The error message "getaddrinfo ENOTFOUND undefined" in Node.js typically occurs when the dns.lookup or a similar network-related function tries to resolve a hostname or IP address, but the hostname is undefined.

Here are a few common scenarios that can trigger this error and possible solutions:

  1. Undefined Hostname Variable: If you are using a variable to hold the hostname or IP address, ensure that the variable is defined and has a valid value. For example:

    javascript
    const hostname = 'example.com'; // Valid hostname or IP address dns.lookup(hostname, (err, address) => { if (err) { console.error(err); } else { console.log('Resolved address:', address); } });

    Make sure your hostname variable has a valid value and is not undefined.

  2. Typo in the Hostname Variable: Check for typos or syntax errors in the variable name that holds the hostname. For example:

    javascript
    const hostName = 'example.com'; // Correct variable name is hostname, not hostName dns.lookup(hostname, (err, address) => { // ... });

    Ensure that the variable name is spelled correctly and matches the one used in the dns.lookup function.

  3. Async Code Execution: If you are working with asynchronous code, ensure that the dns.lookup function (or any other network-related function) is not being called before the variable holding the hostname is defined. For example, if you are fetching the hostname from a database or an external API, make sure that the variable is set before using it in the network-related function.

  4. Incorrect Usage of the dns.lookup Function: Double-check how you are using the dns.lookup function. The function expects a string representing the hostname or IP address as its first argument. If you are passing an object or an array instead of a string, it can lead to this error.

If you are still facing the issue after verifying the above points, inspect your code to determine the exact line where the error is occurring and check the value of the hostname variable at that point. Debugging and console logging can be helpful in identifying the root cause of the issue.

Remember that ENOTFOUND generally indicates that the DNS resolution failed, so you should focus on the hostname or IP address that you are passing to the network-related function and ensure it is valid and properly defined.

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