Xpra v2.2 came out a few weeks ago. It is incompatible with 2.0, so please, update the port, as I can't use xpra on freebsd anymore, as it is update on other hosts to 2.2.
Xpra 2.1.1, released August 8, is the most recent version. There is no 2.2 release yet nor do I expect one soon considering it hasn't even been a whole month since the release of 2.1.0. I am working on updating the port but it is not yet ready. Xpra 2.1.1 is currently working as a client but not as a server. There should be no compatibility problems with mixed versions. I tested Xpra 2.1.1 as a client with a Xpra 2.0.3 server during my recent update work. According to the project page (https://www.xpra.org/trac/wiki/Versions) Xpra 2.x is compatible back to v1.0.
Turns out you are right, I probably have installed beta/alpha on ubuntu. I downgraded there anyways. Well, xpra doesn't support FreeBSD anyways, so I guess there's no point in tickets.