how to close the connection when exiting the shiny app

Question

I make shiny app with websocket connection, and want close connection, when i exiting (stop) my shiny app. I have a suggestion that function on.exit() can solve my problem, but I do not know where to use it in shiny app. Are there any other ways to close the connection when the application stops?

score 2 · Accepted Answer · answered Feb 01 '21 at 15:15

You can use session$onSessionEnded for this purpose. Once the session ended the code inside will run. For example:


library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(

    # Application title
    titlePanel("Old Faithful Geyser Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
            sliderInput("bins",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30)
        ),

        # Show a plot of the generated distribution
        mainPanel(
           plotOutput("distPlot")
        )
    )
)

# Define server logic required to draw a histogram
server <- function(input, output) {

    output$distPlot <- renderPlot({
        # generate bins based on input$bins from ui.R
        x    <- faithful[, 2]
        bins <- seq(min(x), max(x), length.out = input$bins + 1)

        # draw the histogram with the specified number of bins
        hist(x, breaks = bins, col = 'darkgray', border = 'white')
    })
    
    session$onSessionEnded(function() {

        # you can put your code here to close the connection
    })
}

# Run the application 
shinyApp(ui = ui, server = server)

how to close the connection when exiting the shiny app

1 Answers1