I am having trouble understanding how ports work.
What I tried to do: I wanted to check if a particular port was open on my laptop. The port that i chose to check was the port used by bittorrent client for incoming connections. Let's say the port used by my bittorrent was 51346. I went to canyouseeme.org to check if that port was open. It showed an error.
Here is when the confusion started.
My bittorrent client is using the port without any issues. It was receiving data which means it must have been listening on that port. So, no firewall issues here. But why does cannyouseeme.org show me an error. I did check with other open port checker tools online. All show me the same error.
So, where am i going wrong? Why is it that I am not able to check if the port was open?
Extra Info (You can skip this if you want)
This is not the first time I am messing around with ports. I first tried to setup a public web server on my laptop with little luck. I had faced the same problem. I was running the server on port 80. But to the outside world, that port was closed. My idea was to access the web server with my public ip address. I tried it on a different port, didn't work. I setup port forwarding, still couldn't access the web server. Disabled windows firewall, didn't work. Initially I thought somehow my ISP is blocking all the ports which sounds ridiculous. I eventually gave up on trying to setup a public web server. Then I had to change my ISP and again gave the public web server idea a shot. Again failed. I still have no idea where I cam going wrong.
My current knowledge on how it all works: Any computer can access any other computer on the internet using the IP address. DNS only comes into the picture to translate the host name into an IP address. So, technically I should be able to access a web server setup on my laptop using my public IP address. But wasn't able to.
If you read till the end, thank you. Please correct me if my understanding of networks is flawed anywhere.
Edit: I am using Windows 10. But tried it with Windows 8.1 as well.
netstat -ano > net.txt
would be a good start.