Who I have the same questioned this topic

I am using Message+ on both Window PCs and Android phones.  It works fine when I directly connect to the Internet on the incoming internet line provided by Optimum to my house.  However if I connect after my microtik  router it no longer is able to synchronize (all devices).  This router has no problem with regular Skype voice, internet or outgoing VPN connections so the problem is presumably  specific to the protocol.  This router is providing SRC (and dest NAT).  To debug this I would like to know what protocol and ports are used by Message+. 

I'm assuming it be handled via SRC NAT.

thanks

Keith R