How to ping an IP address

Question

I am using this part of code to ping an ip address in java but only pinging localhost is successful and for the other hosts the program says the host is unreachable. I disabled my firewall but still having this problem

public static void main(String[] args) throws UnknownHostException, IOException {
    String ipAddress = "127.0.0.1";
    InetAddress inet = InetAddress.getByName(ipAddress);

    System.out.println("Sending Ping Request to " + ipAddress);
    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");

    ipAddress = "173.194.32.38";
    inet = InetAddress.getByName(ipAddress);

    System.out.println("Sending Ping Request to " + ipAddress);
    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");
}

The output is:

Sending Ping Request to 127.0.0.1
Host is reachable
Sending Ping Request to 173.194.32.38
Host is NOT reachable

Kalimantan

Is it possible to ping that server if you're using ping directly? – Maccarone

What input are you entering into jTextField1? – Kirby

Yes !!! but in my program I can only ping localhost !!! – Kalimantan

I increased the timeout to 10 seconds but didn't work – Kalimantan

Check how your ipaddress is printing out, is it properly formatted for INetAddress.getByName();? – Kapoor

I'm entering the exact IP address , it is working for 127.0.0.1 but form example for 173.194.32.38 is not working , and says "the host is Unreachable " – Kalimantan

if the input was not correct , so that could not ping 127.0.0.1 !!! – Kalimantan

@user1529128 I have edited your question with a simple example that reproduces the behaviour you describe. Feel free to roll back the edit if you don't think it is what you are asking. – Hardman

@ assylias : thank you for your nice edit ! I'm new at stackoverflow and this was my firs question . thank you for helping me. – Kalimantan

@dystroy I tested with google ip address or any other valid ip , that's only working for 127.0.0.0/24 and 192.168.0.0/24 – Kalimantan

It seems you can't access the external network from your program (192.168 are on your LAN). As you can with other software, we can be pretty confident it's a local (meaning on your computer) firewall/router/dns problem. – Bazemore

possible duplicate of Why does InetAddress.isReachable return false, when I can ping the IP address? – Hardman

Ping Problem Is solved for me. Use this link. #21480468 – Zoan

Answer 1

You can not simply ping in Java as it relies on ICMP, which is sadly not supported in Java

http://mindprod.com/jgloss/ping.html

Use sockets instead

Hope it helps

Feder

I might now be out of context, but this is what worked for me, very well in fact: dnsjava.org Thanks everybody. – Smallman

There are better answers below – Overage

@AhmadArslan whatever answer you used to have posted at that link, it's gone now. So the link isn't really helpful anymore... you seem to have killed your own link... – Podite

Answer 2

InetAddress.isReachable() according to javadoc:

".. A typical implementation will use ICMP ECHO REQUESTs if the privilege can be obtained, otherwise it will try to establish a TCP connection on port 7 (Echo) of the destination host..".

Option #1 (ICMP) usually requires administrative (root) rights.

Adulation

Then why can you usually do it as a non-admin/non-root on most computers outside of Java? – Progesterone

To clarify: Do commands such as command-line ping not use ICMP packets? I was fairly certain they did. Is ping run in an administrative context? – Progesterone

Are you saying that the isReachable method ONLY uses TCP port 7 and it will NOT use ICMP ECHO REQUESTs? Or will it use ICMP if I somehow grant root privilege to my application? If the latter, then how do I allow my app to run as root? – Import

The ping command on Linux is set-uid root; that's why non-root users can utilize it, even though it uses ICMP ECHO_REQUEST. – Configurationism

This doesn't really work well: #9923043 – Backside

The spec is saying: "Best effort is made by the implementation to try to reach the host, but firewalls and server configuration may block requests resulting in a unreachable status while some specific ports may be accessible". In the case the port number is known, opening a connection to host:port is a better option. – Adulation

