Start openssh-server in debug mode and listen on different tcp port:

  • copy openssh-server config file

    sudo cp -r /etc/ssh/sshd_config /tmp/sshd_config
    
  • set ssh sever listen port in new created config file

    vim /tmp/ssh/sshd_config
    
  • start ssh server in debug mode

    /usr/sbin/sshd -dD /tmp/ssh/sshd_config