blocks|key|1236236|text|创建一个指向某个站点(如www.whatismyip.com+)的HttpURLConnection并解析它:-)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1236237|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Make a HttpURLConnection to some site like www.whatismyip.com and parse that :-)

blocks|key|1021655|text|这并不容易，因为LAN内的机器通常不关心其路由器到internet的外部IP。它根本不需要它！|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1021656|我建议您通过打开像http://www.whatismyip.com/这样的站点并通过解析html结果来获得IP号来利用这一点。应该不会那么难吧！|offset|length|1021657|entityMap|0|LINK|mutability|MUTABLE|url|http://www.whatismyip.com/^0|0|9|Q|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

It's not that easy since a machine inside a LAN usually doesn't care about the external IP of its router to the internet.. it simply doesn't need it!

I would suggest you to exploit this by opening a site like <a href="http://www.whatismyip.com/" rel="nofollow noreferrer">http://www.whatismyip.com/</a> and getting the IP number by parsing the html results.. it shouldn't be that hard!

blocks|key|1236328|text|事实是:从你提出问题的意义上说，“你不能”。NAT发生在协议之外。您的机器内核无法知道您的NAT盒是如何从外部IP地址映射到内部IP地址的。这里的其他答案提供了一些技巧，包括与外部网站交谈的方法。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1236329|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

The truth is: 'you can't' in the sense that you posed the question. NAT happens outside of the protocol. There is no way for your machine's kernel to know how your NAT box is mapping from external to internal IP addresses. Other answers here offer tricks involving methods of talking to outside web sites.

blocks|key|1021717|text|http://jstun.javawi.de/会做到这一点-前提是你的网关设备确实会昏迷)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1021718|entityMap|0|LINK|mutability|MUTABLE|url|http://jstun.javawi.de/^0|0|N|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

<a href="http://jstun.javawi.de/" rel="nofollow">http://jstun.javawi.de/</a> will do it - provided your gateway device does STUN )most do)

blocks|key|1021747|text|正如@Donal+Fellows所写的，你必须查询网络接口而不是机器。javadocs中的这段代码对我很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1021748|以下示例程序列出了计算机上的所有网络接口及其地址：|1021749|import+java.io.*;
import+java.net.*;
import+java.util.*;
import+static+java.lang.System.out;

public+class+ListNets+{

++++public+static+void+main(String+args[])+throws+SocketException+{
++++++++Enumeration<NetworkInterface>+nets+=+NetworkInterface.getNetworkInterfaces();
++++++++for+(NetworkInterface+netint+:+Collections.list(nets))
++++++++++++displayInterfaceInformation(netint);
++++}

++++static+void+displayInterfaceInformation(NetworkInterface+netint)+throws+SocketException+{
++++++++out.printf("Display+name:+%25s\n",+netint.getDisplayName());
++++++++out.printf("Name:+%25s\n",+netint.getName());
++++++++Enumeration<InetAddress>+inetAddresses+=+netint.getInetAddresses();
++++++++for+(InetAddress+inetAddress+:+Collections.list(inetAddresses))+{
++++++++++++out.printf("InetAddress:+%25s\n",+inetAddress);
++++++++}
++++++++out.printf("\n");
+++++}
}+|code-block|syntax|javascript|1021750|以下是示例程序的示例输出：|1021751|Display+name:+TCP+Loopback+interface
Name:+lo
InetAddress:+/127.0.0.1

Display+name:+Wireless+Network+Connection
Name:+eth0
InetAddress:+/192.0.2.0|1021752|来自docs.oracle.com|offset|length|1021753|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/tutorial/networking/nifs/listing.html^0|0|0|0|0|0|2|F|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Z|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|10|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|11|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|13|8|@]|9|@$O|14|P|15|1|16]]|A|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|R|$S|$5|T|U|V|A|$W|X]]]]

As @Donal Fellows wrote, you have to query the network interface instead of the machine. This code from the javadocs worked for me:

The following example program lists all the network interfaces and their addresses on a machine:

<pre><code>import java.io.*;
import java.net.*;
import java.util.*;
import static java.lang.System.out;

public class ListNets {

 public static void main(String args[]) throws SocketException {
 Enumeration&lt;NetworkInterface&gt; nets = NetworkInterface.getNetworkInterfaces();
 for (NetworkInterface netint : Collections.list(nets))
 displayInterfaceInformation(netint);
 }

 static void displayInterfaceInformation(NetworkInterface netint) throws SocketException {
 out.printf("Display name: %s\n", netint.getDisplayName());
 out.printf("Name: %s\n", netint.getName());
 Enumeration&lt;InetAddress&gt; inetAddresses = netint.getInetAddresses();
 for (InetAddress inetAddress : Collections.list(inetAddresses)) {
 out.printf("InetAddress: %s\n", inetAddress);
 }
 out.printf("\n");
 }
} 
</code></pre>

The following is sample output from the example program:

<pre><code>Display name: TCP Loopback interface
Name: lo
InetAddress: /127.0.0.1

Display name: Wireless Network Connection
Name: eth0
InetAddress: /192.0.2.0
</code></pre>

