Hi @riomus, this project was an experiment @jroper did. The README file states:

The Play backed socket.io support library is Incubating.

However, any PR and improvements are welcome. If the community sees value in it and push it forward, then it gets out of "incubating" stage.

@renatocaval is right, furthermore, it's not likely that this will ever be an officially supported by Lightbend project. But that doesn't mean that it won't be maintained, as long as people find it useful, people are likely to submit fixes etc. We use it ourselves at Lightbend, so we'll be maintaining it as the need arises for ourselves. Upgrading to Play 2.7 is certainly a good thing, so a PR that provides Play 2.7 support will certainly be welcomed. I don't think cross building against Play 2.6 and 2.7 is a big need, I don't anticipate that there'll be any changes to the API that would warrant maintaining them both together in the same branch, rather, we can bump the version to 2.x, that branch will be built against Play 2.7, and maintain a 1.x branch for Play 2.6, so bug fixes can still be backported if necessary.

@jroper what do you think about supporting multiple play versions in the same way as in reactivemongo? Cross building with separate source roots for implementations that must differ? I think that in this way it would be more nice and easy to maintain

That's only worth it if we expect to make changes that we'll want applied to both versions. There is no development planned for play-socket.io, so no changes expected, so setting up cross building is not going to have any value.

@riomus, I would like to add one more thing on top of what @jroper said.

Considering that this project gets some traction, it will be community driven. As such, it's important to keep it small and minimize any friction. If we have built for Play 2.6.x and 2.7.x, it means more work, more maintenance and increases the risk that one, probably 2.6.x, start to lag behind.

I would recommend to start small. Bring in the changes you need and let it grow organically. If there is a real need to evolving a 2.6.x branch, then someone in the community will do it. Chances are that people will prefer to move to 2.7.x instead of maintaining an open source project themselves.

Don't put too much on your plate, because community driven projects are done in our free time and everybody lacks free time. It's the most scarce resources on the planet.

My 2cc.