Python smpplib truncating smpp credentials - python-3.x

Question

I am using Python SMPP lib to send a SMS. When I try to connect to SmppServer with a longer credentials the username and password are getting truncated and authorisation is failing.
Auth failing case:
- Username/password longer than 16 char length
Passing case:
- Username/password not longer than 16 char
So because of the above observation I am sure there is no issue with the SMMPP gateway. The gateway I am trying to communicate itself accepts of username/password of any length.
The following is my code which wraps the smpplib in to a custom class:
import smpplib
import smpplib.gsm
from smpplib.client import Client
class SmppClientConfig(object, ):
def __init__(self, host, port, username, password, source, target, on_delivered_cb, on_sent_cb):
self.HOST = host
self.PORT = port
self.USERNAME = username
self.PASSWORD = password
self.SOURCE = source
self.TARGET = target
self.ON_RECEIVED_CALLBACK = on_sent_cb
self.ON_DELIVERED_CALLBACK = on_delivered_cb
class SmppSenderClient(object):
def __init__(self, config: SmppClientConfig):
print('Creating SMPP client config with host: ' + config.HOST + ' port: ' + str(config.PORT))
self._config = config
self._client = Client(config.HOST, config.PORT)
self._on_delivered_callback = config.ON_DELIVERED_CALLBACK
self._on_received_callback = config.ON_RECEIVED_CALLBACK
self._init_client()
def _init_client(self):
print('Initializing SmppSender client with username: ' + self._config.USERNAME)
self._register_events()
self._client.connect()
self._client.bind_transmitter(system_id=self._config.USERNAME, password=self._config.PASSWORD)
def _register_events(self):
print('Registering Smpp events')
self._client.set_message_sent_handler(self._config.ON_DELIVERED_CALLBACK)
self._client.set_message_received_handler(self._config.ON_RECEIVED_CALLBACK)
def send_message(self, message: str):
print('Sending SMS message to target: ' + self._config.TARGET)
parts, encoding_flag, msg_type_flag = smpplib.gsm.make_parts(message)
for part in parts:
self._client.send_message(
source_addr_ton=smpplib.consts.SMPP_TON_INTL,
source_addr_npi=smpplib.consts.SMPP_NPI_ISDN,
source_addr=self._config.SOURCE,
dest_addr_ton=smpplib.consts.SMPP_TON_INTL,
dest_addr_npi=smpplib.consts.SMPP_NPI_ISDN,
destination_addr=self._config.TARGET,
short_message=part,
data_coding=encoding_flag,
esm_class=msg_type_flag,
registered_delivery=True,
)
I am not sure if it's an expected behaviour of the library or a limitation. I have tried the find the documentation for this lib but could not find anything other than this.
Please advise if you experience a similar issue any work around possible or if this is expected behaviour in SMPP protocol (which very unlikely).
Update:
I found the limitation in the source code:
class BindTransmitter(Command):
"""Bind as a transmitter command"""
params = {
'system_id': Param(type=str, max=16),
'password': Param(type=str, max=9),
'system_type': Param(type=str, max=13),
'interface_version': Param(type=int, size=1),
'addr_ton': Param(type=int, size=1),
'addr_npi': Param(type=int, size=1),
'address_range': Param(type=str, max=41),
}
# Order is important, but params dictionary is unordered
params_order = (
'system_id', 'password', 'system_type',
'interface_version', 'addr_ton', 'addr_npi', 'address_range',
)
def __init__(self, command, **kwargs):
super(BindTransmitter, self).__init__(command, need_sequence=False, **kwargs)
self._set_vars(**(dict.fromkeys(self.params)))
self.interface_version = consts.SMPP_VERSION_34
As you can see the BindTransmitter contructor (__init__) truncates the system_id to a max length of 16 and passsword to 9. Not sure why this was done this way.

Answer 1

I checked the official SMPP protocol spec. According to the spec the system_id is supposed to max 16 and password is supposed to be 9 for connection type: transmitter.
The following is the screenshot of this spec:
This is the link to the spec if anyone is interested.
So in conclusion, the library implementation of the spec is correct.