Answer 3

I think this code will help you:

public class PingExample {
    public static void main(String[] args){
        try{
            InetAddress address = InetAddress.getByName("192.168.1.103");
            boolean reachable = address.isReachable(10000);

            System.out.println("Is host reachable? " + reachable);
        } catch (Exception e){
            e.printStackTrace();
        }
    }
}

Grooved

Answer 4

Check your connectivity. On my Computer this prints REACHABLE for both IP's:

Sending Ping Request to 127.0.0.1
Host is reachable
Sending Ping Request to 173.194.32.38
Host is reachable

EDIT:

You could try modifying the code to use getByAddress() to obtain the address:

public static void main(String[] args) throws UnknownHostException, IOException {
    InetAddress inet;

    inet = InetAddress.getByAddress(new byte[] { 127, 0, 0, 1 });
    System.out.println("Sending Ping Request to " + inet);
    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");

    inet = InetAddress.getByAddress(new byte[] { (byte) 173, (byte) 194, 32, 38 });
    System.out.println("Sending Ping Request to " + inet);
    System.out.println(inet.isReachable(5000) ? "Host is reachable" : "Host is NOT reachable");
}

The getByName() methods may attempt some kind of reverse DNS lookup which may not be possible on your machine, getByAddress() might bypass that.

Dita

I'm sure I'm connected and I have even disabled my firewall and antivirus , but still it's not working ... – Kalimantan

It may still be your machine. What OS are you on? Have you tried the getByAddress() instead of getByName() method to ensure no reverse DNS lookup is attempted? – Dita

@ Durandal I'm using win7 and yes ! I tried getByAddress() instead of getByName() , There was no DNS lookup attempt , don't tell me there is no way for me please ! – Kalimantan

@Dita I can see the same behaviour as described by the OP and using getByAddress does not make a difference. I have posted a comment with a possible duplicate of the issue. – Hardman

@Durandal: why we need to type cast the ipaddress to byte in the second example , you have given ? – Shockheaded

@vamsi Because the IP is given as literals, and literals are considered to be of type int by the compiler. Because the value range of byte is -128 to 127, values outside that range require an explicit cast (e.g. literal 173). The "why" is rooted in javas byte being signed and IP addresses usually presented as unsigned bytes for readability. – Dita

Answer 5

You can use this method to ping hosts on Windows and other platforms:

private static boolean ping(String host) throws IOException, InterruptedException {
    boolean isWindows = System.getProperty("os.name").toLowerCase().contains("win");

    ProcessBuilder processBuilder = new ProcessBuilder("ping", isWindows? "-n" : "-c", "1", host);
    Process proc = processBuilder.start();

    int returnVal = proc.waitFor();
    return returnVal == 0;
}

Ardene

On windows you always get 1 as returnVal. No matter if it is reachable or not. – Fibrovascular

Had success with this both on Windows and Android – Yellowgreen

Worked fine on Windows 10 and Android 7.1.1 without root. – Quotation

Answer 6

short recommendation: don't use isReachable(), call the system ping, as proposed in some of the answers above.

long explanation:

• ping uses the ICMP network protcol. To use ICMP, a 'raw socket' is needed
• standard users are not allowed by the operating system to use raw sockets
• the following applies to a fedora 30 linux, windows systems should be similar
• if java runs as root, isReachable() actually sends ICMP ping requests
• if java does not run as root, isReachable() tries to connect to TCP port 7, known as the echo port. This service is commonly not used any more, trying to use it might yield improper results
• any kind of answer to the connection request, also a reject (TCP flag RST) yields a 'true' from isReachable()
• some firewalls send RST for any port that is not explicitly open. If this happens, you will get isReachable() == true for a host that does not even exist
• further tries to assign the necessary capabilities to a java process:
• setcap cap_net_raw+eip java executable (assign the right to use raw sockets)
• test: getcap java executable -> 'cap_net_raw+eip' (capability is assigned)
• the running java still sends a TCP request to port 7
• check of the running java process with getpcaps pid shows that the running java does not have the raw socket capablity. Obviously my setcap has been overridden by some security mechanism
• as security requirements are increasing, this is likely to become even more restricted, unless s.b. implements an exception especially for ping (but nothing found on the net so far)

