Modbus protocol framework

1. Modbus RTU over TCP
2. Modbus Slave mode (Modbus Server)
3. Modbus Master mode (Modbus Client)
4. Rest server for read/write Modbus Data
5. gRPC service (Server/Client)
6. Dump Modbus packets
7. Function:

• Read Coil Status (0x1)
• Read Discrete Inputs (0x2)
• Read Holding Registers (0x3)
• Read Input Registers (0x4)
• Force Single Coil (0x5)
• Preset Single Register (0x6)
• Force Multiple Coils (0xF)
• Preset Multiple Registers (0x10)

go get github.com/soldatov-s/go-modbus

Next, build and run the examples:

• mb-server.go for an Modbus RTU over TCP server example
• mb-client.go for an Modbus RTU over TCP client example

• /coils - Coils (GET and PUT)
• /d_in - Discrete Inputs (only GET)
• /hold_reg - Holding Registers (GET and PUT)
• /in_reg - Input Registers (only GET)

Example Read Holding Registers:

curl -X GET -i 'http://localhost:8000/hold_reg?addr=0&cnt=5'

Example Write Holding Registers:

curl -X POST -i http://localhost:8000/hold_reg --data '{
"addr": 0,
"data": [77, 11]
}'

More documentation about Modbus is available on the

• Wiki
• Modbus Technical Specifications