scp: how to transfer files between two computers that do not communicate directly.
Scenario: you want to transfer files between two computers, the remote1 and remote2 computers that cannot establish a between connection due to firewall restrictions, but you can scp both computers from a third computer.
If the third computer can scp both computers remote1 and remote2 then you can use the “-3” parameter which allows you to transfer files using the third computer as a proxy.
thirdcomputer$ scp -3 user1@remote1:/home/user1/file1.txt user2@remote2:/home/user2/file1.txt
short and sweet! ;)