code: func setListenAddress(ctx *cli.Context, cfg *p2p.Config) {
  	if ctx.GlobalIsSet(ListenPortFlag.Name) {
  		cfg.ListenAddr = fmt.Sprintf(":%d", ctx.GlobalInt(ListenPortFlag.Name))
  	}
  }
docs: // setListenAddress creates a TCP listening address string from set command
  // line flags.