The connection string for azure cosmosdb emulator is the following:

mongodb://localhost:C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw==@localhost:10255/admin?ssl=true

But it seems like pymongo is not parsing it properly.

Here's my code:

import pymodm
CONN_STR = "mongodb://localhost:C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw==@localhost:10255/admin?ssl=true"
pymodm.connection.connect(CONN_STR)

And I get this error:

Traceback (most recent call last):
{{ File "test.py", line 3, in <module>}}
{{ pymodm.connection.connect(CONN_STR)}}
{{ File "....virtualenvs\env-YN3\lib\site-packages\pymodm\connection.py", line 63, in connect}}
{{ parsed_uri = uri_parser.parse_uri(mongodb_uri)}}
{{ File "....virtualenvs\env-YN3\lib\site-packages\pymongo\uri_parser.py", line 424, in parse_uri}}
{{ nodes = split_hosts(hosts, default_port=default_port)}}
{{ File "....virtualenvs\env-YN3\lib\site-packages\pymongo\uri_parser.py", line 260, in split_hosts}}
{{ nodes.append(parse_host(entity, port))}}
{{ File "....virtualenvs\env-YN3\lib\site-packages\pymongo\uri_parser.py", line 155, in parse_host}}
{{ % (port,))}}
ValueError: Port must be an integer between 0 and 65535: C2y6yDjf5

It does work whenever I specify the username and password directly, though, so it appears to be a problem with the pymongo connection string parser. The following code works fine:
host = "mongodb://localhost:10255/cm?ssl=true"
user = "localhost"
password = "C2y6yDjf5/R+ob0N8A7Cgv30VRDJIWEHLM+4QDU5DE2nQ9nDuVTqobD4b8mGGyPMbIZnqyMsEcaGQy67XIw/Jw=="
pymodm.connection.connect(host, username=user, password=password)