ssh: connect to host darkstar port 22: Connection refused

Hello,

I get this message when I try to connect to darkstar (a laptop with wifi) from computer A. But I can connect to darkstar from B, and even from A through B.
A and darkstar have exactly the same installed packages (slackware64-current), the .new files have been treated. I have also tried to remove all the ~/.ssh/known_hosts

it is also impossible to connect to A from darkstar