how to get parameter in shiny server?

I try code

ui <- fluidPage(
  h3("URL components"),
  verbatimTextOutput("urlText"),

  h3("Parsed query string"),
  verbatimTextOutput("queryText")
)

server <- function(input, output, session) {

  # Return the components of the URL in a string:
  output$urlText <- renderText({
    paste(sep = "",
      "protocol: ", session$clientData$url_protocol, "\n",
      "hostname: ", session$clientData$url_hostname, "\n",
      "pathname: ", session$clientData$url_pathname, "\n",
      "port: ",     session$clientData$url_port,     "\n",
      "search: ",   session$clientData$url_search,   "\n"
    )
  })

  # Parse the GET query string
  output$queryText <- renderText({
    query <- parseQueryString(session$clientData$url_search)

    # Return a string with key-value pairs
    paste(names(query), query, sep = "=", collapse=", ")
  })
}

shinyApp(ui, server)

http://example.com/?examplecode=1

I want data : examplecode=1

but I get url_search value : ?w=&__subapp__=1

How to I get url_search?

I'm r newbie.... thanks