Connection Problems using Matlab mongoc

Working with Data Drivers
1

Hi everyone,

I am facing problems to connect to a mongoDB container from Matlab using mongoc. I am able to connect using MongoDB Compass and pymongo with two different username/password combinations. The Python code looks as follows:

# Define MongoDB connection parameters
host = 'localhost'       # Hostname where MongoDB is running
port = 27017             # Port MongoDB is listening on
database_name = 'test'   # Database you want to connect to

# Define credentials
username = 'testUser'
password = 'testPassword'

# Construct the connection URI
uri = f'mongodb://{username}:{password}@{host}:{port}'

try:
    # Create a MongoClient object
    client = MongoClient(uri)
    
    # Access the database
    db = client[database_name]
    
    # Print a success message
    print('Successfully connected to MongoDB with authentication')
    
    # Optionally, check if you can list collections (as a simple test)
    collections = db.list_collection_names()
    print('Collections in the database:', collections)
    
except ServerSelectionTimeoutError as e:
    # Handle server selection timeout errors
    print('Failed to connect to MongoDB: Server selection timeout', e)
except ConnectionFailure as e:
    # Handle general connection failures
    print('Failed to connect to MongoDB: Connection failure', e)
except Exception as e:
    # Handle any other exceptions
    print('An error occurred:', e)

If I try to connect with Matlab I use

 conn = mongoc("localhost",27017,"test", "UserName", "testUser", "Password", "testPassword");

Unfortunately the obtained error Message just indicates that authentication fails:

Error using database.mongo.connection
[Mongo Driver Error]: Authentication failed..

Error in mongoc (line 52)
    conn = database.mongo.connection(varargin{:});

If I the other username/password I obtain the same error. I would highly appreciate any suggestions what to do.

All the best
Moritz

2

Hi @Moritz_H - welcome to the MongoDB community forums!

I am not a user of mongoc, but having a look at the docs, I think your syntax is slightly off. You wrote:

conn = mongoc("localhost",27017,"test", "UserName", "testUser", "Password", "testPassword");

… but I think it should be:

conn = mongoc("localhost",27017,"test", UserName="testUser", Password="testPassword");

That’s from the MathWorks docs

3

I am a Python developer, and I wanted to point something out, in case it’s confusing later!

PyMongo is super-lazy, so it doesn’t connect to the server when you think it does.

# Create a MongoClient object - DOES NOT CONNECT TO SERVER
client = MongoClient(uri)
    
# Get a database object - DOES NOT CONNECT TO SERVER
db = client[database_name]

# DOES CONNECT TO THE SERVER (because it actually needs to get the list of collection names in the database)
collections = db.list_collection_names()

In this case, if you left out the call to list_collection_names then your uri could be wrong, and you’d never know because PyMongo isn’t even going to attempt to connect to your server. Hope this helps!

Mark

4

Thanks for the helpful advice :slight_smile:

5

Thanks Mark. I found both ways to implement online and they throw a similar error.