Python server for Wialon Retranslator 1.0

parser.py

# -*- coding: utf-8 -*-

import binascii
import struct


def parse(fmt, binary, offset=0):
    '''
    Unpack the string

    fmt      @see https://docs.python.org/2/library/struct.html#format-strings
    value    value to be formated
    offset   offset in bytes from begining
    '''
    parsed = struct.unpack_from(fmt, binary, offset)
    return parsed[0] if len(parsed) == 1 else parsed


def parsePacket(packet):
    '''
    Parse Wialon Retranslator v1.0 packet w/o first 4 bytes (packet size)
    '''

    # parsed message
    msg = {
        'id': 0,
        'time': 0,
        'flags': 0,
        'params': {},
        'blocks': []
    }

    # parse packet info
    controller_id_size = packet.find('\x00')
    (msg['id'], msg['time'], msg['flags']) = parse('> %ds x i i' % (controller_id_size), packet)

    # get data block
    data_blocks = packet[controller_id_size + 1 + 4 + 4:]

    while len(data_blocks):
        # name offset in data block
        offset = 2 + 4 + 1 + 1
        name_size = data_blocks.find('\x00', offset) - offset
        (block_type, block_length, visible, data_type, name) = parse('> h i b b %ds' % (name_size), data_blocks)

        # constuct block info
        block = {
            'type': block_type,
            'length': block_length,
            'visibility': visible,
            'data_type': data_type,
            'name': name
        }

        # get block data
        block['data_block'] = data_blocks[offset + name_size + 1:block_length * 1 + 6]

        v = ''
        if data_type == 1:
            # text
            # TODO
            pass
        if data_type == 2:
            # binary
            if name == 'posinfo':
                v = {'lat': 0, 'lon': 0, 'h': 0, 's': 0, 'c': 0, 'sc': 0}
                (v['lon'], v['lat'], v['h']) = parse('d d d', block['data_block'])
                (v['s'], v['c'], v['sc']) = parse('> h h b', block['data_block'], 24)
        elif data_type == 3:
            # integer
            v = parse('> i', block['data_block'])
        elif data_type == 4:
            # float
            v = parse('d', block['data_block'])
        elif data_type == 5:
            # long
            v = parse('> q', block['data_block'])

        # add param to message
        msg['params'][name] = v

        # data blocks parse information
        msg['blocks'].append(block)

        # delete parsed info
        data_blocks = data_blocks[block_length + 6:]

    return msg

if __name__ == '__main__':
    # test data
    data = [
        '333533393736303133343435343835004B0BFB70000000030BBB000000270102706F73696E666F00A027AFDF5D9848403AC7253383DD4B400000000000805A40003601460B0BBB0000001200047077725F657874002B8716D9CE973B400BBB00000011010361766C5F696E707574730000000001',
        '73686d6900552d3f49000000070bbb000000270102706f73696e666f001f090e42538d3b40af8c20a82dfc4a400000000000000000006c0109ff0bbb0000000f000461646331000000000000ca21400bbb00000011010361766c5f696e7075747300000000240bbb00000012010361766c5f6f7574707574730000000037'
    ]
    for i in range(len(data)):
        print '\nParse packet: %s\n' % data[i]
        print parsePacket(binascii.unhexlify(data[i]))

server.py

# -*- coding: utf-8 -*-

import binascii
import socket

from parser import parse, parsePacket

CONNECTION = (socket.gethostname(), 12374)

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

# prevent 'ERROR: Address already in use'
server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)


server.bind((socket.gethostname(), 12374))
server.listen(1)

print "Listen {0} on {1}".format(*CONNECTION)
# Accept connections
sck, addr = server.accept()
print "Connected {0}:{1}".format(*addr)

# packet queue
queue = ''

while 1:
    data = sck.recv(1024)
    if not data:
        break
    # append to queue
    queue = queue + data

    # get first packet size
    packet_size = parse('<i', queue)
    if packet_size + 4 <= len(queue):
        # get packet
        packet = queue[4:packet_size + 4]

        # print binascii.hexlify(packet)
        print parsePacket(packet)

        # remove packet from queue
        queue = queue[packet_size + 4:]

        # packet was received successfully
        sck.send(str(0x11))

Hi Aleksey, thank you for this parsePacket function, I have found it very useful!

I noticed on some test data from a wialon local retranslator, that the latitude appeared to be in the 'lon' value and the longitude in the 'lat' value.

If I parse the following sample data using this function:
'333533393736303133343435343835004B0BFB70000000030BBB000000270102706F73696E666F00A027AFDF5D9848403AC7253383DD4B400000000000805A40003601460B0BBB0000001200047077725F657874002B8716D9CE973B400BBB00000011010361766C5F696E707574730000000001'
it yields: 'posinfo': {'c': 326, 'h': 106.0, 'lon': 55.7305664, 'sc': 11, 's': 54, 'lat': 49.1903648} which locates to here: https://www.google.com/maps/search/+49.1903648+55.7305664
Is this correct? Or is it supposed to be here:
https://www.google.com/maps/search/+55.7305664+49.1903648

I modified lines 66-67 to the following, which appears to resolve for me:
v = {'lon': 0, 'lat': 0, 'h': 0, 's': 0, 'c': 0, 'sc': 0}
(v['lon'], v['lat'], v['h']) = parse('d d d', block['data_block'])

Could this be a mistake or could there be some other reason for this being jumbled up in my environment?

Hey @bshaw-au
WOW! What a bug) So many years it was in this code!

In spec 'posinfo' binary block has structure (lon-lat)

(bytes)    Type                 Field description
8          Fractional value     Lon - longitude
8          Fractional value     Lat - latitude

So you're right, line 67 must be like this

-(v['lat'], v['lon'], v['h']) = parse('d d d', block['data_block'])
+(v['lon'], v['lat'], v['h']) = parse('d d d', block['data_block'])

I already updated code
Thanks for reporting!