Remote end hung up - newbie on OS X

I am trying to install packages/casks and just can’t - on OS X Catalina. Is this a firewall problem?

Cloning into ‘/usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask’…

remote: Enumerating objects: 12, done.

remote: Counting objects: 100% (12/12), done.

remote: Compressing objects: 100% (10/10), done.

error: RPC failed; curl 18 transfer closed with outstanding read data remaining

fatal: the remote end hung up unexpectedly

fatal: early EOF

fatal: index-pack failed

Error: Failure while executing; git clone https://github.com/Homebrew/homebrew-cask /usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask exited with 128.

This is a git error and is because there is a problem with your network.

Ok thanks. Not sure what that problem may be. More likely a router config issue. I opened port 9418 but maybe there is something else needs changing.

Thanks

That port was likely not the issue. Your connection was interrupted before it was done. With a closed port it wouldn’t have started at all.

Ok thanks - my router is set to not respond to ping requests so may be that but will see what other security options I have set that may be stopping it working.

Attempt to ping github, can you reach there?

Download “mtr” and type at a prompt “mtr github.com”, this will give you info on where the communication is breaking down at the layer 3 level if your having trouble reaching github.

With mtr I get zsh: command not found: mtr even though seemed to install ok. Do I need to enable root or use sudo or some other level of privilege? Is it just that the directory is not in my PATH?

I fixed it. It was my ISP DNS server - changed to 8.8.8.8 and it works fine now. Thanks all.