正在学Python小试牛刀访问modbus从站点

var net = require('net');



var HOST = '127.0.0.1';

var PORT = 502;



//          transactionID   Protocol    DatSize     Addr  CMD-ReadReg   CMD-Reg-Addr  CMD-Reg-Count 

const cmd = Buffer.from([ 0x55, 0xAA,   0, 0,       0, 6,       0x09,   0x03,       0x13, 0x94,      0, 2 ]);



var tcp = new net.Socket();

tcp.connect(PORT, HOST, function() {

    console.log('CONNECTED TO: ' + HOST + ':' + PORT);

});





tcp.on('data', function(ack){

        var sLine = "Recv: ";

        for(var i=0;i<ack.length;i++)

                sLine += ack[i].toString(16) + ' ';

        

        console.log( sLine );



//        console.log( '\n' )

        console.log( "CMD->Transaction ID:" + (cmd[0]*256+cmd[1]) )

        console.log( "CMD->Protocol    ID:" + (cmd[2]*256+cmd[3]) )

        console.log( "CMD->Data      Size:" + (cmd[4]*256+cmd[5]) )

        console.log( "CMD->Device    Addr:" + (cmd[6]) )

        console.log( "CMD->Operation  CMD:" + (cmd[7]) )

        console.log( "CMD->Register  Addr:" + (cmd[8]*256+cmd[9]) )

        console.log( "CMD->Register Count:" + (cmd[10]*256+cmd[11]) )

//        console.log( "\n" )

        console.log( "ACK->Transaction ID:" + (ack[0]*256+ack[1]) )

        console.log( "ACK->Protocol    ID:" + (ack[2]*256+ack[3]) )

        console.log( "ACK->Data      Size:" + (ack[4]*256+ack[5]) )

        console.log( "ACK->Device    Addr:" + (ack[6]) )

        console.log( "ACK->Operation  CMD:" + (ack[7]) )

        console.log( "ACK->Raw Data  Size:" + (ack[8]) )

        console.log( "ACK->Register[" + (cmd[8]*256+cmd[9]+0) + "]:" + (ack[9]*256+ack[10]) )

        console.log( "ACK->Register[" + (cmd[8]*256+cmd[9]+1) + "]:" + (ack[11]*256+ack[12]) )



});



tcp.on('close', function() {

    console.log('Connection closed');

});



var nCnt = 0;



setInterval(function(){

        console.log( ">>>>---------------------------------------->>>" )



        var Tim = new Date();

        console.log( Tim.getFullYear() + '.' + Tim.getMonth() + '.' + Tim.getDate() + '-' + Tim.getHours() + ':' + Tim.getMinutes() + ':' + Tim.getSeconds() )





        tcp.write(cmd);



        var sLine = "Send: ";

        for(var i=0;i<cmd.length;i++)

                sLine += cmd[i].toString(16) + ' ';

        console.log( sLine );



        if(nCnt>10)

                client.destroy();

        nCnt++;



},3000);