The SSH connection is often disconnected automatically for security reasons after several minutes of inactivity. You can change the command to keep the echo connected.
Please enter/etc/ssh/ssh_ Add or modify the following lines in the config file.
[ root@localhost ~]# vim /etc/ssh/ssh_ config
ClientAliveInterval 3600
ClientAliveCountMax 3
Save Exit
Restart the sshd service
systemctl restart sshd