Dimetric

The system ping isn't guaranteed to work either; some environments block all ICMP ECHO requests at their firewall. In particular, Azure (and hence Github Actions among other things) is one such environment. – Neusatz

Answer 7

It will work for sure

import java.io.*;
import java.util.*;

public class JavaPingExampleProgram
{

  public static void main(String args[]) 
  throws IOException
  {
    // create the ping command as a list of strings
    JavaPingExampleProgram ping = new JavaPingExampleProgram();
    List<String> commands = new ArrayList<String>();
    commands.add("ping");
    commands.add("-c");
    commands.add("5");
    commands.add("74.125.236.73");
    ping.doCommand(commands);
  }

  public void doCommand(List<String> command) 
  throws IOException
  {
    String s = null;

    ProcessBuilder pb = new ProcessBuilder(command);
    Process process = pb.start();

    BufferedReader stdInput = new BufferedReader(new InputStreamReader(process.getInputStream()));
    BufferedReader stdError = new BufferedReader(new InputStreamReader(process.getErrorStream()));

    // read the output from the command
    System.out.println("Here is the standard output of the command:\n");
    while ((s = stdInput.readLine()) != null)
    {
      System.out.println(s);
    }

    // read any errors from the attempted command
    System.out.println("Here is the standard error of the command (if any):\n");
    while ((s = stdError.readLine()) != null)
    {
      System.out.println(s);
    }
  }

}

Matney

If you change -c to -n, most likely. – Clio

@Supuhstar it will only work on OS that has ping command. Basically what it's doing above is fork a new process and make it run ping command from the OS. – Vachil

Answer 8

Just an addition to what others have given, even though they work well but in some cases if internet is slow or some unknown network problem exists, some of the codes won't work (isReachable()). But this code mentioned below creates a process which acts as a command line ping (cmd ping) to windows. It works for me in all cases, tried and tested.

Code :-

public class JavaPingApp {

public static void runSystemCommand(String command) {

    try {
        Process p = Runtime.getRuntime().exec(command);
        BufferedReader inputStream = new BufferedReader(
                new InputStreamReader(p.getInputStream()));

        String s = "";
        // reading output stream of the command
        while ((s = inputStream.readLine()) != null) {
            System.out.println(s);
        }

    } catch (Exception e) {
        e.printStackTrace();
    }
}

public static void main(String[] args) {

    String ip = "stackoverflow.com"; //Any IP Address on your network / Web
    runSystemCommand("ping " + ip);
}
}

Hope it helps, Cheers!!!

Insignificance

this could be vulnerable to command injection, always validate the input – Jocular

Answer 9

Even though this does not rely on ICMP on Windows, this implementation works pretty well with the new Duration API

public static Duration ping(String host) {
    Instant startTime = Instant.now();
    try {
        InetAddress address = InetAddress.getByName(host);
        if (address.isReachable(1000)) {
            return Duration.between(startTime, Instant.now());
        }
    } catch (IOException e) {
        // Host not available, nothing to do here
    }
    return Duration.ofDays(1);
}

Swint

Answer 10

On linux with oracle-jdk the code the OP submitted uses port 7 when not root and ICMP when root. It does do a real ICMP echo request when run as root as the documentation specifies.

If you running this on a MS machine you may have to run the app as administrator to get the ICMP behaviour.

