If the machine you want to pull from is accessible via ssh, you can add the repository on it as a remote via ssh, and then pull from it like you would any remote:
$ git remote add repo_b username@host:path/to/repository.git
$ git pull repo_b master
(You can skip the step of adding a remote and just specify the full URL in the git pull command instead of a remote name, but if you’re going to be pulling from the repository on a regular basis, adding it as a remote will save you lots of typing.)