node ethernet IP read and write strings

const { Controller, Tag, EthernetIP } = require("ethernet-ip");
const { SINT, DINT } = EthernetIP.CIP.DataTypes.Types;
 
const PLC = new Controller();


const readString = (name)=>{
    return new Promise(async (res, rej)=>{
        try{
            str = ''
            for(let i=0;i<82;i++){
                let t = new Tag(name + `.DATA[${i}]`, null, SINT);
                await PLC.readTag(t);
                if(!t.value){
                    break;
                }
                str += String.fromCharCode(t.value)
            }
            res(str);
        }
        catch(err){
            rej(err)
        }
    })
}

const writeString = (name, str)=>{
    return new Promise(async (res, rej)=>{
        try{
            let len = Math.min(str.length, 81);
            let buff = Buffer.from(str);
            for(let i=0;i<82;i++){
                let t = new Tag(name + `.DATA[${i}]`, null, SINT);
                if(buff.length >= i - 1){
                    t.value = buff[i]
                } else {
                    t.value = 0; //NULL Term
                }
                await PLC.writeTag(t);
            }
            let l = new Tag(name + `.LEN`, null, DINT);
            l.value = len;
            await PLC.writeTag(l);
            res(len);
        }
        catch(err){
            rej(err)
        }
    })
}


const DI_len = 32;
const DO_len = 16;







PLC.connect("10.10.90.175", 0).then(async () => {
    try{
        for(let chan=0; chan<DI_len; chan++){
            await writeString(`Area01_DI_03_ChanDesc[${chan}]`, `New Chan ${chan}`)
            let str = await readString(`Area01_DI_03_ChanDesc[${chan}]`)
            console.log(str)
        }
    }
    catch(err){
        console.log(err)
    }
});