Building Automation (2026): Protocol Comparison
BACnet vs Modbus for building automation. Compare data models, discovery, scalability, and HVAC integration. When to use each protocol and how to test on macOS.
Read articleEtherNet/IP and CIP Protocol Explained (2026): Complete Guide
EtherNet/IP and CIP protocol explained. Understand explicit vs implicit messaging, CIP data types, Allen-Bradley tag addressing, and how EtherNet/IP compares to Modbus TCP and OPC UA.
Read articleBest Modbus Simulator in 2026: Free and Paid Tools Compared
Need to test Modbus devices without hardware? Compare 7 Modbus simulators: Modbus Poll, Modbus Slave, diagslave, and more. Covers macOS, Windows, Linux. Free download links included.
Read articleModbus Poll Tool: How to Read and Write Registers on macOS (2026)
A complete guide to Modbus poll tools: what they do, how they work, function codes FC01-FC06, and how to read/write Modbus registers on macOS with a native poll tool. TCP + RTU support.
Read articleModbus RTU Troubleshooting Guide: CRC Errors, Timeouts, and Wiring
Fix Modbus RTU communication errors. Step-by-step troubleshooting for CRC errors, timeouts, and wiring problems. How to read Modbus RTU frames and diagnose RS485 bus issues.
Read articleModbus TCP Tool for macOS: Test and Debug Devices Without Windows (2026)
Need a Modbus TCP tool on macOS? MacTools Modbus Poll is a native Mac app for testing and debugging Modbus TCP devices. Read/write registers, simulate slaves, verify register maps.
Read articleMQTT Sparkplug B Explained: Industrial IoT Protocol Guide (2026)
MQTT Sparkplug B explained for industrial automation. Understand topics, payloads, birth/death certificates, data types, and how Sparkplug B compares to basic MQTT.
Read articleTIA Portal on Mac (2026): Why It Doesn't Work & What to Use Instead
TIA Portal doesn't run on macOS. Here's why, what your options are (Parallels, Remote Desktop), and the native macOS alternative for PLC programming.
Read articleUSB to RS485 on macOS (2026): Adapter Guide for Apple Silicon
Complete guide to USB-RS485 adapters on macOS. FTDI, CH340, CP2102 driver installation for Apple Silicon. Troubleshooting port detection, wiring RS485 devices.
Read articleWhat Is Modbus? The Protocol That Runs Industrial Automation
Modbus explained for engineers: how it works, why it's still dominant after 50 years, and the difference between Modbus RTU, TCP, and ASCII.
Read articleModbus RTU vs TCP: Which Variant Should You Use?
Modbus RTU and Modbus TCP use the same protocol but different transports. Frame format, speed, device limits, and when to choose each variant.
Read articleModbus Register Types Explained: Coils, Discrete Inputs, Holding Registers, Input Registers
The four Modbus data types and their function codes. How to read coils (FC01), write registers (FC06/FC16), and avoid common addressing mistakes.
Read articleS7 Communication Protocol Guide: Memory Areas, Addressing, and Data Types
How the Siemens S7 protocol accesses PLC memory. Data blocks, inputs, outputs, markers, timers, counters. Rack/slot addressing and data type mapping.
Read articleRS-232 vs RS-485 vs RS-422: Serial Communication Protocols Compared
UART, RS-232, RS-485, and RS-422 explained. Distance limits, device count, noise immunity, and which serial standard your industrial equipment uses.
Read articleMQTT QoS Levels Explained: When to Use QoS 0, 1, or 2
MQTT QoS 0, 1, and 2 explained with practical examples. At-most-once, at-least-once, exactly-once delivery for IoT and industrial systems.
Read articleIndustrial Protocol Comparison: Modbus vs OPC UA vs MQTT vs S7
Side-by-side comparison of the four most common industrial protocols. Data models, security, speed, vendor lock-in, and when to use each one.
Read articleBACnet Explorer for macOS: Browse Building Automation Devices Without Windows
Discover, monitor, and control BACnet/IP devices on macOS. Browse objects, read and write properties, and inspect real-time values across BACnet networks. No Windows, no costly BACnet software.
Read articleEtherNet/IP Explorer for macOS: Connect to Allen-Bradley PLCs Without RSLinx
Browse tags, read and write controller data on Allen-Bradley ControlLogix and CompactLogix PLCs over EtherNet/IP. Native macOS app — no RSLinx, no FactoryTalk, no Windows.
Read articleDNP3 Explorer for macOS: Monitor SCADA Outstations on Utilities and Water Systems
Monitor DNP3 outstations, read binary/analog points, and scan Class 0/1/2/3 events on macOS. Built for utilities and water/wastewater using DNP3 protocol.
Read articleOPC-UA Explorer for macOS: Browse OPC-UA Servers Without UA Expert
Browse OPC-UA address spaces, subscribe to variable changes, and read/write node attributes on macOS. Connect to any OPC-UA server without Windows tools.
Read articleModbus Poll for macOS: A Native Alternative That Actually Works
Looking for Modbus Poll on macOS? MacTools Modbus Poll is a native Mac app for reading and writing Modbus TCP and RTU registers. Master + slave simulator with device templates. $29.99 one-time.
Read articleBest Modbus Simulator for macOS (2026): PM5560, SMA Inverter, and More
Modbus simulator with real device templates. Simulate Schneider PM5560 power meter, SMA solar inverter, ABB analyzer on macOS. No Parallels, no Windows.
Read articleSchneider PM5560 Modbus Register Map and Simulator
Complete PM5560 Modbus register map with addresses for voltage, current, power, power factor, frequency, and energy. Includes a PM5560 simulator for macOS.
Read articleSerial Terminal for macOS: Alternatives to screen, minicom, and CoolTerm
Best serial terminal apps for macOS in 2026. Compare screen, minicom, CoolTerm, Serial by Decisive Tactics, and MacTools. Hex view, protocol analysis, USB-RS485.
Read articleMQTT Broker on macOS: Run One Without Homebrew or Terminal
How to run an MQTT broker on macOS without Homebrew, Terminal, or mosquitto. Native MQTT broker and client with GUI for macOS.
Read articleConnect to Siemens S7-1200/1500 from macOS Without TIA Portal
Read and write Siemens S7 PLC data blocks from macOS. No TIA Portal, no Parallels, no Windows. Native S7 communication tool for Mac.
Read articleBLE Debugging on macOS: nRF Connect Alternatives That Actually Work
BLE debugging tools for macOS when nRF Connect won't install. Scan, connect, browse GATT services, read/write characteristics on macOS.
Read articleModbus TCP vs OPC-UA: What System Integrators Actually Need to Know
Modbus is simple. OPC-UA is complex. Here is the honest comparison: when each makes sense, and why the middleware gap matters.
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