无法连接到服务器

Question

我试图通过android studio上的Android应用程序连接到服务器，但我使用下面的代码遇到了一些麻烦：

链接是：

static final String SERVICE_API_URL = "http://192.168.90.74/android/user.php";


public class AccessServiceAPI {

    /**
     * Call service api with GET method and then return result form service as json string
     * @param url
     * @return
     */
    public String getJSONStringFromUrl_GET(String url) {
        JSONArray jsonArray = null;
        HttpURLConnection httpURLConnection = null;
        BufferedReader bufferedReader;
        StringBuilder stringBuilder;
        String line;
        String jsonString = "";
        try {
            URL u = new URL(url);
            httpURLConnection = (HttpURLConnection) u.openConnection();
            httpURLConnection.setRequestMethod("GET");
            bufferedReader = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream()));
            stringBuilder = new StringBuilder();

            while ((line = bufferedReader.readLine()) != null) {
                stringBuilder.append(line + '\n');
            }
            jsonString = stringBuilder.toString();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            httpURLConnection.disconnect();
        }

        return jsonString;
    }




    /**
     * Convert json string to json object
     * @param jsonString
     * @return
     */
    public JSONObject convertJSONString2Obj(String jsonString) {
        JSONObject jObj = null;
        try {
            Log.w("convertJSONString2Obj", "JsonString=" + jsonString);
            jObj = new JSONObject(jsonString);
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return jObj;
    }

    /**
     * Get json string from URL with method POST
     * @param serviceUrl
     * @param params post data
     * @return json string
     */
    public String getJSONStringWithParam_POST(String serviceUrl, Map<String, String> params)
            throws IOException
    {
        JSONArray jsonArray = null;
        String jsonString = null;
        HttpURLConnection conn = null;
        String line;

        URL url;
        try
        {
            url = new URL(serviceUrl);
        }
        catch (MalformedURLException e)
        {
            throw new IllegalArgumentException("invalid url: " + serviceUrl);
        }

        StringBuilder bodyBuilder = new StringBuilder();
        Iterator<Map.Entry<String, String>> iterator = params.entrySet().iterator();
        // constructs the POST body using the parameters
        while (iterator.hasNext())
        {
            Map.Entry<String, String> param = iterator.next();
            bodyBuilder.append(param.getKey()).append('=')
                    .append(param.getValue());
            if (iterator.hasNext()) {
                bodyBuilder.append('&');
            }
        }

        String body = bodyBuilder.toString();
        Log.w("getJSONStringWithParam", "param=>" + body);
        byte[] bytes = body.getBytes();
        try {

            conn = (HttpURLConnection) url.openConnection();
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setFixedLengthStreamingMode(bytes.length);
            conn.setRequestMethod("POST");
            conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");
            // post the request
            OutputStream out = conn.getOutputStream();
            out.write(bytes);
            out.close();
            // handle the response
            int status = conn.getResponseCode();

            Log.w("getJSONStringWithParam", "Response Status = " + status);
            if (status != 200) {
                throw new IOException("Post failed with error code " + status);
            }

            BufferedReader  bufferedReader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            StringBuilder stringBuilder = new StringBuilder();


            while ((line = bufferedReader.readLine()) != null)
            {
                stringBuilder.append(line + '\n');
            }

            jsonString = stringBuilder.toString();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            conn.disconnect();
        }

        return jsonString;
    }


    public String getJSONStringWithParam_POST(String serviceUrl,String params)
            throws IOException
    {
        JSONArray jsonArray = null;
        String jsonString = null;
        HttpURLConnection conn = null;
        String line;

        URL url;
        try
        {
            url = new URL(serviceUrl);
        }
        catch (MalformedURLException e)
        {
            throw new IllegalArgumentException("invalid url: " + serviceUrl);
        }

        Log.w("getJSONStringWithParam", "param=>" + params);
        byte[] bytes = params.getBytes();
        try {

            conn = (HttpURLConnection) url.openConnection();
            conn.setDoOutput(true);
            conn.setUseCaches(false);
            conn.setFixedLengthStreamingMode(bytes.length);
            conn.setRequestMethod("POST");
            //conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded;charset=UTF-8");
            conn.setRequestProperty("Content-Type", "application/json");
            conn.connect();
            // post the request
            OutputStream out = conn.getOutputStream();
            out.write (bytes);
            out.close();
            // handle the response
            int status = conn.getResponseCode();

            Log.w("getJSONStringWithParam", "Response Status = " + status);
            if (status != 200) {
                throw new IOException("Post failed with error code " + status);
            }

            BufferedReader  bufferedReader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            StringBuilder stringBuilder = new StringBuilder();


            while ((line = bufferedReader.readLine()) != null)
            {
                stringBuilder.append(line + '\n');
            }

            jsonString = stringBuilder.toString();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (ProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            conn.disconnect();
        }

        return jsonString;
    }
}

，错误如下：

W/getJSONStringWithParam: param=>username=u&password=0000&action=login
I/System: core_booster, getBoosterConfig = false
W/System.err: java.net.ConnectException: failed to connect to /192.168.90.74 (port 80): connect failed: ENETUNREACH (Network is unreachable)

注意：我想提一下这个相同的代码以前工作过，一旦我重新启动我的电脑，它再也没有用了！

先谢谢你了！