localfileproxy

Proxy local files to an online url.

Very useful in web services that uses files on a user's computer but don't want to require the user to upload anything.

• supports many clients
• simple api for programmatic usage
• supports client machines that don't have exposed ports (e.g. a laptop)

Web Server, Client Service, Browser Client

It can be a bit confusing to follow how this works because there are multiple clients involved. Here are the three roles:

• web server (Broker): AKA the localfileproxy server, this is a server on the internet that has an exposed port
• client service (Service): The client application that has access to the files
• browser client (Requester): This is a service that has URLs to the web server, but because it's a browser (or a different computer than the local client) it can't access the files directly. It will request the files from the web server.

Technical Details

All of this is facilitated via a ZeroMQ Majordomo-like pattern. Roughly, this is what happens...

1. Start the Broker (the localfileproxy server on a Web Server)
2. Client Service (Service) registers itself itself with the Web Server (Broker), establishing a socket connection
3. Browser Client (Requester) makes request to Web Server (Broker)
4. Web Server (Broker) sends a request to the Client Service (Service) over the socket
5. Client Service (Service) answers the socket request with data from a file
6. Web Server (Broker) receives data from Client Service (Service), and passes it to the Browser Client (Requester)

The Broker uses a ZeroMQ Router. The Service uses a ZeroMQ Dealer.