RUTX11 Modbus

Summary

Modbus TCP Server

General

Data Sources

Modbus Serial Server

General

Data Sources

Modbus Registers

Get Parameters

Set Parameters

Modbus TCP Client

Requests Configuration

Alarms Configuration

Modbus Serial Client

General Status

Modbus Serial Device Configuration

RS Device Modbus Client Configuration

Modbus devices

Modbus device configuration

Requests Configuration

Modbus Client Alarms

MQTT Modbus Gateway

Serial Gateway Configuration

Request messages

• TCP:

 
0 <COOKIE> <IP_TYPE> <IP> <PORT> <TIMEOUT> <SERVER_ID> <MODBUS_FUNCTION> <FIRST_REGISTER> <REGISTER_COUNT/VALUES> <BROADCAST>

• Serial:

 
1 <COOKIE> <SERIAL_DEVICE_ID> <TIMEOUT> <SERVER_ID> <MODBUS_FUNCTION> <FIRST_REGISTER> <REGISTER_COUNT/VALUES> <BROADCAST>

• MODBUS TCP connection management messages:

 
2 <COOKIE> <CONNECTION_INDEX> <ACTION>

 
2 <COOKIE> <CONNECTION_INDEX> 0 <IP_TYPE> <IP> <PORT> <TIMEOUT>

• Cookie - a 64-bit unsigned integer in range [0..2⁶⁴-1]). A cookie is used in order to distinguish which response belongs to which request, each request and the corresponding response contain a matching cookie: a 64-bit unsigned integer.
• IP type - host IP address type. Possible values:
  • 0 - IPv4 address;
  • 1 - IPv6 address;
  • 2 - hostname that will be resolved to an IP address.
• IP - IP address of a Modbus TCP server. IPv6 must be presented in full form (e.g., 2001:0db8:0000:0000:0000:8a2e:0370:7334).
• Port - port number of the Modbus TCP server.
• Timeout - timeout for Modbus connection, in seconds. Range [1..999].
• Server ID - Modbus TCP server ID. Range [1..255].
• Modbus function - Modbus task type that will be executed. Possible values are:
  • 1 - read coils;
  • 2 - read input coils;
  • 3 - read holding registers;
  • 4 - read input registers;
  • 5 - set single coil;
  • 6 - write to a single holding register;
  • 15 - set multiple coils;
  • 16 - write to multiple holding registers.
• First register - number (not address) of the first register/coil/input (in range [1..65536]) from which the registers/coils/inputs will be read/written to.
• Register count/value - this value depends on the Modbus function:
  • 1 - coil count (in range [1..2000]); must not exceed the boundary (first coil number + coil count <= 65537);
  • 2 - input count (in range [1..2000]); must not exceed the boundary (first input number + input count <= 65537);
  • 3 - holding register count (in range [0..125]); must not exceed the boundary (first register number + holding register count <= 65537);
  • 4 - input register count (in range [0..125]); must not exceed the boundary (first register number + input register count <= 65537);
  • 5 - coil value (in range [0..1]);
  • 6 - holding register value (in range [0..65535]);
  • 15 - coil count (in range [1..1968]); must not exceed the boundary (first coil number + coil count <= 65537); and coil values separated with commas, without spaces (e.g., 1,2,3,654,21,789); there must be exactly as many values as specified (with coil count); each value must be in the range of [0..1].
  • 16 - register count (in range [1..123]); must not exceed the boundary (first register number + register count <= 65537); and register values separated with commas, without spaces (e.g., 1,2,3,654,21,789); there must be exactly as many values as specified (with register count); each value must be in the range of [0..65535].
• Broadcast - number used to identify that the broadcast is ON (in range [0..1]). Note: that broadcast flag is not ignored only when 5,15,6,16 Modbus functions are used.
  • 0 - if 0 or not specified - message will be sent only to a Modbus server, that matches the provided <SERVER_ID> in the message.
  • 1 - message will be sent to all available Modbus servers on the network.
• Serial device ID - a string used to identify a serial device. Must match with Device ID field in MQTT Gateway page Serial gateway configuration section.
• Connection index - a number used to identify a connection on which an action will be preformed (in range [0..7]).
• Action - a connection action. Possible values are:
  • 0 - OPEN. This will open a closed connection, reopen an already open connection with the same parameters or close an already open connection and open a new one with new parameters.
  • 1 - CLOSE. This will close an open connection and do nothing to the closed one.
  • 2 - STATUS. This will respond with either OK 1 for an open connection or OK 0 for a closed connection.

