TCP / RTU Client Manager

[alexbuczynsky]

Summary

Every time I use jsmodbus in one of my projects, I wind up creating a utility class to manage all the clients. I also like to make sure that only one socket is being used for a single host:port combination at a time like the image below show:

This pull request adds two main new classes:

1. ModbusTCPClientManager
2. ModbusRTUClientManager

Description

The class manages the active socket connections and only allows one socket connection open to any modbus master at a time. Each client then uses the same socket reference if the client matches the host and port number of that already created socket.

For example, for the ModbusTCPClientManager it keeps a record of the host and port that each client being added to the system has and assigns the correct currently active socket connection to the clients as they are added. The image below shows a diagram of how this works.

Below is an example use case for why this manager can be very useful:

const modbus = require('jsmodbus')

const manager = new modbus.ModbusTCPClientManager()

const socket = manager.findOrCreateSocket({
  host: 'localhost',
  port: 5052,
})

for(let i = 0; i < 50; i++) {
  manager.findOrCreateClient({
    host: 'localhost',
    port: 5052,
    slaveId: i
  })
}


console.log(manager.clientCount) // should be 50
console.log(manager.socketCount) // should be 1


socket.on('connect', () => {
  console.log('SOCKET CONNECTED')

  setInterval(() => {
    for(const [clientId, client] of manager.clients){
      client
        .readCoils(0, 5)
        .then(({response}) => console.log(response.body.valuesAsArray))
        .catch(console.error)
    }
  }, 1000)
})

---

Notes:

BLOCKED WHILE WAITING FOR #254
The version should be bumped to 4.1 since this is a new feature

[stefanpoeter]

Hey @alexbuczynsky

this is indeed a useful feature, thanks for your work. I will check your code in the next days and write some feedback if necessary.

[stefanpoeter]

Hey @alexbuczynsky,

common things I noticed that I could not annotate in your code. First the standard linter is missing in the package.json for the js files. There are a lot of complaints about assert.equals is deprecated, wrong indentation etc. Please change the following in the package.json

"lint": "tslint -c tslint.json 'src/**/*.ts' **&& standard**",

Some Tests are marked with ToDo, what is it about that?

[stefanpoeter]

Test Case for when a client is not found?

[stefanpoeter]

host and port are undefined

[stefanpoeter]

Is it a common use case to add or remove clients during runtime? Have you checked the memory behaviour in that case?

[alexbuczynsky]

@stefanpoeter sorry I have been extremely busy with work. Will get back to this as soon as I can. A couple of comments for now...

Linting
We will have to move the linting to a new PR. Typescript tslint has been deprecated in favor of regular eslint. There is an easy way to setup your project via the cli to do the linting of your typescript code with support out of the box for standardjs style guide.

Missing test cases
completely forgot to add those. will go back and do that

Memory Behavior

Is it a common use case to add or remove clients during runtime? Have you checked the memory behaviour in that case?

I used the same client manager class for a work based project. The server has been running for the past 3 months without any noticeable memory issues. If we want data to back up that statement, I would have to run some stress test to check this.

[stefanpoeter]

Hi @alexbuczynsky no need to be sorry. This is a open source project so you do what you do when you do it :-)

Some data to check the memory behaviour would be great :-)

[arobal]

Hi,

I just tried to build the changes on Ubuntu, but it fails building some dependencies of the serialport package (see logs).

2021-12-23T10_27_10_780Z-debug.log