Solve the problem that the virtual machine cannot be remotely connected through SSH service

I'm going through vscode Of ssh Service connection ubuntu When , Report errors ：

ssh: connect to host port 22: Connection refused

Here's the solution ：

One 、 install openssh-server service

sudo apt-get install openssh-server

Two 、 Install firewall

sudo apt-get install ufw

3、 ... and 、 Account opening firewall

sudo ufw enable

Four 、 Firewall permission 22 The port is open to the outside world

sudo ufw allow 22