Android: How to check if the server is available?

问题

I am developing an application which connects to the server. By now the login and data transmission works fine if theserver is available. The problem arises when the server is unavailable. In this case the method sends a login request and waits for the response.

Does anyone know how to check if the server is available (visible)?

The pseudocode of the simple logic that has to be implemented is the following:

1. String serverAddress = (Read value from configuration file) //already done
2. boolean serverAvailable = (Check if the server serverAddress is available)//has to be implemented
3. (Here comes the logic which depends on serverAvailable)

回答1:

He probably needs Java code since he's working on Android. The Java equivalent -- which I believe works on Android -- should be:

InetAddress.getByName(host).isReachable(timeOut)

回答2:

With a simple ping-like test, this worked for me :

static public boolean isURLReachable(Context context) {
    ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo netInfo = cm.getActiveNetworkInfo();
    if (netInfo != null && netInfo.isConnected()) {
        try {
            URL url = new URL("http://192.168.1.13");   // Change to "http://google.com" for www  test.
            HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
            urlc.setConnectTimeout(10 * 1000);          // 10 s.
            urlc.connect();
            if (urlc.getResponseCode() == 200) {        // 200 = "OK" code (http connection is fine).
                Log.wtf("Connection", "Success !");
                return true;
            } else {
                return false;
            }
        } catch (MalformedURLException e1) {
            return false;
        } catch (IOException e) {
            return false;
        }
    }
    return false;
}

Do not forget to run this function in a thread (not in the main thread).

回答3:

you can use

InetAddress.getByName(host).isReachable(timeOut)

but it doesn't work fine when host is not answering on tcp 7. You can check if the host is available on that port what you need with help of this function:

public static boolean isHostReachable(String serverAddress, int serverTCPport, int timeoutMS){
    boolean connected = false;
    Socket socket;
    try {
        socket = new Socket();
        SocketAddress socketAddress = new InetSocketAddress(serverAddress, serverTCPport);
        socket.connect(socketAddress, timeoutMS);
        if (socket.isConnected()) {
            connected = true;
            socket.close();
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        socket = null;
    }
    return connected;
}

回答4:

public static boolean IsReachable(Context context) {
    // First, check we have any sort of connectivity
    final ConnectivityManager connMgr = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
    final NetworkInfo netInfo = connMgr.getActiveNetworkInfo();
    boolean isReachable = false;

    if (netInfo != null && netInfo.isConnected()) {
        // Some sort of connection is open, check if server is reachable
        try {
            URL url = new URL("http://www.google.com");
            //URL url = new URL("http://10.0.2.2");
            HttpURLConnection urlc = (HttpURLConnection) url.openConnection();
            urlc.setRequestProperty("User-Agent", "Android Application");
            urlc.setRequestProperty("Connection", "close");
            urlc.setConnectTimeout(10 * 1000);
            urlc.connect();
            isReachable = (urlc.getResponseCode() == 200);
        } catch (IOException e) {
            //Log.e(TAG, e.getMessage());
        }
    }

    return isReachable;
}

try it, work for me and dont forget actived android.permission.ACCESS_NETWORK_STATE

回答5:

Are you working with HTTP? You could then set a timeout on your HTTP connection, as such:

private void setupHttpClient() {
    BasicHttpParams httpParams = new BasicHttpParams();

    ConnManagerParams.setTimeout(httpParams, CONNECTION_TIMEOUT);
    //...

    ThreadSafeClientConnManager cm = new ThreadSafeClientConnManager(
            httpParams, schemeRegistry);
    this.httpClient = new DefaultHttpClient(cm, httpParams);
}

If you then execute a request, you will get an exception after the given timeout.

回答6:

public boolean isConnectedToServer(String url, int timeout) {
try{
    URL myUrl = new URL(url);
    URLConnection connection = myUrl.openConnection();
    connection.setConnectTimeout(timeout);
    connection.connect();
    return true;
} catch (Exception e) {
    // Handle your exceptions
    return false;
 }
}

回答7:

Oh, no no, the code in Java doesn't work: InetAddress.getByName("fr.yahoo.com").isReachable(200) although in the LogCat I saw its IP address (the same with 20000 ms of time out).

It seems that the use of the 'ping' command is convenient, for example:

Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec("ping fr.yahoo.com -c 1"); // other servers, for example
proc.waitFor();
int exit = proc.exitValue();
if (exit == 0) { // normal exit
    /* get output content of executing the ping command and parse it
     * to decide if the server is reachable
     */
} else { // abnormal exit, so decide that the server is not reachable
    ...
}

来源：https://stackoverflow.com/questions/1443166/android-how-to-check-if-the-server-is-available