MBLogic
for an open world in automation
PollMB and PollWS
Overview:
PollMB is a simple Modbus/TCP command line client with the following features:
- It can read from and write to a Mobus/TCP server.
- It supports the most commonly used Modbus client functions.
- All parameters are configurable.
- It can poll repeatedly, to allow load testing of a server.
PollWS is a simple client which is similar to PollMB, but supports a Modbus-like web service.
Supported Modbus Functions:
The following Modbus functions are supported:
- 1 - Read Coils.
- 2 - Read Discrete Inputs.
- 3 - Read Holding Registers.
- 4 - Read Input Registers.
- 5 - Write Single Coil.
- 6 - Write Single Holding Register.
- 15 - Write Multiple Coils.
- 16 - Write Multiple Holding Registers.
Command Line Parameters:
Address, function codes, and other values are specified by means of command line parameters. If a parameter is omitted, its default value is used. The parameters are:
Ethernet address
| Parameter | Description | Default Value |
|---|---|---|
| -h | Host name of the ModbusTCP server1 | localhost |
| -p | Port number of the ModbusTCP server | 502 (PollMB) 80 (PollWS) |
| -t | Receive time-out in seconds2 | 60 (mininum = 1) |
1 Note: -h (host). For PollMB, this is the IP address or domain name.
For PollWS, this is the URL to the web service, including IP address and any
additional URL path.
2 Note: -t (time-out) is accepted by PollWS, but is ignored.
Modbus parameters
| Parameter | Description | Default Value |
|---|---|---|
| -f | Function | 1 |
| -a | Address (Modbus memory) | 0 |
| -q | Quantity of addresses | 1 |
| -u | Unit ID | 1 |
Polling parameters
| Parameter | Description | Default Value |
|---|---|---|
| -r | Repeats. Number of times to perform the poll | 1 |
| -y | Delay time between repeats in milliseconds1 | 1 |
| -d | Data to send to the server | 0000 |
| -s | Silent mode. 'Y' or 'y' will suppress displaying data | 'no' |
1Note: Actual delay time is affected by the resolution of the operating system process scheduler.
Sending Data:
- For functions 1, 2, 3, or 4, any data specified is ignored.
- For functions 5, 6, 15, or 16, data must be specified.
- For function 5 (write single coil), data must be either 0 or 1.
- For function 15 (write multiple coils), data must be 0 and 1 characters, in multiples of 8 characters. E.g. 00111010.
- For functions 6 and 16 (write single or multiple registers), data must be in hexadecimal with 4 characters per register. Hexadecimal values a to f may be in lower or upper case. E.g. 23aD
Return Codes:
The following command line return codes are defined:
| Return Code | Description |
|---|---|
| 0 | No errors |
| 2 | Bad command line |
| 3 | Program was terminated from keyboard |
| 4 | Invalid data for modbus function |
| 5 | Error communicating with host |
| 6 | Invalid modbus parameters |
Using PollMB:
PollMB is normally used from the command line. For Linux, the syntax is:
Example:
./pollmb.py <parameters>
For Microsoft Windows, the syntax is:
Example:
python pollmb.py <parameters>
A typical example is:
Example:Example:
./pollmb.py -h 192.168.10.1 -p 8502 -t 10 -f 16 -a 6789 -q 2 -u 45 -d 0123abcd
Using PollWS:
PollWS uses a similar syntax. For Linux, the syntax is:
Example:
./pollws.py <parameters>
For Microsoft Windows, the syntax is:
Example:
python pollws.py <parameters>
A typical example is:
Example:Example:
./pollws.py -h 192.168.10.1/modbus -p 8502 -t 10 -f 16 -a 6789 -q 2 -u 45 -d 0123abcd
Polling performance measurement:
- When used to measure polling performance, silent mode should be enabled.
- When more than one repeat is specified, extra information is displayed after polling is completed. This includes elapsed time, number of data elements transfered, and the data transfer rate.
- When trying to measure maximum speed a large enough number of polls should be specified to allow measurement over several (e.g. 5 to 10) seconds in order to get an accurate reading.