Who is the Porter but none other than the Spirit. John 1:33-34 records that he saw the Spirit descending like a dove and remaining on Christ (Jesus). This is John’s introduction of Jesus the Good Shepherd so the Holy Spirit (Porter) opening for the good Shepherd.
Then there is the fact that the true sheep hear Him. We have the term “His own sheep” meaning they are His. It says He leads them out. There we have a fact that someone who does not follow Him must not be His sheep, perhaps just religious, but not His.
Jesus then says, “I am the door of the sheep”. We can’t enter the sheepfold without going through the door. Anyone who tries another way is a thief. The good Shepherd gives His life for the sheep.
Then there is the hireling. One who is just preaching for a living. For him I would say preach Christ! I have never made oodles of money preaching the Word of God. When going gets tough they are gone and what happens to the sheep? They are scattered. Some never come back.