class type connection_cache =object..end
method get_connection_state : Unix.file_descr -> conn_stateReturns the state of the file descriptor, or raises Not_found
method set_connection_state : Unix.file_descr ->
       peer -> conn_state -> unitSets the state of the file descriptor. It is allowed that
 inactive descriptors are simply closed and forgotten. It is
 also possible that this method raises Not_found, leaving it
 to the caller to close the connection.
method find_inactive_connection : peer ->
       transport_layer_id ->
       Unix.file_descr * inactive_dataReturns an inactive connection to the passed peer, or raise
 Not_found. Since Ocamlnet-3.3, the required transport ID
 is also an argument of this method. Since Ocamlnet-4, the
 inactive_data record is also returned.
method find_my_connections : <  > -> Unix.file_descr listReturns all active connections owned by the object
method close_connection : Unix.file_descr -> unitDeletes the connection from the cache, and closes it
method close_all : unit -> unitCloses all descriptors known to the cache