Renascent

Answer 11

Here is a method for pinging an IP address in Java that should work on Windows and Unix systems:

import org.apache.commons.lang3.SystemUtils;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class CommandLine
{
    /**
     * @param ipAddress The internet protocol address to ping
     * @return True if the address is responsive, false otherwise
     */
    public static boolean isReachable(String ipAddress) throws IOException
    {
        List<String> command = buildCommand(ipAddress);
        ProcessBuilder processBuilder = new ProcessBuilder(command);
        Process process = processBuilder.start();

        try (BufferedReader standardOutput = new BufferedReader(new InputStreamReader(process.getInputStream())))
        {
            String outputLine;

            while ((outputLine = standardOutput.readLine()) != null)
            {
                // Picks up Windows and Unix unreachable hosts
                if (outputLine.toLowerCase().contains("destination host unreachable"))
                {
                    return false;
                }
            }
        }

        return true;
    }

    private static List<String> buildCommand(String ipAddress)
    {
        List<String> command = new ArrayList<>();
        command.add("ping");

        if (SystemUtils.IS_OS_WINDOWS)
        {
            command.add("-n");
        } else if (SystemUtils.IS_OS_UNIX)
        {
            command.add("-c");
        } else
        {
            throw new UnsupportedOperationException("Unsupported operating system");
        }

        command.add("1");
        command.add(ipAddress);

        return command;
    }
}

Make sure to add Apache Commons Lang to your dependencies.

Ramillies

this example may not work on non-english operating systems. On windows, there's also the "general failure" error message and there may be others – Jocular

Answer 12

I prefer to this way:

   /**
     *
     * @param host
     * @return true means ping success,false means ping fail.
     * @throws IOException
     * @throws InterruptedException
     */
    private static boolean ping(String host) throws IOException, InterruptedException {
        boolean isWindows = System.getProperty("os.name").toLowerCase().contains("win");

        ProcessBuilder processBuilder = new ProcessBuilder("ping", isWindows? "-n" : "-c", "1", host);
        Process proc = processBuilder.start();
        return proc.waitFor(200, TimeUnit.MILLISECONDS);
    }

This way can limit the blocking time to the specific time,such as 200 ms.

It works well in MacOS、Android and Windows, and should used in JDK 1.8.

This idea comes from Mohammad Banisaeid,but I can't comment. (You must have 50 reputation to comment)

Wiltshire

Answer 13

I know this has been answered with previous entries, but for anyone else that comes to this question, I did find a way that did not require having use the "ping" process in windows and then scrubbing the output.

What I did was use JNA to invoke Window's IP helper library to do an ICMP echo

See my own answer to my own similar issue

Ophiology

Answer 14

InetAddress is not always return correct value. It is successful in case of Local Host but for other hosts this shows that the host is unreachable. Try using ping command as given below.

try {
    String cmd = "cmd /C ping -n 1 " + ip + " | find \"TTL\"";        
    Process myProcess = Runtime.getRuntime().exec(cmd);
    myProcess.waitFor();

    if(myProcess.exitValue() == 0) {

    return true;
    }
    else {
        return false;
    }
}
catch (Exception e) {
    e.printStackTrace();
    return false;
}

Phiona

Answer 15

I tried a couple of options:

1. Java InetAddress

InetAddress.getByName(ipAddress), the network on windows started misbehaving after trying a couple of times

2. Java HttpURLConnection

           URL siteURL = new URL(url);
           connection = (HttpURLConnection) siteURL.openConnection();
           connection.setRequestMethod("GET");
           connection.setConnectTimeout(pingTime);
           connection.connect();
   
           code = connection.getResponseCode();
           if (code == 200) {
               code = 200;
           }.
   

