In dev mode the Boundary server is going to listen on localhost only by default, so you won’t be able to access it from outside the host at all regardless of firewall settings. If you want to run it on a remote host you’ll need to set the address flag for the API listener (either in a config file or on the command line) to an interface assigned IP, or 0.0.0.0.
If you intend to run workers on other hosts, you’ll also need to set the public cluster address of the control server to an address the workers can reach it on, and set the public address of the workers to an address the clients can reach the workers on (usually a public IP).