My question is the same as this one but hopefully adds clarity to get an answer. After reading this fantastic article on the specifics behind NAT Traversal along with a general summary of methods found here, I'm wondering if the scenario has been accomplished or is possible. I'm writing software that serves web pages on any specified port, and am wondering if it is possible to have a web client from the WAN side connect to this server that is behind a NAT router. The reason this I'm finding this difficult is because:
- I don't want to tell the user (who owns the web server) to configure their router to port forward (and many cases the user may not have privileges to do so).
- UPnP I believe is often default-disabled, and is another configuration privilege not afforded to the user.
- UDP Hole Punching looked promising until I realized the client is using a browser with http, and thus can communicate only through TCP, and limits my capability further by restricting options to browser-scripts.
- I haven not found a successful implementation of TCP Hole Punching, considering the difficulties of maintaining state information (currently I'm looking at chownat, but am wondering how to implement TCP over a UDP tunnel from a web browser (or if that's even possible?).
- Using a proxy to forward all traffic doesn't scale well (though using an external server, that is not behind a NAT, would be perfectly fine for setting up the initial connection or NAT traversal). By Scaling, I mean if many many users have their own web servers, not for the one user's web server to have high traffic (which is not a concern given the user's upload-bandwidth is often severely limited).
Right now I'm starting to think there will have to be some client-side browser script to help implement this, so the task won't be completely handled by the server. If anybody has any ideas or experience with trying to have a user connect to a web server behind a NAT router, I'd greatly help some direction! Thanks!
来源：https://stackoverflow.com/questions/22447215/http-tcp-connection-to-web-server-behind-nat