Sending messages or datas with bluetooth via python

I had the same error. After binding the address the error went away.

rfcomm bind 0 <address> 1

The 0 refers to your bluetooth device. The 1 refers to the port number. If you're running linux you can run hciconfig to the the device number.

As @TJD said, you need to ensure you bind with the correct port for the service you want.

>>> from bluetooth import *
>>> from pprint import pprint
>>>
>>> devices = discover_devices()
>>> devices
['xx:yy:tt:zz:44:BD', '00:yy:72:zz:bb:aa']

Then as the second step try to find the service on the device you want to connect to.

>>> service = find_service(address='00:yy:72:zz:bb:aa')
>>> pprint(service)
[{'description': None,
  'host': '00:yy:72:zz:bb:aa',
  'name': 'Headset Audio Gateway',
  'port': 12,
  'profiles': [('1108', 258)],
  ...},
 {'description': None,
  'host': '00:yy:72:zz:bb:aa',
  'name': 'Dial-Up Networking',
  'port': 1,
  'profiles': [('1103', 256)],
  'protocol': 'RFCOMM',
  ...}]

Based on this information you can connect to a service running on a device. According to the service/profile specification you send service specific commands and get back information from the device. E.g. in the list above you see the 'Headset Audio Gateway' and the profile list with the number '1108', which is the short uuid for the service. You can now lookup the commands for this profile and it should work.