The master of every vessel, whether carrying passengers or not, when lying alongside any wharf shall fix, and at all times keep fixed, a safe and proper gangway from his vessel to the wharf. Every such gangway shall have side rails and stanchions, with ropes rove taut through same, the top rail or rope being not less than 2 ft 9 in high; and he shall also keep a gangway net properly secured beneath the gangway, and shall at all times throughout the night—that is to say, from sunset to sunrise—show and exhibit a proper light fixed at each gangway, and shall conform to and obey all orders the wharfinger may give regarding the position, size, and kind of the gangways and lights.