bluez scanner for broadcast listening, only once per second

blescan.py

# BLE scanner based on https://github.com/adamf/BLE/blob/master/ble-scanner.py
# JCS 06/07/14

# https://github.com/pauloborges/bluez/blob/master/tools/hcitool.c for lescan
# https://kernel.googlesource.com/pub/scm/bluetooth/bluez/+/5.6/lib/hci.h for opcodes
# https://github.com/pauloborges/bluez/blob/master/lib/hci.c#L2782 for
# functions used by lescan

import binascii
import sys
import struct
import bluetooth._bluetooth as bluez

LE_META_EVENT = 0x3e
LE_PUBLIC_ADDRESS = 0x00
LE_RANDOM_ADDRESS = 0x01
LE_SET_SCAN_PARAMETERS_CP_SIZE = 7
OGF_LE_CTL = 0x08
OCF_LE_SET_SCAN_PARAMETERS = 0x000B
OCF_LE_SET_SCAN_ENABLE = 0x000C
OCF_LE_CREATE_CONN = 0x000D

LE_ROLE_MASTER = 0x00
LE_ROLE_SLAVE = 0x01

# these are actually subevents of LE_META_EVENT
EVT_LE_CONN_COMPLETE = 0x01
EVT_LE_ADVERTISING_REPORT = 0x02
EVT_LE_CONN_UPDATE_COMPLETE = 0x03
EVT_LE_READ_REMOTE_USED_FEATURES_COMPLETE = 0x04

# Advertisment event types
ADV_IND = 0x00
ADV_DIRECT_IND = 0x01
ADV_SCAN_IND = 0x02
ADV_NONCONN_IND = 0x03
ADV_SCAN_RSP = 0x04


def returnnumberpacket(pkt):
    myInteger = 0
    multiple = 256
    for c in pkt:
        myInteger += struct.unpack("B", c)[0] * multiple
        multiple = 1
    return myInteger


def returnstringpacket(pkt):
    myString = ""
    for c in pkt:
        myString += "%02x" % struct.unpack("B", c)[0]
    return myString


def printpacket(pkt):
    for c in pkt:
        sys.stdout.write("%02x " % struct.unpack("B", c)[0])


def get_packed_bdaddr(bdaddr_string):
    packable_addr = []
    addr = bdaddr_string.split(':')
    addr.reverse()
    for b in addr:
        packable_addr.append(int(b, 16))
    return struct.pack("<BBBBBB", *packable_addr)


def packed_bdaddr_to_string(bdaddr_packed):
    return ':'.join('%02x' % i for i in struct.unpack("<BBBBBB", bdaddr_packed[::-1]))


def hci_enable_le_scan(sock):
    hci_toggle_le_scan(sock, 0x01)


def hci_disable_le_scan(sock):
    hci_toggle_le_scan(sock, 0x00)

 
def hci_toggle_le_scan(sock, enable):
    cmd_pkt = struct.pack("<BB", enable, 0x00)
    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_SCAN_ENABLE, cmd_pkt)


def start_scan(sock):
    SCAN_TYPE = 0x01
    INTERVAL = 0x1
    WINDOW = 0x1
    OWN_TYPE = 0x01
    FILTER = 0x00 # all advertisements, not just whitelisted devices
    # interval and window are uint_16, so we pad them with 0x0
    cmd_pkt = struct.pack("<BBBBBBB", SCAN_TYPE, 0x0, INTERVAL, 0x0, WINDOW, OWN_TYPE, FILTER)
    bluez.hci_send_cmd(sock, OGF_LE_CTL, OCF_LE_SET_SCAN_PARAMETERS, cmd_pkt)
     
    hci_enable_le_scan(sock)
    
    flt = bluez.hci_filter_new()
    bluez.hci_filter_all_events(flt)
    bluez.hci_filter_set_ptype(flt, bluez.HCI_EVENT_PKT)
    sock.setsockopt(bluez.SOL_HCI, bluez.HCI_FILTER, flt)

def parse_event(sock):
    
    while True:
        pkt = sock.recv(255)
        ptype, event, plen = struct.unpack("BBB", pkt[:3])
        if event == LE_META_EVENT:
            subevent, = struct.unpack("B", pkt[3])
            pkt = pkt[4:]
            if subevent == EVT_LE_ADVERTISING_REPORT:
                # print "advertising report"
                num_reports = struct.unpack("B", pkt[0])[0]
                for report in range(0, num_reports):
                    
                    address = packed_bdaddr_to_string(
                        pkt[3:9])
                    
                    if address != '04:a3:16:9a:f3:22':
                        continue
                                        
                    rssi = struct.unpack("b", pkt[-1])
                    
                    rest_bin = pkt[9:-2]
                    rest = binascii.b2a_hex(rest_bin).decode('utf-8')
                    
                    return [address, rssi, rest]

 def main():
    dev_id = 0
    try:
      sock = bluez.hci_open_dev(dev_id)
      print "ble thread started"

    except:
      print "error accessing bluetooth device..."
          sys.exit(1)

    blescan.start_scan(sock)

    while True:
        beacon = blescan.parse_event(sock)
        print beacon
        print "----------"