Android HttpURLConnection not passing data?

Question

Android

The connection comes to the computer, but the NodeJS server does not react to it in any way.
There are no problems with the server.

package com.ds.da.sensorsurvey

import android.os.AsyncTask
import java.io.BufferedOutputStream
import java.io.BufferedWriter
import java.io.OutputStream
import java.io.OutputStreamWriter
import java.net.HttpURLConnection
import java.net.URL


class CallAPI () : AsyncTask<String, String, String>() {

    override fun onPreExecute() {
        super.onPreExecute()
    }

    override fun doInBackground(vararg params: String): String? {
        val urlString = params[0] // URL to call
        val data = params[1] //data to post
        var out: OutputStream? = null

        try {
            val url = URL(urlString)
            val urlConnection = url.openConnection() as HttpURLConnection
            urlConnection.requestMethod = "POST"
            urlConnection.setRequestProperty("Content-Type", "application/json")
            out = BufferedOutputStream(urlConnection.outputStream)

            BufferedWriter(OutputStreamWriter(out, "UTF-8")).use{
                it.write(data)
                it.flush()
            }
            out!!.close()

            urlConnection.connect()

        } catch (e: Exception) {
            println(e.message)
        }
        return null
    }
}

Answer 1

I think that you first need to connect, and only then write data to the stream. IMHO, that's the problem.
Well, comments in general. AsyncTask should not be used for the network. This will end badly.
HttpUrlConnection has, as you can see, a very bad API.
It's better to take OkHttp and use it. It will be smarter and prettier. And more opportunities.