code: protected void connectionClosed (Connection conn)
      {
          // remove this connection from our mappings (it is automatically removed from the Selector
          // when the socket is closed)
          _handlers.remove(conn.selkey);
          _connections.remove(conn.getConnectionId());
          _oflowqs.remove(conn);
          synchronized (this) {
              _stats.closes++;
          }
      }
docs: Called by a connection when it discovers that it's closed.