tunnel is a reverse proxy for exposing local web servers to the outside world via SSH. It is a minimal self-hosted tool in the tradition of web services like ngrok, localtunnel, and Serveo. Like Serveo, it only requires an SSH implementation on the client; like localtunnel, it is free software.
A toy installation of tunnel running on localhost can be started and tested like this:
# get it
go get github.com/alexshpilkin/tunnel
# generate a host key
ssh-keygen -f ssh_host_key -t rsa -N ''
# launch the server
tunnel --bind-ssh 2222 --bind-http 8080 --authorized-keys ~/.ssh/authorized_keys
# forward test.localhost to localhost:8000
ssh -fN -R test.localhost:0:localhost:8000 -p 2222 localhost
# launch an HTTP server on localhost:8000
python -m http.server
# see the result!
curl -H 'Host:test.localhost' http://test.localhost:8080/
This may seem a bit underwhelming, but running tunnel on localhost is kind of pointless. Normally, you’d want to set it up behind a TLS terminator with a wildcard certificate and a reverse proxy so that it can give out *.yourdomain instead of *.localhost, and expose it on port 80 or 443 so that fiddling with the Host header is not necessary. The key point is that once a tunnel instance has been set up at SERVER, you can use
ssh -N -R DOMAIN:0:HOST:PORT SERVER
to expose HOST:PORT under DOMAIN.