Unreachable docker daemon using TCP

Hi,

I have a docker daemon running on a machine A using a TCP socket :

dockerd -H tcp://0.0.0.0:2375 -l debug

When I try to interact with it on machine A, it works, e.g.:

docker -H tcp://X.X.X.X:2375 info

But if I try to do the same thing from machine B (!= A), I get something like:

Cannot connect to the Docker daemon at tcp://X.X.X.X:2375. Is the docker daemon running?

I have another docker daemon running on a unix socket on machine B, can this be an issue (if I specify -H)? Any idea how I can investigate this any further?