code: public final TcpClient doOnDisconnected(Consumer<? super Connection> doOnDisconnected) {
  		Objects.requireNonNull(doOnDisconnected, "doOnDisconnected");
  		return new TcpClientDoOn(this, null, null, doOnDisconnected);
  	}
docs: Setup a callback called after {@link Channel} has been disconnected.
  
  @param doOnDisconnected a consumer observing disconnected events
  
  @return a new {@link TcpClient}