invalidateLater for incrementing values

I have a Shiny app which among other functionalities, allows the user to click on a leaflet map,captue the lat lon as the coordinates of a ship, feed in the course and speed and pass this information on to a radar simulator over a socket. Given the course and speed of the ship,I need to pass on the updated coordinates to the radar simulator every second. Presumably, invalidateLater() is what I need after reading through this. But somehow I just can't wrap my head around the functioning of invalidateLater() . This is what I have unsuccessfully tried so far:

#Reactive values to hold the lat lon of the map_click event
rvs <- reactiveValues()

  #Data to be passed to the simulator
  df <- data.frame(Type='Platform',ID='Own_Ship',Lat = rvs$own_ship_lat,
                   Lon = rvs$own_ship_lon,
                   Alt=10.5, LandReflect = 10,

  #Convert the data to json format
  jdata <- jsonlite::toJSON(df)

  #Function to make a socket connection and pass on the json data to the simulator

  #Calculate next point to be passed on to the simulator
  next_pt <- geosphere::destPoint(c(rvs$own_ship_lon, rvs$own_ship_lat), 
                       input$own_course, input$own_speed)

    isolate(rvs$own_ship_lat <- next_pt[2])
    isolate(rvs$own_ship_lon <- next_pt[1])
    # print(next_pt)


rvs$own_ship_lat and rvs$own_ship_lon hold the lat lon values of the mouseclick on the leaflet map. If I uncomment the the print(next_pt) , it infinitely prints the first rightly calculated next_pt values.

You might find this article on invalidateLater() helpful. - Tom

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