How to extract values from html script in server.R - shiny-server

Question

I try to build an app that let's users select rectangles on a google Map. The coordinates should than be extracted and used for further calculations. I found an excellent tutorial here on how to interact with the google api and send the data to R. However, I needed to modify the files a bit to have a costum ui.R that lets the user select the fields but also select other options important for processing.
So now I have three files in the same directory.
The html file with the javascript commands for the google api, the ui.R and the server.R.
index.html
content can be found in the link above but the important part is:
//This function listen to the drawing manager and after you draw the rectangle it extract the coordinates of the NE and SW corners
google.maps.event.addListener(drawingManager, 'rectanglecomplete', function(rectangle) {
var ne = rectangle.getBounds().getNorthEast();
var sw = rectangle.getBounds().getSouthWest();
//The following code is used to import the coordinates of the NE and SW corners of the rectangle into R
Shiny.onInputChange("NE1", ne.lat());
Shiny.onInputChange("NE2", ne.lng());
Shiny.onInputChange("SW1", sw.lat());
Shiny.onInputChange("SW2", sw.lng());
ui.R
I use tags$embed to embed the index.html file in ui.R
require(shiny)
shinyUI(
fluidPage(
titlePanel("Included Content"),
# mainPanel(
fluidRow(
column(9,
div(style='height:800px; width:1200px; overflow: hidden',
tags$embed(src="./index.html", seamless=FALSE,width="100%",height="100%"))),
column(3,
h2("Some Calculations"),
selectInput("Test",label=NA,choices=c("yes","no")),
selectInput("Test2",label=NA,choices=c("2","3")),
h3("Coordinates"),
tableOutput("test"),
h3("allInput"),
tableOutput("test2"))
)
))
server.R
# server.R
library(sp)
library(rjson)
library(shiny)
library(dplyr)
library(tidyr)
shinyServer(function(input, output,session) {
CorLongLat<<-reactive({
if(length(input$NE1)>0){
as.data.frame(matrix(c(input$NE2,input$NE1,input$NE2,input$SW1,input$SW2,input$SW1,input$SW2,input$NE1),ncol=2,byrow=T))
}
})
output$test<-renderTable({
CorLongLat()
})
output$test2<-renderTable({
as.data.frame(reactiveValuesToList(input))%>%gather(ID,Value)
})
})
However, if I try to disply all inputs via output$test2<-renderTable({
as.data.frame(reactiveValuesToList(input))%>%gather(ID,Value)
})
it showes only the controls that are directly embeded in the ui.R. How do I access the variables NE1,NE2,SW1,SW2 from index.html that are created via Shiny.onInputChange?
EDIT
In the meantime I got a little closer to the core of the problem. Running the App with options(shiny.trace=TRUE) tells me after launching the app the following
Listening on http://127.0.0.1:4840
SEND {"config":{"workerId":"","sessionId":"16000363ddc17409cd5fdf25c038b61d"}}
RECV {"method":"init","data":{"Test":"yes","Test2":"2",".clientdata_output_test4_hidden":false,".clientdata_pixelratio":1,".clientdata_url_protocol":"http:",".clientdata_url_hostname":"127.0.0.1",".clientdata_url_port":"4840",".clientdata_url_pathname":"/",".clientdata_url_search":"",".clientdata_url_hash_initial":"",".clientdata_singletons":"",".clientdata_allowDataUriScheme":true}}
SEND {"errors":[],"values":[],"inputMessages":[]}
SEND {"config":{"workerId":"","sessionId":"0881062c26c882de2d0648a96ed98296"}}
RECV {"method":"init","data":{".clientdata_output_json_hidden":false,".clientdata_pixelratio":1,".clientdata_url_protocol":"http:",".clientdata_url_hostname":"127.0.0.1",".clientdata_url_port":"4840",".clientdata_url_pathname":"/index.html",".clientdata_url_search":"",".clientdata_url_hash_initial":"",".clientdata_singletons":"",".clientdata_allowDataUriScheme":true}}
SEND {"errors":[],"values":[],"inputMessages":[]}
After selecting a triangle on the map I get
RECV {"method":"update","data":{"NE1":67.40748724648756,"NE2":-11.77734375,"SW1":62.552856958572896,"SW2":-26.9384765625}}
And after selecting on selectInput :
RECV {"method":"update","data":{"Test2":"3"}}
I think the problem here is the second sessionID that is established. How do I refer to those in server.R or how do I combine both into on?