code: @Override
    public String getRealmForPeer(String fqdn) {
      //
      Collection<Realm> realms = getRealms();
      for (Realm r : realms) {
        IRealm ir = (IRealm) r;
        if (ir.hasPeerName(fqdn)) {
          return ir.getName();
        }
      }
      return null;
    }
docs: /*
  (non-Javadoc)
  @see org.jdiameter.client.api.controller.IRealmTable#getRealmForPeer(java.lang.String)