Quickstart
Modpoll is a tool for communication with Modbus devices, so ideally it makes more sense if you have a real modbus device on hand for the following test, but it is OK if you don’t, we have deployed a virtual Modbus TCP device on cloud at modsim.topmaker.net:502, the code is available in my another project modsim, let’s start expoloring modpoll tool with the virtual device modsim.
Test with modsim
modsim is a very simple Modbus TCP device simulator deployed on cloud, it populates the first 100 registers for each type of Coil / Discrete input / Input register / Holding register,
modsim register configuration Object type
Access
Size
Address Space
Coil
Read-write
1 bit
1-100
Discrete Input
Read-only
1 bit
10001-10100
Input Register
Read-only
16 bits
30001-30100
Holding Register
Read-write
16 bits
40001-40100
Using modpoll tool, you can poll the first 5 holding registers via the following command,
modpoll --tcp modsim.topmaker.net --config https://raw.githubusercontent.com/gavinying/modpoll/master/examples/modsim.csvor run modpoll in docker,
docker run helloysd/modpoll modpoll --tcp modsim.topmaker.net --config https://raw.githubusercontent.com/gavinying/modpoll/master/examples/modsim.csvMeanwhile, if you prefer a local test or simply failed to connect to online modsim service, you can always launch your own device simulator via the following command,
docker run -p 5020:5020 helloysd/modsimIt will simulate a Modbus TCP device running at localhost:5020, and you shall be able to connect it via the following command,
modpoll --tcp localhost --tcp-port 5020 --config https://raw.githubusercontent.com/gavinying/modpoll/master/examples/modsim.csv