Multiplayer Issues

My friend and I have been trying to join each other's worlds for a few months now and nothing is working. He can't connect to any of my worlds, it always says unable to connect or keeps him at locating server. However, I can join his worlds for a few seconds until the game disconnects me. Most of the time when I do join his world I can see everything move but I can't interact with anything and my friend sees no movement from me. Please fix this ASAP!!