When I visit raspberry pi' ssh server on some places, I must set port forwarding on the home route, and set a dynamic DNS. If the route is not your's, you will helpless.

I think it may have another way, so I try ssh port forwarding ssh -CfNgR remote-port:localhost:local-port user@remote, then visit the remote-port.

The hole is an other way similar ssh port forwarding. On the global server create a holed, and the target host start hole. Last you can visit the holed to replace the real server.

The hole suit the situation: A(private) can connect B(global), C(private) can connect B, but B can't connect C, B can't connect A, and A can't connect C.

go get -v github.com/Lupino/hole/cmd/holed
go get -v github.com/Lupino/hole/cmd/hole

# Start on B
holed -addr=tcp://B-IP:B-PORT
# Start on C
hole -addr=tcp://B-IP:B-PORT -src=tcp://localhost:C-PORT
# On A just vist tcp://B-IP:B-PORT to replace visit C server

# A IP is 192.168.1.101
# B IP is 120.26.120.168
# C IP is 172.17.3.10

# Now on B server
holed -addr=tcp://120.26.120.168:4000

# On C server
hole -addr=tcp://120.26.120.168:4000 -src=tcp://127.0.0.1:22

# On A server
ssh root@120.26.120.168 -p 4000

# Now A can visit C via B server

go get -v github.com/Lupino/hole/cmd/hole-keys
hole-keys
holed -use-tls
hole -use-tls