public Collection<String> getIncomingServers() {
        return domainSessionsCache.keySet();
    }
Returns a collection with the domain names of the remote servers that currently have an
incoming server connection to this server.

@return a collection with the domains of the remote servers that currently have an
        incoming server connection to this server.
xmppserver/src/main/java/org/jivesoftware/openfire/SessionManager.java