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After researches i still cant send a JSON POST request to a server.

I already tried some older answers:

Java - sending HTTP parameters via POST method easily

[Android]-POST Json with HttpUrlConnection

Post request for registering user data on server by HttpUrlConnection

Sending json object via http post method in android

How to send a JSON object over Request with Android?

My current code is:

FloatingActionButton btn_sendMsg = (FloatingActionButton) findViewById(R.id.btn_sendMsg);
    btn_sendMsg.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            /*Snackbar.make(view, "Sendevorgang...", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();*/
            createMsg();
private void createMsg() {
    Message message = new Message(txtbox_msg.getText().toString(), "testUser");
        AsyncT asyncT = new AsyncT();
        asyncT.execute(message);
AsyncT.java :
@Override
protected Message doInBackground(Message... params) {
    try {
        URL url = new URL("http://[ip]:[port]"); //in the real code, there is an ip and a port
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Content-Type", "application/json");
        conn.setRequestProperty("Accept","application/json");
        conn.setDoOutput(true);
        conn.setDoInput(true);
        conn.connect();
        JSONObject jsonParam = new JSONObject();
        jsonParam.put("uname", params[0].getUser());
        jsonParam.put("message", params[0].getMessage());
        jsonParam.put("latitude", "0");
        jsonParam.put("longitude", "0");
        jsonParam.put("id", "1");
        DataOutputStream os = new DataOutputStream(conn.getOutputStream());
        os.writeBytes(URLEncoder.encode(jsonParam.toString(), "UTF-8"));
        os.flush();
        os.close();
        Log.i("STATUS", String.valueOf(conn.getResponseCode()));
        Log.i("MSG" , conn.getResponseMessage());
        conn.disconnect();
    } catch (Exception e) {
    return null;
I'm getting the error code networkonmainthreadexception 500
How can i solve this?
                networkonmainthreadexception 500 is  may b causing because of server-side issues. You might check on to that.
– tahsinRupam
                Mar 13, 2017 at 15:23
                Don't reinvent the wheel once again, there is no point of using asynctask (it's crap), httpsurlconnection (as there are better alternatives like okhttp/volley), manual json parsing (what for if it can be done automatically with gson/jackson). Just use retrofit: vogella.com/tutorials/Retrofit/article.html
– Than
                Mar 13, 2017 at 15:23
                getting the error code networkonmainthreadexception 500. Nonsense. 500 means something different.
– greenapps
                Mar 13, 2017 at 15:32
            try {
                URL url = new URL(urlAdress);
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.setRequestMethod("POST");
                conn.setRequestProperty("Content-Type", "application/json;charset=UTF-8");
                conn.setRequestProperty("Accept","application/json");
                conn.setDoOutput(true);
                conn.setDoInput(true);
                JSONObject jsonParam = new JSONObject();
                jsonParam.put("timestamp", 1488873360);
                jsonParam.put("uname", message.getUser());
                jsonParam.put("message", message.getMessage());
                jsonParam.put("latitude", 0D);
                jsonParam.put("longitude", 0D);
                Log.i("JSON", jsonParam.toString());
                DataOutputStream os = new DataOutputStream(conn.getOutputStream());
                //os.writeBytes(URLEncoder.encode(jsonParam.toString(), "UTF-8"));
                os.writeBytes(jsonParam.toString());
                os.flush();
                os.close();
                Log.i("STATUS", String.valueOf(conn.getResponseCode()));
                Log.i("MSG" , conn.getResponseMessage());
                conn.disconnect();
            } catch (Exception e) {
                e.printStackTrace();
    thread.start();
Can you try with writing this in the createMsg() method: 
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
    try  {
        // The code written in doInBackground()
    } catch (Exception e) {
        e.printStackTrace();
thread.start(); 
The networkonmainthread exception comes when you run the network operations on the same thread. But, since you're using an async task, it should work fine. But, just to confirm.
        
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