The remote Linux computer is in an internal network and has no public IP address. So I installed ngrok.
ngrok tcp 22
ngrok by @inconshreveable (Ctrl+C to quit) Tunnel Status online
Version 2.0.19/2.0.17
Web Interface http://127.0.0.1:4040
Forwarding tcp://0.tcp.ngrok.io:36428 -> localhost:22
Connections ttl opn rt1 rt5 p50 p90
0 0 0.00 0.00 0.00 0.00
I checked that sshd is running.
At the local PC, I tried
ssh myuser@ngrok.com -p36428
which gave rise to
ssh: connect to host ngrok.com port 36428: Connection refused
You are connecting to the wrong destination address. The command should be
ssh myuser@0.tcp.ngrok.io -p36428
Notice the different hostname (ie 0.tcp.ngrok.io instead of ngrok.com).
And generally you would want to put the user@hostname after all the options (eg -p36428), even though it doesn't generally cause any issues.
来源：https://stackoverflow.com/questions/30577729/unable-to-ssh-into-remote-linux-by-ngrok