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Print only work the first time and I need to restart the bluetooth to print again.

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
express, node.js
Domain
api, backend

Research direction

Start with the printerService.js example and trace Bluetooth.findPrinters, device.open, and the qrimage callback across repeated print requests. Reproduce the listener warning and one-print-only behavior, then verify that repeated prints complete without restarting Bluetooth or accumulating listeners.

Written by the indexing model from the issue text.

Description

I want to create a REST service with Node.js using Express that prints tickets to ESC/POS bluetooth printer.

The actual result my service print only the first time and I need to restart the bluetooth to print again.

I tried update my service to only look for the printer and return it but it only works a couple of times. I received this error in the console:

(node:16608) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added to [Device]. Use emitter.setMaxListeners() to increase limit (Use node --trace-warnings ... to show where the warning was created)

The expected result print data multiple times

Here is my printerService.js :

const { Printer } = require("escpos");
const Bluetooth = require("escpos-bluetooth");

const foundPrinter = async (name, address, channel, printData) => {
  const PRINTER_NAME = name;
  const PRINTER_ADDRESS = address;
  const PRINTER_CHANNEL = channel;
  const preferredPrinterAddress = "(" + PRINTER_ADDRESS + ")" + PRINTER_NAME;
  const availablePrinters = await Bluetooth.findPrinters();
  console.log("availablePrinters", availablePrinters);
  const btPrinter =
    availablePrinters && availablePrinters.length > 0
      ? availablePrinters.filter(
          (p) =>
            p &&
            p.name === PRINTER_NAME &&
            p.address === preferredPrinterAddress
        )[0]
      : false;

  console.log("btPrinter", btPrinter);
  return new Promise((resolve, reject) => {
    if (btPrinter) {
      if (!printData) {
        resolve({ printer: btPrinter });
      } else {
        const device = new Bluetooth(PRINTER_ADDRESS, PRINTER_CHANNEL);
        const printer = new Printer(device);
        device.open(function (deviceError) {
          if (!deviceError) {
            printer
              .font("a")
              .align("ct")
              .style("bu")
              .size(1, 1)
              .text("Text1")
              .text("Text2")
              .barcode("1234567", "EAN8")
              .qrimage("qrImage", function (qrImageError) {
                if (!qrImageError) {
                  this.cut();
                  this.close();
                } else {
                  reject({
                    name: qrImageError.name,
                    message: qrImageError.message,
                  });
                }
              });
            resolve({ printer: btPrinter });
          } else {
            reject({ name: deviceError.name, message: deviceError.message });
          }
        });
      }
    } else {
      reject({
        errorType: "ERROR_PRINTER_NOT_FOUND",
        errorName: "PRINTER_NOT_FOUND",
        message: "printer not found",
        fullMessage:
          "printer not found, availablePrinters: " +
          availablePrinters.toString(),
      });
    }
  });
};
Dominant language
TypeScript
Stars
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Forks
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Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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