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I have written a server to publish on avahi via dbus. The same code working perfectly with Python 2.7, but throws error with Python 3.7

ERROR:dbus.connection:Unable to set arguments (dbus.Int32(-1), dbus.Int32(-1), dbus.UInt32(0), 'SETup', '_http._tcp', dbus.String('local'), 'surabhi-Latitude.local', dbus.UInt16(11732), dbus.Array(['f=abc', 't=test'], signature=dbus.Signature('ay'))) according to signature 'iiussssqaay': <class 'TypeError'>: an integer is required (got type str)
Traceback (most recent call last):
  File "myserver.py", line 17, in <module>
    avahiservice = AvahiService("SETup", "_http._tcp", current_port)
  File "/home/surabhi/Documents/set_buildv2/set_buildv2/avahiTest/service.py", line 42, in __init__
    dbus.Array(self.txt, signature='ay')) # TXT field, this is empty at the moment
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 70, in __call__
    return self._proxy_method(*args, **keywords)
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 641, in call_blocking
    message.append(signature=signature, *args)
TypeError: an integer is required (got type str)

This is my code:

class AvahiService:

    def __init__(self, service_name, service_type, port, keep_alive=False):
        """Announce a service over Avahi through dbus

        service_name: string with service's name
        service_type: string with service's type, eg. '_http._tcp'
        port: integer with port number
        keep_alive: whether to keep running this server until interruption.
                    Default is False. Use False if you run this script within your server,
                    use True if you are running this script as standalone, because the service
                    disappears as soon as the script stops otherwise.

        """
        self.bus = dbus.SystemBus()
        self.avahiserver = AvahiServer()
        self.path = self.avahiserver.EntryGroupNew()
        raw_server = self.bus.get_object('org.freedesktop.Avahi', self.path)
        self.server = dbus.Interface(raw_server, 'org.freedesktop.Avahi.EntryGroup')

        hostname, domainname = self.avahiserver.GetHostName(), self.avahiserver.GetDomainName()
                
        '''txt: TXT fields as array of string in a format of ["key1=value1", "key2=value2"], by default it's empty (ie. [])'''
        self.txt = ["f=abc", "t=test"]
        
        self.server.AddService(dbus.Int32(-1), # avahi.IF_UNSPEC
                               dbus.Int32(-1), # avahi.PROTO_UNSPEC
                               dbus.UInt32(0), # flags
                               service_name, # sname
                               service_type, # stype
                               domainname, # sdomain
                               "{}.{}".format(hostname, domainname), # shost
                               dbus.UInt16(port), # port
                               dbus.Array(self.txt, signature='ay')) # TXT field, this is empty at the moment
                               
        self.server.Commit()
        if keep_alive:
            while True:
                sleep(60)

when I pass txt as empty field, it works fine.

James Z
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SGP
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1 Answers1

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To resolve the issue, I added following functions to my code:

def string_to_byte_array(s):
    r = []
    for c in s:
        r.append(dbus.Byte(ord(c)))
    return r
def string_array_to_txt_array(t):
    l = []
    for s in t:
        l.append(string_to_byte_array(s))
    return l

and called string_array_to_txt_array() instead of dbus.Array()

SGP
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