localtunnel | Expose localhost servers to the Internet

Does this 400 error occur when testing IPN in sandbox mode? If so, the issue is related to PayPal's recent sandbox migration to the cloud. For now, change the sandbox postback verification hostname from ipnpb to www:

Update: This answer only partially solved the issue.

Using tcpdump on the server, I found that the server is indeed receiving data (even though Lumen was saying that it was not receiving data), and the amount of data seemed to correspond with whether a file is attached or not. From this, it seemed the problem was occurring with Apache, PHP, or Lumen.

I also enabled mod_dumpio, and tested the requests with and without a file and both appear to send data normally. The file request was clearly sending a large amount more, and the Content-Length reported seemed accurate, even though Lumen was reporting no data.

Sorting through error.log I did find the error, however. It was just that PHP was dropping the data because it exceeded the post_max_size size of 8MB. Once editing php.ini for that and upload_max_filesize, the application worked fine.

What's funny is that's usually the first error that occurs with file uploads and PHP servers, so it's weird I didn't suspect it. It would be nice if PHP issued a 413 Response by default.

your local network must have some gateway/router connecting it to the internet - if it's a home network, probably integrated with your cable/dsl/fiber modem or attached router. This gateway holds the public IP of your connection to the internet. It will be to this IP your public connections will need to connect.

You can configure your network's router to port forward incoming connections on a given port to the internal address of your server. Keep in mind that this means it's open to the wide internet.

I found the solution for my problem. Looks like you first need to access to the dynamic url serving your backend and click on "Continue". After doing that, CORS won't be a problem anymore.

You can use https://github.com/Miserlou/Zappa to deploy your flask-ask application.

Tutorial available here : AWS Alexa deploy on aws lambda using zappa

If you are absolutely certain that you solved all vulnerabilities you'd like to skip the audit, you can do so by appending --no-audit.

npm install --no-audit

or npm will fix for you

npm audit fix

But this will update version of modules. Which might lead to breaking of code.

It could be a problem with localtunnel or your localtunnel connection, maybe involving SSH. You could run DEBUG=* npx localtunnel -p 8000 and see if you get an error message.

FWIW, I am currently getting the message localtunnel:client tunnel server offline: unable to verify the first certificate, and it is not returning the subdomain.

If you expose your database to the world with a weak password for a database superuser, that will definitely lower your security in a substantial way. Hackers routinely patrol for such weak settings and exploit them, mostly for cryptocurrency mining but also to add you to botnets. In those cases they don't care about your database itself, it is just a way in to get at your CPU/network connection. They might also probe for valuable information appearing in your database, in which case they don't even need to be a superuser.

If you always run the latest bugfix version and use a strong password (like the output of pwgen 20 -sy -1) and use SSL or if you correctly use some other method of authentication and encryption, then it will lower security by only a minimal amount.

If you personally control every password, and ensure they are strong, and test that they are configured correctly to be required for log on (e.g. intentionally enter it wrong once to make sure you get rejected), I wouldn't worry too much the port forwarding providing bad guys access to the machine. If you care about people being able to eavesdrop on the data being sent back and forth, then you also need SSL.

Encrypted tunnels of course are another solution which I am not addressing.