index.js

const net = require('net');
const parser_content = require('./parser_content');

net.createServer((connection) => {
    connection.on('data', (data) => {
        console.log(connection.remoteAddress)
	    console.log(data);
        if (data.length == 17){
            let response = Buffer.from('01', 'hex');
            let IMEI = data;
            IMEI = IMEI.toString().slice(2);
            console.log(data.toString());
            connection.write(response);
        }
        else{
            let payload = data.slice(0, 8);
            let contentlength = payload.slice(4,8);
            console.log("payload " + contentlength.readUInt32BE() + "----------------");
            console.log(payload);

            let content = data.slice(8, contentlength.readUInt32BE());
            console.log("content----------------------");
            console.log(content);
            let information = parser_content(content);
            console.log("--------------------------------")
            console.log(information);

            let latitude = Buffer.allocUnsafe(4);
            let longitude = Buffer.allocUnsafe(4);
        
            latitude.writeUInt32BE(information.pop().latitude);
            longitude.writeUInt32BE(information.pop().longitude);
            latitude = latitude.readInt32BE()/Math.pow(10,7);
            longitude = longitude.readInt32BE()/Math.pow(10,7);
            console.log(`latitude: ${latitude} | longitude: ${longitude}`);

            connection.write(Buffer.from("00000002", 'hex'));
        }

    });
}).listen(12000, '0.0.0.0');