This was reliable but a bit slow

3. Windows Batch File

I finally settled to creating a batch file on my windows machine with the following contents: ping.exe -n %echoCount% %pingIp% Then I called the .bat file in my java code using

public int pingBat(Network network) {
ProcessBuilder pb = new ProcessBuilder(pingBatLocation);
Map<String, String> env = pb.environment();

env.put(
        "echoCount", noOfPings + "");
env.put(
        "pingIp", pingIp);
File outputFile = new File(outputFileLocation);
File errorFile = new File(errorFileLocation);

pb.redirectOutput(outputFile);

pb.redirectError(errorFile);

Process process;

try {
    process = pb.start();
    process.waitFor();
    String finalOutput = printFile(outputFile);
    if (finalOutput != null && finalOutput.toLowerCase().contains("reply from")) {
        return 200;
    } else {
        return 202;
    }
} catch (IOException e) {
    log.debug(e.getMessage());
    return 203;
} catch (InterruptedException e) {
    log.debug(e.getMessage());
    return 204;
}

}

This proved to be the fastest and most reliable way

Phelips

The batch example isn't right. The output can easily be "reply from x.y.z.a: Destination host unreachable" which would return a positive answer. – Jocular

Answer 16

You can use java in a shell script, without compiling it (java does this on the fly) and run a "ping" type test for any host/port. This takes 2 arguments, the host and the port. Basic idea comes from this answer

e.g.

# test if host and port can be opened from java
$ test_host_and_port myhost 443

test_host_and_port

#!/usr/bin/java --source 11
import java.net.InetAddress;
import java.net.Socket;

public class PingExample {
  public static void main(String[] args){
    try{
      boolean result = serverListening(args[0], Integer.valueOf(args[1]));

      System.out.println("Is host reachable? " + args[0] + ", " + result);
    } catch (Exception e){
      e.printStackTrace();
    }
  }
  
  public static boolean serverListening(String host, int port)
  {
    Socket s = null;
    try
    {
      s = new Socket(host, port);
      return true;
    }
    catch (Exception e)
    {
      return false;
    }
    finally
    {
      if(s != null)
        try {s.close();}
      catch(Exception e){}
    }
  }
}

Tondatone

Answer 17

This should work:

import java.io.BufferedReader;
import java.io.InputStreamReader;

public class Pinger {

private static String keyWordTolookFor = "average";

public Pinger() {
    // TODO Auto-generated constructor stub
}


 public static void main(String[] args) {
 //Test the ping method on Windows.
 System.out.println(ping("192.168.0.1")); }


public String ping(String IP) {
    try {
        String line;
        Process p = Runtime.getRuntime().exec("ping -n 1 " + IP);
        BufferedReader input = new BufferedReader(new InputStreamReader(p.getInputStream()));
        while (((line = input.readLine()) != null)) {

            if (line.toLowerCase().indexOf(keyWordTolookFor.toLowerCase()) != -1) {

                String delims = "[ ]+";
                String[] tokens = line.split(delims);
                return tokens[tokens.length - 1];
            } 
        }

        input.close();
    } catch (Exception err) {
        err.printStackTrace();
    }
    return "Offline";
}

}

Putdown

Please add a description of how your code works. It will help OP in understanding your code when he applies it. – Delft

Had this to review in the "low quality queue"... But since it dates from an hour... Maybe it will be improved with explanations soon. What is the hurry to post an answer to a 2012 question? Well... I just skip it for now. – Skirting

Thank you for all of your comments. First of all this is a class and method to work with windows ONLY. I needed to as a ping time to a project so I came up with this which is dirty but quick if you are working on windows. This is a super quick ~5 min developed code for pinging an IPv4 host as you can see from the code itself. This class and it's method gets a String as an IP address and returns the average time for the ping that is generated in windows CMD. CMD those the ping and this code reads the output to reach to the line that some numerical stats are given. – Putdown

It "tokenizes" the output when min, max and average are given and returns the average time. It is a bit crazy that you can have an average time out of only one ping but this is windows and it does it anyways. – Putdown

Please try it out for yourself on Windows before marking it down. It is an easy / dirty fix for a big problem. – Putdown

Louys Patrice Bessette, Thank you for your comment. my code is here to get voted by pros like you. This is my first ever posting. I like my own method over what I see here. Best. – Putdown

the ping() method should be static. (that's just at first sight, without running it) – Legofmutton