I have remote Linux server behind NAT, without ability to forward ports. All outbound ports are open though. I need to be able to connect to OpenVPN & SSH ports on this server from arbitrary PCs / mobile devices which all have dynamic & unpredictable IP. What is the best approach to achieve that?
If needed, I can use another public Linux server where I control all ports to assist in establishing the connection, but ideally I would want a way to establish direct connection without passing traffic through intermediate proxy.
I am interested in the most standard/robust method. It might be known technique, but it seems I don't know proper keyword to search.