如何从服务器获取回声

Question

I'm trying to get an echo reply from my server. The purpose of this is to check for internet connection and also to check the server status. If I get a reply, a dialog box will appear with a simple message. Same goes with not getting a reply.

The dialog box appeared when I get a reply, but it won't appear when I don't get a reply.

In my uploadDB.class, I have multiple cases that will perform different function in the PHP file. One of the case is a "ping" function and the other is an "updatecounter" function.

When I remove the "updatecounter" case in my uploadDB.class, everything seems to work. Due to my requirements, I'm not supposed to remove the "updatecounter" case.

Can someone advise me on how to solve this?

Below are my codes and error in Logcat.

PHP file

        if (isset($_POST['type'])){
        if ($_POST['type'] == "ping"){
        echo "success";
        }

MainActivity.class

public boolean isInternetConnected = false;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        pingTask();
    }

    private void pingTask() {
        new uploadDB(new uploadDB.returnResult() {
            @Override
            public void onFinish(String result) {
                if (result.equalsIgnoreCase("success")) {
                    isInternetConnected = true;
                    showdialog("Server Status", "Working");
                } else {
                    isInternetConnected = false;
                    showdialog("Server Status", "Not Working");
                }
            }
        }).execute("ping");
    }

uploadDB.class

protected String doInBackground(String... params) {
        String method = params[0];
        String data = "";
        String link = "www.example.com/example.php";

        switch (method){
            case "ping": {
                try{
                    data = URLEncoder.encode("type", "UTF-8") + "=" + URLEncoder.encode("ping", "UTF-8");
                    Log.e(TAG,"DATA: " + data);
                }catch (UnsupportedEncodingException e){
                    Log.e(TAG, "UnsupportedEncodingException: " + e.toString());
                }
                try {
                    URL url = new URL(link);
                    HttpURLConnection h = (HttpURLConnection) url.openConnection();
                    h.setDoInput(true);
                    h.setDoOutput(true);
                    OutputStreamWriter owriter =
                            new OutputStreamWriter(h.getOutputStream());
                    owriter.write(data);
                    owriter.flush();
                    BufferedReader b = new BufferedReader
                            (new InputStreamReader(h.getInputStream(), "UTF-8"), 8);
                    StringBuilder builder = new StringBuilder();
                    String line;
                    while ((line = b.readLine()) != null) {
                        builder.append(line);
                    }
                    return builder.toString();
                } catch (IOException e) {
                    Log.e(TAG, "IOException: " + e.toString());
                }
            }

          case "updatecounter": {
                String macAddress = params[1];
                String sensorname = params[2];
                String counter = params[3];
                try {
                    data = URLEncoder.encode("type", "UTF-8") + "=" + URLEncoder.encode("counter", "UTF-8")
                            + "&" + URLEncoder.encode("gate_name", "UTF-8") + "=" + URLEncoder.encode(sensorname, "UTF-8")
                            + "&" + URLEncoder.encode("mac", "UTF-8") + "=" + URLEncoder.encode(macAddress, "UTF-8")
                            + "&" + URLEncoder.encode("counter", "UTF-8") + "=" + URLEncoder.encode(counter, "UTF-8");
                    Log.e(TAG,"DATA: " + data);
                } catch (UnsupportedEncodingException e) {
                    Log.e(TAG, "UnsupportedEncodingException: " + e.toString());
                }

                try {
                    URL url = new URL(link);
                    HttpURLConnection h = (HttpURLConnection) url.openConnection();
                    h.setDoInput(true);
                    h.setDoOutput(true);
                    OutputStreamWriter owriter =
                            new OutputStreamWriter(h.getOutputStream());
                    owriter.write(data);
                    owriter.flush();
                    BufferedReader b = new BufferedReader
                            (new InputStreamReader(h.getInputStream(), "UTF-8"), 8);
                    StringBuilder builder = new StringBuilder();
                    String line;
                    while ((line = b.readLine()) != null) {
                        builder.append(line);
                    }
                    return builder.toString();
                } catch (IOException e) {
                    //activity.isInternetConnected = false;
                    Log.e(TAG, "IOException: " + e.toString());
                }
            }

Error in Logcat

Process: com.example.postserver, PID: 21624
    java.lang.RuntimeException: An error occurred while executing doInBackground()
        at android.os.AsyncTask$3.done(AsyncTask.java:353)
        at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
        at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
        at java.util.concurrent.FutureTask.run(FutureTask.java:271)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: java.lang.ArrayIndexOutOfBoundsException: length=1; index=1
        at com.example.postserver.uploadDB.doInBackground(uploadDB.java:69)
        at com.example.postserver.uploadDB.doInBackground(uploadDB.java:16)

Answer 1

you need to add a break at the end of the case. If you not add it, every case after that will be executed:

   switch (method){
        case "ping": {
            try{
                data = URLEncoder.encode("type", "UTF-8") + "=" + URLEncoder.encode("ping", "UTF-8");
                Log.e(TAG,"DATA: " + data);
            }catch (UnsupportedEncodingException e){
                Log.e(TAG, "UnsupportedEncodingException: " + e.toString());
            }
            try {
                URL url = new URL(link);
                HttpURLConnection h = (HttpURLConnection) url.openConnection();
                h.setDoInput(true);
                h.setDoOutput(true);
                OutputStreamWriter owriter =
                        new OutputStreamWriter(h.getOutputStream());
                owriter.write(data);
                owriter.flush();
                BufferedReader b = new BufferedReader
                        (new InputStreamReader(h.getInputStream(), "UTF-8"), 8);
                StringBuilder builder = new StringBuilder();
                String line;
                while ((line = b.readLine()) != null) {
                    builder.append(line);
                }
                return builder.toString();
            } catch (IOException e) {
                Log.e(TAG, "IOException: " + e.toString());
            }
        }
        break;
    case "updatecounter": {

Answer 2

You can get Any Response from server in android studio By

InputStream inputStream = httpURLConnection.getInputStream();
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream,"UTF-8");
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                String dataResponse = "";
                String inputLine = "";
                while((inputLine = bufferedReader.readLine()) != null){
                    dataResponse += inputLine;
                }
                bufferedReader.close();
                inputStream.close();
                httpURLConnection.disconnect();

After that You can Print out your Response

System.out.println(dataResponse);

Put That code After your Post Code