In scripture this word is used in the sense of doorkeeper. The Levites kept the doors of the temple: it was an honorable office (2 Sam. 18:26; 2 Kings 7:10-11; 1 Chron. 9:17-26; Mark 13:34).
In John 10:3 the Porter is the Spirit of Jehovah working in Israel, who recognized the Lord Jesus as entering in by the door into the sheepfold that as the Good Shepherd He might have access to the sheep.