To install Dukto in CentOS 7 then follow these commands. These commands are perfectly working in CentOS 7.
In this case you need to be a 'Root' user because you have to go to '/etc/yum.repos.d/' directory and this is only possible when you are 'Root' user.
So. first change your user to 'Root' in command line.
sudo wget https://download.opensuse.org/repositories/home:colomboem/CentOS_7/home:colomboem.repo
sudo yum update
sudo yum install dukto
After installing this you need to disable the firewall also for perfectly working. Please note disabling firewall only if you have a knowledge of firewall and its security features otherwise add its TCP protocol to firewall allowed list.