Response messages

<COOKIE> OK                              - 
for functions 6 and 16

<COOKIE> OK <VALUE> <VALUE> <VALUE>...   - 
for function 3, where <VALUE> <VALUE> <VALUE>... are read register values

<COOKIE> ERROR: ...                      - 
for failures, where ... is the error description

Examples

• Request:
  

  0 65432 0 192.168.1.1 502 5 1 6 206 1

• Response:
  

  65432 OK

• Request:
  

  0 65432 0 192.168.1.1 502 5 1 3 2 2

• Response:
  

  65432 OK 0 5590

• Request:
  

  mosquitto_pub -h 192.168.1.1 -p 1883 -t request -m "0 65432 0 192.168.1.1 502 5 1 3 2 2"

• Response:
  

  mosquitto_sub -h 192.168.1.1 -p 1883 -t response
  65432 OK 0 5590

JSON message structure

Request:
{
 "cookie":                  
Cookie - a 64-bit unsigned integer in range [0..264-1])

 "type":                    
Type - request type. Possible values:

                               
0 - TCP; (Serial)

                               
1 - Serial; (Serial)

                               
2 - Connection Control (Serial)

 "connection":              
Connection - Serial connection index. Optional if host is given.
 
 "host":                    
host - IPv4, IPv6, or FQDN address of server. Required if connection is not used or if type = 2 and action = open.

 
 "port":                    
Port - port number of the Modbus server.

 "timeout":                 
Timeout - timeout for Modbus connection, in seconds. Range [1..999].

 "server_id":               
Server ID - Modbus TCP/Serial server ID. Range [1..255].

 "device_id":               
Serial device ID - a string used to identify a serial device. Must match with Device ID field in MQTT Gateway page Serial gateway configuration section.

 
 "function":                
Modbus function - Modbus task type that will be executed. Possible values are:

                               
1 - read coils;

                               
2 - read input coils;

                               
3 - read holding registers;

                               
4 - read input registers;

                               
5 - set single coil;

                               
6 - write to a single holding register;

                               
15 - set multiple coils;

                               
16 - write to multiple holding registers.

 "register_number":         
First register - number (not address) of the first register/coil/input (in range [1..65536]) from which the registers/coils/inputs will be read/written to.

 
 "register_count":          
Register count/value - this value depends on the Modbus function.

 "coil_number":             
First coil address (for coil operations only)

 "coil_count":              
Number of coils to read (for coil operations only)

 "broadcast":               
Broadcast - number used to identify that the broadcast is ON (in range [0..1]). Note: that broadcast flag is not ignored only when 5,15,6,16 Modbus functions are used.

                               
0 - if 0 or not specified - message will be sent only to a Modbus server.

                               
1 - message will be sent to all available Modbus servers on the network.
   
 "value":                   
Single value to write (used with function 6). Must be from 0 to 65535

 "values":                  
Array of values (used with function 16). Comma-separated without spaces (e.g. 1,2,3,654,21,789). Number of values must match register count. Each value: 0–65535

 
 "action":                  
Action - a connection action. Possible values are:

                               
0 - OPEN. This will open a closed connection, reopen an already open connection with the same parameters or close an already open connection and open a new one with new parameters.

                               
1 - CLOSE. This will close an open connection and do nothing to the closed one.

                               
2 - STATUS. This will respond with either OK 1 for an open connection or OK 0 for a closed connection.

}
Response:
{
 "cookie":                  
Copied from request to identify it.

 "success":                 
True if the request succeeded, false otherwise.

 "data":                    
If success: can be a boolean or array of integers.

 "error":                   
If success is false: a string containing an error message.

}

Modbus TCP over Serial Gateway

Status

Modbus TCP over Serial Gateway Configuration

IP Filter

See also

• Monitoring via Modbus - detailed examples on how to use Modbus TCP