HTTP Tunneling

Consider the following setup:

I have a normal web browser running on computer A.

I have a web server running behind a firewall on computer B. With no way
of opening a port.

I have another server (computer C) that is wide open to the internet...
Is it possible to get computers A and B to communicate by running some
kind of software on computer C to forward requests back and forth?

OR, is there any other way to get computers A and B to talk?

Thanks