It is the same meaning as any TCP communication. We can choose which nodes will bind to a local address (including TCP port) so other node(s) can connect to it.
It is more common to have the primary node accepting connections from secondary nodes, because in this case we need to take care of router and firewall for just a single device. But it is also possible to have the primary node connecting to the secondary nodes. In this case it needs to know the address of the secondary nodes in advance.
Note that these configurations do not affect the role of each node. The primary node will be the one that will decide the order of transactions.