CODEWITHSUNDEEP
javascriptnode.js
Lieke
Lieke

Reputation: 51

promise.then doesn't get called

I'm trying to search for an active comport open it and then call the then. Everything works exept the then and i don't understand why.

Does anyone have experience with this problem i also tried a simple promise. in that example the then works like supposed to.

result of code 

let getActiveComPort = new Promise((resolve, reject) => {
    let max = 5;
    for (let index = 1; index <= max; index++) {
        // create a port with the index to test
        const port = new SerialPort(`COM${index}`, {
            baudRate: 115200,
            autoOpen: false,
        });

        // Try opening the port if error reject
        port.open((error) => {
            if (error) {
                console.log(error, "couldnt open port", index);
                return reject(error);
            }
        });

        // if the port is opened resolve promise
        port.on("open", () => {
            console.log("resolved port", index);
            return resolve(port);
        });
    }
});
getActiveComPort
    .then((port) => {
        // set ledstrip to white
        console.log(
            "comport _______________"
        );
        console.log("comport", port);
        port.write(`X002B[290005]\r\n`);
    })
    .catch((error) => {
        console.log(error);
    });

`

Upvotes: 1

Views: 635

Answers (1)

AKX
AKX

Reputation: 168966

You'll want to split things so you have a single function that tries a single COM port, then another that tries them in sequence, something like

function tryComPort(index) {
  return new Promise((resolve, reject) => {
    const port = new SerialPort(`COM${index}`, {
      baudRate: 115200,
      autoOpen: false,
    });

    // Try opening the port if error reject
    port.open((error) => {
      if (error) {
        return reject({ index, port, error });
      }
    });

    port.on("open", () => {
      return resolve({ index, port });
    });
  });
}

async function tryComPorts(max = 5) {
  for (let index = 1; index <= max; index++) {
    try {
      return await tryComPort(index);
    } catch (err) {
      console.error(err);
    }
  }
  throw new Error("Failed all attempts at COM port opening");
}

tryComPorts()
  .then(({ index, port }) => {
    console.log(`comport ${index}`);
    console.log("comport", port);
    port.write(`X002B[290005]\r\n`);
  })
  .catch((error) => {
    console.error(error);
  });

Upvotes: 1

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