Is it possible to transfer files using web-bluetooth technology?

Question

Is it possible to transfer files using web-bluetooth technology?

As I work on developing an embedded system that counts the number of cars, saves their speed and time data in a logs file using rsyslog. Simultaneously, I am creating a web-API (in Typescript/Angular with Electron for Desktop usage and later Web as well) that allows users to upload these logs and store them locally on their laptops.

I have successfully set up a GATT server and can acquire simple data like battery level and status over Web-Bluetooth. However, I am unsure if it is possible to send/receive a file using Web-Bluetooth or perhaps send it piece by piece.

My attempt at sending the file in pieces involved dividing the file size by 512 bytes per frame and transmitting X frame(s) to the Web-App. Unfortunately, I encountered issues after a few days of trying this method. This led me to discover information on Bluetooth's website about the 'Object Transfer Service' available with GATT. However, upon further investigation, it appears that this service primarily supports bulk data transfer via a separate L2CAP connection orientel channel, which raised questions about the possibility of sending files.

Considering the challenges faced with Web-Bluetooth, I am contemplating whether it would be more feasible to modify my plan and utilize a different protocol for transferring files between the laptop and the embedded system, specifically for tasks such as sending configuration files and parameters.

javascript typescript bluetooth-lowenergy bluetooth-gatt web-bluetooth

Answer 1

Answer №1

After experimenting with different approaches, I've come up with a solution that seems to work quite effectively. Essentially, I'm dividing my Uint8Array[] into packets of 512 bytes for transmission, writing, and reading. Below is the TypeScript code I've used:

async getFile() {
    let file: string = '';
    let value: string = 'begin';
    let returnedValue = null;

    while (value != '') {
      try {
        returnedValue = await this.characteristicScheduling.readValue();
        value = String.fromCharCode.apply(null, new Uint8Array(returnedValue.buffer));
        console.log(value);
        file= file.concat(value);

      } catch(e) {
        console.log(e);
      }
    }

    console.log('file: ' + file);
}

And here's the write function:

wait(ms: number) {
    var start = new Date().getTime();
    var end = start;
    while(end < start + ms) {
      end = new Date().getTime();
    }
}

pushFile() {
    let file= this.getFileContent();
    let value: string;
    let valueBytes = null;
    console.log(file);

    while (file.length > 0) {
      // Copy the first 512 bytes
      value = file.substr(0, 512);
      // Remove the first 512 bytes
      scheduling = file.substr(512)
      console.log(file);
      valueBytes = new TextEncoder().encode(value);

      console.log(valueBytes);
      const promise = this.characteristic.writeValue(valueBytes);
      promise.then(val => {
        console.log(val);
      });
      // The wait is isn't mandatory .. but just in case my embedded system is very busy
      this.wait(100);
    }

    // Send empty frame to notify the Embedded system that it's the end of transmission
    valueBytes = new TextEncoder().encode('');
    const promise = this.characteristic.writeValue(valueBytes);
      promise.then(val => {
        console.log(val);
      });
}

For more information on Web Bluetooth characteristics, refer to this link.

As an embedded engineer, my web-coding skills may not be perfect. Feel free to provide recommendations on how to optimize this code. I hope this code snippet proves helpful to others.

Answer 2

After experimenting with different approaches, I've come up with a solution that seems to work quite effectively. Essentially, I'm dividing my Uint8Array[] into packets of 512 bytes for transmission, writing, and reading. Below is the TypeScript code I've used:

async getFile() {
    let file: string = '';
    let value: string = 'begin';
    let returnedValue = null;

    while (value != '') {
      try {
        returnedValue = await this.characteristicScheduling.readValue();
        value = String.fromCharCode.apply(null, new Uint8Array(returnedValue.buffer));
        console.log(value);
        file= file.concat(value);

      } catch(e) {
        console.log(e);
      }
    }

    console.log('file: ' + file);
}

And here's the write function:

wait(ms: number) {
    var start = new Date().getTime();
    var end = start;
    while(end < start + ms) {
      end = new Date().getTime();
    }
}

pushFile() {
    let file= this.getFileContent();
    let value: string;
    let valueBytes = null;
    console.log(file);

    while (file.length > 0) {
      // Copy the first 512 bytes
      value = file.substr(0, 512);
      // Remove the first 512 bytes
      scheduling = file.substr(512)
      console.log(file);
      valueBytes = new TextEncoder().encode(value);

      console.log(valueBytes);
      const promise = this.characteristic.writeValue(valueBytes);
      promise.then(val => {
        console.log(val);
      });
      // The wait is isn't mandatory .. but just in case my embedded system is very busy
      this.wait(100);
    }

    // Send empty frame to notify the Embedded system that it's the end of transmission
    valueBytes = new TextEncoder().encode('');
    const promise = this.characteristic.writeValue(valueBytes);
      promise.then(val => {
        console.log(val);
      });
}

For more information on Web Bluetooth characteristics, refer to this link.

As an embedded engineer, my web-coding skills may not be perfect. Feel free to provide recommendations on how to optimize this code. I hope this code snippet proves helpful to others.

Is it possible to transfer files using web-bluetooth technology?

Answer №1

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