Fishin' to the end, Oc.P
No treats at all. Do not let him greet friends at the door...put him outside or in another room. Once your friends are sitting let him in to socialize....he's either overly protective or feels threatened....probably the latter. This is crucial: when the dog approaches company, have them put their arms down with palms out. This allows the dog to smell without feeling threatend. Don't let anyone try to pet him unless the dog tells you it's OK. It will take time and patience but it will work.