Friends Unable to Join My World

My friends are unable to join my Minecraft world with error "Unable to connect to world." The opposite, however, is not true. I am perfectly capable of joining my friends' worlds. No matter how many times I restart the world, restart the game, or even restart my computer, my friends (two playing on Windows 10, one playing on Xbox ONE) are completely unable to join my world in particular. We are all playing on the same version.