Hacker usually has some kind of relay at hand: https://github.com/nwtgck/piping-server https://github.com/nwtgck/piping-server https://github.com/schollz/croc

Hacker usually has some kind of relay at hand: https://github.com/nwtgck/piping-server https://github.com/nwtgck/piping-server https://github.com/schollz/croc https://github.com/schollz/croc Or a NAT traversal tool: https://github.com/shawwwn/Gole https://github.com/shawwwn/Gole https://github.com/samyk/pwnat https://github.com/samyk/pwnat Or can just manually ncat simultaneously from both sides to proper addresses and ports, probably with the help of some public STUN server. Note that if worst case combination of NATs doesn't allow direct connection, then by definition a relay is needed, hacker or not, it doesn't matter.