code: func (srv *endlessServer) getListener(laddr string) (l net.Listener, err error) {
  	if srv.isChild {
  		var ptrOffset uint = 0
  		runningServerReg.RLock()
  		defer runningServerReg.RUnlock()
  		if len(socketPtrOffsetMap) > 0 {
  			ptrOffset = socketPtrOffsetMap[laddr]
  			// log.Println("laddr", laddr, "ptr offset", socketPtrOffsetMap[laddr])
  		}
  
  		f := os.NewFile(uintptr(3+ptrOffset), "")
  		l, err = net.FileListener(f)
  		if err != nil {
  			err = fmt.Errorf("net.FileListener error: %v", err)
  			return
  		}
  	} else {
  		l, err = net.Listen("tcp", laddr)
  		if err != nil {
  			err = fmt.Errorf("net.Listen error: %v", err)
  			return
  		}
  	}
  	return
  }
docs: /*
  getListener either opens a new socket to listen on, or takes the acceptor socket
  it got passed when restarted.
  */