Passing the Port is a tradition that believed to come from the British Navy.
The decanter is placed in front of the host who serves the guest on their right.
Then they put the decanter in front of the guest on their left (you never serve yourself).
This continues until the makes it way back to the host.
If it doesn’t make its way back to the host, it is impolite to ask for it directly. Instead the host asks the individual nearest the decanter if they know the bishop of Norwich or another village in England.
The person should not answer the question but should immediately pass the port.
If they answer the question with a “No”, they are told that “the bishop is an awfully good fellow, but he never passes the port!" which will hopefully bring to his attention that he is hogging the decanter.
When the Port is decanted at a table, it should be finished in one sitting.