Two Lopy communicate via BLE, LOSE connection, CANNOT read service.

[yunying]

Hello, I am trying communicate two lopy use BLE, one is server, another is client.
The server success advertising and client could notice and connect. But we I am trying to for loop the service, it goes wrong and of course, I cannot read the characteristic.

Here is the server code.

from network import Bluetooth
bluetooth = Bluetooth()
bluetooth.init()
#config data before send
bluetooth.set_advertisement(name='LoPy', manufacturer_data = 'lopy_server_1',  service_data = b'19950922' ,service_uuid=b'1000000010000000')
#bluetooth.set_advertisement(name='LoPy', service_data = b'19950922' , service_uuid=b'1234567890123456')
def conn_cb (bt_o):
    events = bt_o.events() # this method returns the flags and clears the internal registry
    if  events & Bluetooth.CLIENT_CONNECTED:
        print("Client connected")
        #not sure
        bt_o.advertise(False)
    elif events & Bluetooth.CLIENT_DISCONNECTED:
        print("Client disconnected")
        #not sure
        bt_o.advertise(True)
bluetooth.callback(trigger=Bluetooth.CLIENT_CONNECTED | Bluetooth.CLIENT_DISCONNECTED, handler=conn_cb)
#start advertise 
bluetooth.advertise(True)
#Create a new service on the internal GATT server. Returns a object of type BluetoothServerService.
#bluetooth.service(uuid, *, isprimary=True, nbr_chars=1, start=True)
# start = True service start immediately
srv1 = bluetooth.service(uuid=b'1000000010000000', isprimary=True, nbr_chars=1, start = True)
chr1 = srv1.characteristic(uuid = b'ab34567890123456', properties = Bluetooth.PROP_READ, value=99999,  permissions = (1 << 0) | (1 << 4))
#property = Bluetooth.PROP_READ | Bluetooth.PROP_WRITE
char1_read_counter = 0
def char1_cb_handler(chr):
    global char1_read_counter
    char1_read_counter += 1
    events = chr.events()
    if  events & Bluetooth.CHAR_WRITE_EVENT:
        print("Write request with value = {}".format(chr.value()))
    else:
        print('Read request on char 1')       
char1_cb = chr1.callback(trigger=Bluetooth.CHAR_WRITE_EVENT | Bluetooth.CHAR_READ_EVENT, handler=char1_cb_handler)
#char1_cb = chr1.callback(trigger=Bluetooth.CHAR_NOTIFY_EVENT, handler=char1_cb_handler)

Here is the client code

from network import Bluetooth
import time
bt = Bluetooth()
bt.start_scan(-1)

while True:
    adv = bt.get_adv()
    # resolve_adv_data(data , datatype)
    #bt.resolve_adv_data(adv.data, Bluetooth.ADV_NAME_CMPL) == 'Heart Rate'
    #  if adv and bt.resolve_adv_data(adv.data, Bluetooth.ADV_NAME_CMPL) == 'LoPy':
    if adv and bt.resolve_adv_data(adv.data, Bluetooth.ADV_NAME_CMPL) == 'LoPy':
        # stop scan before connect
        bt.stop_scan()
        print('333')
        try:
            connection = bt.connect(adv.mac)  
            if(connection.isconnected()):
                print("Connection opened!")
     
            # a list of services
            services = connection.services()    
            print('555')
            time.sleep(0.050)
            for service in services:
                print('444')
                time.sleep(0.050)
                print('Reading chars from service = {}'.format(service.uuid()))
                    
                chars = service.characteristics()
                for char in chars:
                    print('char {} value = {}'.format(char.uuid(), char.read()))
            connection.disconnect()
            break
 
        except:
            print("Error while connecting or reading from the BLE device")
            break
    else:
        time.sleep(0.050)

I already add stop scan, but connection.isconnected() never work.
I also try to move connection.isconnected() but after connect, the service never show.