MB-Forwarder

Features

• 🔄 Protocol Forwarding: Support for forwarding between Modbus TCP and RTU protocols
• 🌐 Multi-Server Support: Connect to multiple Modbus slave devices simultaneously
• 📡 Complete Function Code Support: Support for all standard Modbus function codes
• 🔧 Flexible Configuration: Flexible connection parameter configuration via YAML files
• 📊 Connection Monitoring: Automatic connection status monitoring with reconnection support
• 🚀 Cross-Platform: Support for Linux, Windows, macOS and other platforms

Supported Modbus Function Codes

Function Code	Name	Description
01	Read Coils	Read single or multiple coil states
02	Read Discrete Inputs	Read single or multiple discrete input states
03	Read Holding Registers	Read single or multiple holding register values
04	Read Input Registers	Read single or multiple input register values
05	Write Single Coil	Write single coil state
06	Write Single Register	Write single register value
15	Write Multiple Coils	Write multiple coil states
16	Write Multiple Registers	Write multiple register values

System Requirements

• Go 1.24.0 or higher
• Linux/Windows/macOS operating system

Installation

Build from Source

# Clone repository
git clone https://github.com/TwoMental/mb-forwarder.git
cd mb-forwarder

# Run
make run

Download Pre-built Version

Download pre-built versions suitable for your system from the Releases page.

Configuration

Configuration File Format

Create a config.yaml file, following the format in config.yaml.example:

# Listen port
listen_port: 1602

# Server configuration
servers:
  # Slave device 1 (TCP connection)
  1:
    conn_type: "tcp"        # Connection type: "tcp" or "rtu"
    slave_id: 1             # Slave device ID (1-255)
    addr: "192.168.1.100"   # TCP address or serial device name
    port: 502               # TCP port (required for TCP connections)
    timeout: 5              # Connection timeout in seconds
  
  # Slave device 2 (RTU connection)
  2:
    conn_type: "rtu"        # RTU connection
    slave_id: 1           
    addr: "/dev/ttyUSB0"    # Serial device name
    baud_rate: 9600         # Baud rate
    data_bits: 8            # Data bits
    stop_bits: 1            # Stop bits
    parity: "N"             # Parity: "N"(none), "E"(even), "O"(odd)
    timeout: 3

Configuration Parameters

Global Configuration

• listen_port: Port number for the forwarder to listen on, default 1602

Server Configuration

• conn_type: Connection type, supports "tcp" or "rtu"
• slave_id: Slave device ID, range 1-255
• addr: Connection address
  • TCP: IP address
  • RTU: Serial device name (e.g., /dev/ttyUSB0, COM1)
• port: TCP port number (required only for TCP connections)
• baud_rate: Baud rate (required only for RTU connections)
• data_bits: Data bits (required only for RTU connections)
• stop_bits: Stop bits (required only for RTU connections)
• parity: Parity (required only for RTU connections)
• timeout: Connection timeout in seconds

Usage

Start the Forwarder

# Start with configuration file
./mb-forwarder -config config.yaml

# Or specify configuration file path
./mb-forwarder -config /path/to/config.yaml

How It Works

1. Startup Phase: After startup, the forwarder creates a Modbus server and listens on the specified port
2. Connection Initialization: Creates connections to various slave devices according to configuration
3. Request Processing: Receives client requests, parses them, and forwards them to corresponding slave devices
4. Response Return: Returns slave device responses to clients
5. Connection Monitoring: Regularly checks connection status and records connection anomalies

Log Output

The forwarder outputs detailed runtime logs:

2024/01/01 12:00:00 modbus forwarder listening on 0.0.0.0:1602
2024/01/01 12:00:00 initialized slave 1 connection (tcp)
2024/01/01 12:00:00 initialized slave 2 connection (rtu)
2024/01/01 12:00:00 modbus forwarder started with 2 servers
2024/01/01 12:00:00 Modbus forwarder started, press Ctrl+C to stop...

Troubleshooting

Common Issues

1. Connection Failures

   • Check if slave devices are online
   • Verify IP addresses and port numbers
   • Confirm firewall settings

2. Serial Connection Issues

   • Check serial device permissions
   • Verify serial parameter settings
   • Confirm device driver installation

3. Timeout Errors

   • Increase timeout configuration values
   • Check network latency
   • Verify slave device response times

Performance Optimization

• Use connection pools to manage connections
• Set appropriate timeout values
• Monitor connection status and handle anomalies promptly
• Adjust buffer sizes based on network environment

Contributing

Issues and Pull Requests are welcome!

License

This project is licensed under the LICENSE license.

Contact

• Project URL: https://github.com/TwoMental/mb-forwarder
• Issue Reports: Issues