I used the command “ifconfig” to check the IP address of Vim4. In the first I use another PC with Ubuntu to connect vim4, it’s successful. Then I use Macbook to connect Vim4 with ssh, it’s failure. But I can use Macbook to connect the Ubuntu PC. So I don’t know what is the problem.
I have used the command to install ssh. but it doesn’t work. maybe just like you say, the default version of ssh have a problem. In work days I try to uninstall ssh and install again. It’s a good idea thanks!