I have two machines; referring to them as A and B respectively. They are on different subnets. However, I can ssh to B from A. But the reverse is not possible. Therefore from A I can access a service hosted on B via port forwarding. Is there some way to do the reverse, i.e. access a web server hosted on A (or some other service) from B?

Never mind I found the answer. I can do reverse port forwarding via ssh tunneling.