Solving the MongoDB Connection Error: Can't Connect to 127.0.0.1:27017 After Port Change

Описание: Learn how to fix the MongoDB connection error when changing the default port from `27017` to `27042`.
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This video is based on the question https://stackoverflow.com/q/67584758/ asked by the user 'jeyremd' ( https://stackoverflow.com/u/15960611/ ) and on the answer https://stackoverflow.com/a/67584825/ provided by the user 'Đăng Khoa Đinh' ( https://stackoverflow.com/u/15527686/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the MongoDB Connection Error

If you've ever tried changing the default port of your MongoDB server and encountered an error, you are not alone. One common issue arises when you attempt to connect to the database only to receive the dreaded message:

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This issue typically indicates that MongoDB is listening on a different port than the one you are trying to connect to. In this post, we’ll explore why this error occurs and how to fix it easily.

Why the Error Happens

When you modify the MongoDB configuration file (mongod.conf) to change the listening port, it’s important to recognize that the mongo shell still defaults to connecting to port 27017. If MongoDB is listening on a different port, such as 27042, your connection attempt will fail, resulting in the error you see.

Steps That Led to the Error

Here’s a recap of the steps that might have led you to this predicament:

You edited the configuration file located at /etc/mongod.conf to set the new port:

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You restarted the MongoDB service with:

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Tried to connect using the default command:

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Encountered the connection error.

How to Fix the Error

Step 1: Connecting to the Correct Port

To resolve the issue, you simply need to specify the new port in your connection command. Instead of just running mongo, execute the following command:

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This directs your connection to the suitable port where MongoDB is actively listening.

Step 2: Verification

To ensure that your changes are effective, you can check the status of the MongoDB service:

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Look for any notices about errors or issues in the service logs. This can provide clues if something went wrong during the service start.

Step 3: Optional - Setting Up Aliases

If you find yourself frequently connecting to the same non-default port, you might want to set up an alias in your shell configuration file (like .bashrc or .bash_profile). Add this line:

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After saving and sourcing the file (by running source ~/.bashrc or source ~/.bash_profile), you can just type mongo42 next time you want to connect.

Conclusion

By understanding the relationship between MongoDB's configured port and the connection commands, you can easily troubleshoot connection issues. This error is primarily due to mismatched ports, and by specifying the correct port with your connection command, you can avoid the frustration of connection failures.

If you've encountered similar issues or found additional solutions, feel free to share your experiences and insights in the comments!