How to get 2 responses from the server using Promise?

Question

JavaScript

On request from the server, 2 response lines are returned in turn, In the code I get only one!

const net = require("net");

const HOST = '192.168.0.75';
const PORT = '30001';

class Api {

    constructor(host, port) {
        this.HOST = host || HOST;
        this.PORT = port || PORT;
        this.socket = new net.Socket();

        this.init();
    }

    init() {
        const client = this;

        client.socket.connect(client.PORT, client.HOST, () => {
            console.log(`Client connected to: ${client.HOST}:${client.PORT}`);
        });

        client.socket.on('close', () => {
            console.log('FiscalAPI: connection closed');
        });
    };

    sendCommand(cmd) {
        const client = this;

        return new Promise((resolve, reject) => {
            if(cmd) {
                client.socket.write(cmd + '\u0000\r\n');
            }

            client.socket.on('data', (data) => {
                    resolve(data.toString());
            });

            client.socket.on('error', (error) => {
                reject(error);
            });
        });
    };

    checkPumpState(dispenser_index){
        this.sendCommand('0;open')
            .then((data) => {
                console.log(data);
                return this.sendCommand(`0;dispenser_get;${dispenser_index};1`);
            })
            .then((data) => {
                console.log(data);
                return this.sendCommand(`0;store_get;0;16\u0000\r\n`);
            })
            .then((data) => {
                console.log(data);
            })
            .catch((error) => console.log(error));
    }
}

2 responses are returned for each request. First: echo of the request, second: the result needed to continue.
This code only manages to get the first response - echo. How to get the second one too?
PS
Another important point: REQUESTS-RESPONSES must go in strict sequence, the answer to the previous request can be used as data for the next

Answer 1

I don’t really understand what’s going on here, but I’ll assume that your event client.socket.on('data')is called twice - for each response from the server. And you return the promise as soon as you get the first answer.
UPD accept all data but only return on 'end' event

sendCommand(cmd) {
    if(cmd) {
      this.socket.write(cmd + '\u0000\r\n');
    }
    
      return new Promise((resolve, reject) => {
        const chunks = [];
        
        const handleData = chunk => {
          chunks.push(chunk);
        };

        const handleError = err => {
          reject(err);
        };

        const handleEnd => {
          const data = Buffer.concat(chunks).toString().match(/.*?\r\n/g);
          resolve(data);
        }

        this.socket.on('data', handleData);
        this.socket.on('error', handleError);
        this.socket.on('end', handleEnd);
      });
  }

Answer 2

sendCommand creates a subscriber every time it is called, something tells me that your server is running out of memory