From <a href="http://docs.oracle.com/javase/tutorial/networking/nifs/listing.html" rel="noreferrer">docs.oracle.com</a>

blocks|key|1236469|text|@stivlo的其中一条评论值得一提：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1236470|您可以使用亚马逊服务http://checkip.amazonaws.com|offset|length|1236471|import+java.io.BufferedReader;
import+java.io.IOException;
import+java.io.InputStreamReader;
import+java.net.URL;

public+class+IpChecker+{

++++public+static+String+getIp()+throws+Exception+{
++++++++URL+whatismyip+=+new+URL("http://checkip.amazonaws.com");
++++++++BufferedReader+in+=+null;
++++++++try+{
++++++++++++in+=+new+BufferedReader(new+InputStreamReader(
++++++++++++++++++++whatismyip.openStream()));
++++++++++++String+ip+=+in.readLine();
++++++++++++return+ip;
++++++++}+finally+{
++++++++++++if+(in+!=+null)+{
++++++++++++++++try+{
++++++++++++++++++++in.close();
++++++++++++++++}+catch+(IOException+e)+{
++++++++++++++++++++e.printStackTrace();
++++++++++++++++}
++++++++++++}
++++++++}
++++}
}|code-block|syntax|javascript|1236472|entityMap|0|LINK|mutability|MUTABLE|url|http://checkip.amazonaws.com/^0|0|A|S|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@$D|U|E|V|1|W]]|A|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

One of the comments by @stivlo deserves to be an answer:

You can use the Amazon service <a href="http://checkip.amazonaws.com">http://checkip.amazonaws.com</a>

<pre><code>import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;

public class IpChecker {

 public static String getIp() throws Exception {
 URL whatismyip = new URL("http://checkip.amazonaws.com");
 BufferedReader in = null;
 try {
 in = new BufferedReader(new InputStreamReader(
 whatismyip.openStream()));
 String ip = in.readLine();
 return ip;
 } finally {
 if (in != null) {
 try {
 in.close();
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 }
 }
}
</code></pre>

blocks|key|1236495|text|System.out.println(pageCrawling.getHtmlFromURL("http://ipecho.net/plain"));|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1236496|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>System.out.println(pageCrawling.getHtmlFromURL("http://ipecho.net/plain"));
</code></pre>

blocks|key|1021848|text|这个怎么样？它很简单，对我来说效果最好:)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1021849|import+java.io.BufferedReader;
import+java.io.IOException;
import+java.io.InputStreamReader;
import+java.net.MalformedURLException;
import+java.net.URL;


public+class+IP+{
++++public+static+void+main(String+args[])+{
++++++++new+IP();
++++}

++++public+IP()+{
++++++++URL+ipAdress;

++++++++try+{
++++++++++++ipAdress+=+new+URL("http://myexternalip.com/raw");

++++++++++++BufferedReader+in+=+new+BufferedReader(new+InputStreamReader(ipAdress.openStream()));

++++++++++++String+ip+=+in.readLine();
++++++++++++System.out.println(ip);
++++++++}+catch+(MalformedURLException+e)+{
++++++++++++e.printStackTrace();
++++++++}+catch+(IOException+e)+{
++++++++++++e.printStackTrace();
++++++++}
++++}
}|code-block|syntax|javascript|1021850|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

How about this? It's simple and worked the best for me :)

<pre><code>import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;


public class IP {
 public static void main(String args[]) {
 new IP();
 }

 public IP() {
 URL ipAdress;

 try {
 ipAdress = new URL("http://myexternalip.com/raw");

 BufferedReader in = new BufferedReader(new InputStreamReader(ipAdress.openStream()));

 String ip = in.readLine();
 System.out.println(ip);
 } catch (MalformedURLException e) {
 e.printStackTrace();
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
}
</code></pre>

blocks|key|1236606|text|另一种解决方案是执行外部命令，显然，这种解决方案限制了应用程序的可移植性。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1236607|例如，对于在Windows上运行的应用程序，可以通过jPowershell执行PowerShell命令，如以下代码所示：|1236608|public+String+getMyPublicIp()+{
++++//+PowerShell+command
++++String+command+=+"(Invoke-WebRequest+ifconfig.me/ip).Content.Trim()";
++++String+powerShellOut+=+PowerShell.executeSingleCommand(command).getCommandOutput();

++++//+Connection+failed
++++if+(powerShellOut.contains("InvalidOperation"))+{
++++++++powerShellOut+=+null;
++++}
++++return+powerShellOut;
}|code-block|syntax|javascript|1236609|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

An alternative solution is to execute an external command, obviously, this solution limits the portability of the application.


For example, for an application that runs on Windows, a PowerShell command can be executed through jPowershell, as shown in the following code:

<pre><code>public String getMyPublicIp() {
 // PowerShell command
 String command = &quot;(Invoke-WebRequest ifconfig.me/ip).Content.Trim()&quot;;
 String powerShellOut = PowerShell.executeSingleCommand(command).getCommandOutput();

 // Connection failed
 if (powerShellOut.contains(&quot;InvalidOperation&quot;)) {
 powerShellOut = null;
 }
 return powerShellOut;
}
</code></pre>

I'm not too sure how to go about getting the external IP address of the machine as a computer outside of a network would see it.

My following IPAddress class only gets the local IP address of the machine.

<pre><code>public class IPAddress {

 private InetAddress thisIp;

 private String thisIpAddress;

 private void setIpAdd() {
 try {
 InetAddress thisIp = InetAddress.getLocalHost();
 thisIpAddress = thisIp.getHostAddress().toString();
 } catch (Exception e) {
 }
 }

 protected String getIpAddress() {
 setIpAdd();
 return thisIpAddress;
 }
}
</code></pre>

Getting the 'external' IP address in Java

路由器

Windows

路由

我不太确定如何获取机器的外部IP地址，因为网络之外的计算机会看到它。下面的IPAddress类只获取机器的本地IP地址。public class IPAddress {    private InetAddress thisIp;    private String thisIpAddress;    private ...

问在Java中获取‘外部’IP地址
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