README.md

BLE Server

This is the code to create a basic BLE Server to share data to a BLE client

Terminal Output (BLE Server)

Phone Screen recording (BLE client)

screen-20251222-233715.mp4

Code

use esp32_nimble::{uuid128, BLEAdvertisementData, BLEDevice, NimbleProperties};
use std::format;

fn main() -> anyhow::Result<()> {
  esp_idf_svc::sys::link_patches();
  esp_idf_svc::log::EspLogger::initialize_default();

  let ble_device = BLEDevice::take();
  let ble_advertising = ble_device.get_advertising();
  
  let server = ble_device.get_server();
  server.on_connect(|server, desc| {
    ::log::info!("Client connected: {:?}", desc);

    server
      .update_conn_params(desc.conn_handle(), 24, 48, 0, 60)
      .unwrap();

    if server.connected_count() < (esp_idf_svc::sys::CONFIG_BT_NIMBLE_MAX_CONNECTIONS as _) {
      ::log::info!("Multi-connect support: start advertising");
      ble_advertising.lock().start().unwrap();
    }
  });

  server.on_disconnect(|_desc, reason| {
    ::log::info!("Client disconnected ({:?})", reason);
  });

  let service = server.create_service(uuid128!("fafafafa-fafa-fafa-fafa-fafafafafafa"));

  // A static characteristic.
  let static_characteristic = service.lock().create_characteristic(
    uuid128!("d4e0e0d0-1a2b-11e9-ab14-d663bd873d93"),
    NimbleProperties::READ,
  );
  static_characteristic
    .lock()
    .set_value("Hello, world!".as_bytes());

  // A characteristic that notifies every second.
  let notifying_characteristic = service.lock().create_characteristic(
    uuid128!("a3c87500-8ed3-4bdf-8a39-a01bebede295"),
    NimbleProperties::READ | NimbleProperties::NOTIFY,
  );
  notifying_characteristic.lock().set_value(b"Initial value.");

  // A writable characteristic.
  let writable_characteristic = service.lock().create_characteristic(
    uuid128!("3c9a3f00-8ed3-4bdf-8a39-a01bebede295"),
    NimbleProperties::READ | NimbleProperties::WRITE,
  );
  writable_characteristic
    .lock()
    .on_read(move |_, _| {
      ::log::info!("Read from writable characteristic.");
    })
    .on_write(|args| {
      ::log::info!(
        "Wrote to writable characteristic: {:?} -> {:?}",
        args.current_data(),
        args.recv_data()
      );
    });

  ble_advertising.lock().set_data(
    BLEAdvertisementData::new()
      .name("ESP32-GATT-Server")
      .add_service_uuid(uuid128!("fafafafa-fafa-fafa-fafa-fafafafafafa")),
  )?;
  ble_advertising.lock().start()?;

  server.ble_gatts_show_local();

  let mut counter = 0;
  loop {
    esp_idf_svc::hal::delay::FreeRtos::delay_ms(1000);
    notifying_characteristic
      .lock()
      .set_value(format!("Counter: {counter}").as_bytes())
      .notify();

    counter += 1;
  }
}