Im not sure if the host with one jj2 and join with the other jj2 window works for you, because it doesnt work for me and im able to host normally. The easiest way is to create a server with the name: SuPeR uLtRa CoOl TeSt HoTeL bY "insert name". Dont forget to add colors and you might want to add some gramar mistakes. Trust me if you are able to host people join a server with a name like that in 10 seconds or less.

And for the hosting problem itself: Some people also had those problems and posted the solution on this forum. Those who search will find the ultimate answer.