Yes you can. Go to his computer and turn it on and make sure the firewall is off and turn on a service. Seriously though, I would have to answer I don’t know because the question is too vague. It’s like me saying something like “my friend has a house down the block and he locked his doors and windows. Can I still get in?” You would probably answer “I don’t know. Maybe, it depends on the quality of his locks, etc…”
The very first thing I would recommend is you do a Google search and try and discover what a port is and really try and understand its function. Ask yourself questions like what makes a port open? Is a port part of the OS? What does a hacker attack? Does he attack a service or application or does he just attack a port? Does a port have value to a hacker if there is no service or application running? Is it possible to open a port with nothing running behind it and then access the computer? Simple questions like these.
Sure it would be so easy to tell you something like “Yeah, just go and download Port Opener utility from
www.youcantlockmeout.com and run it and you are in!" But if such a thing existed, what good would that really do if you don’t even know how a port functions? This is the way I was taught and I really feel it will pay off for you big time if you spend just a little time researching the basic principles. All I can say is that for me, the more I understand how things work and not just run things blind, the more I enjoy and love the entire process. I hope this makes some sense.