blocks|key|1487871|text|SE6中的java.net.InterfaceAddress有一个getNetworkPrefixLength方法，顾名思义，它返回网络前缀长度。如果您希望子网掩码采用该格式，则可以从中计算子网掩码。java.net.InterfaceAddress同时支持IPv4和IPv6。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1487872|多个网络应用程序API中的getSubnetMask()返回指定IP地址(一个本地系统可能有多个本地IP地址)的java.net.InetAddress形式的子网掩码|1487873|entityMap|0|LINK|mutability|MUTABLE|url|http://java.sun.com/javase/6/docs/api/java/net/InterfaceAddress.html#getNetworkPrefixLength()^0|2S|P|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

java.net.InterfaceAddress in SE6 has a getNetworkPrefixLength method that returns, as the name suggests, the network prefix length. You can calculate the subnet mask from this if you would rather have it in that format. <a href="http://java.sun.com/javase/6/docs/api/java/net/InterfaceAddress.html#getNetworkPrefixLength()" rel="nofollow noreferrer">java.net.InterfaceAddress</a> supports both IPv4 and IPv6.

getSubnetMask() in several network application APIs returns subnet mask in java.net.InetAddress form for specified IP address (a local system may have many local IP addresses)

blocks|key|1273259|text|localhost接口的第一个地址的网络掩码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1273260|InetAddress+localHost+=+Inet4Address.getLocalHost();
NetworkInterface+networkInterface+=+NetworkInterface.getByInetAddress(localHost);
networkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength();|code-block|syntax|javascript|1273261|一种更完整的方法：|1273262|InetAddress+localHost+=+Inet4Address.getLocalHost();
NetworkInterface+networkInterface+=+NetworkInterface.getByInetAddress(localHost);

for+(InterfaceAddress+address+:+networkInterface.getInterfaceAddresses())+{
++++System.out.println(address.getNetworkPrefixLength());
}|1273263|/24表示255.255.255。|1273264|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

the netmask of the first address of the localhost interface:

<pre><code>InetAddress localHost = Inet4Address.getLocalHost();
NetworkInterface networkInterface = NetworkInterface.getByInetAddress(localHost);
networkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength();
</code></pre>

a more complete approach:

<pre><code>InetAddress localHost = Inet4Address.getLocalHost();
NetworkInterface networkInterface = NetworkInterface.getByInetAddress(localHost);

for (InterfaceAddress address : networkInterface.getInterfaceAddresses()) {
 System.out.println(address.getNetworkPrefixLength());
}
</code></pre>

/24 means 255.255.255.

blocks|key|1273356|text|顺便说一句，在过去我曾尝试使用InterfaceAddress.getNetworkPrefixLength()和InterfaceAddress.getBroadcast()，但它们不能返回准确的信息(这是在Windows上，使用SunJDK1.6.0更新10)。网络前缀长度是128+(不是24，它在我的网络上)，返回的广播地址是255.255.255.255+(不是192.168.1.255，它在我的网络上)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1273357|詹姆斯|1273358|更新:我刚刚找到了这里发布的解决方案：|1273359|+++++http://forums.sun.com/thread.jspa?threadID=5277744|code-block|syntax|javascript|1273360|您需要阻止Java使用IPv6，这样它就不会通过IPv6访问IPv4。在命令行中添加-Djava.net.preferIPv4Stack=true可以修复来自InterfaceAddress.getNetworkPrefixLength()和InterfaceAddress.getBroadcast()的结果。|1273361|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|R|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

FWIW, in the past I'd tried using InterfaceAddress.getNetworkPrefixLength() and InterfaceAddress.getBroadcast(), but they don't return accurate info (this is on Windows, with Sun JDK 1.6.0 update 10). The network prefix length is 128 (not 24, which it is on my network), and the broadcast address returned is 255.255.255.255 (not 192.168.1.255, which it is on my network).

James

Update: I just found the solution posted here:

<pre><code> http://forums.sun.com/thread.jspa?threadID=5277744
</code></pre>

You need to prevent Java from using IPv6, so that it isn't getting to IPv4 via IPv6.
Adding -Djava.net.preferIPv4Stack=true to the command line fixes the results from InterfaceAddress.getNetworkPrefixLength() and InterfaceAddress.getBroadcast() for me.

blocks|key|1488033|text|我设计了一个非常简单的IPv4+only解决方案。我需要它来为这里的子网生成网络掩码，以便正确地委派这些子网。我知道我可以生成32个可能的掩码的表，但我更喜欢每次都计算它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1488034|所以这是我的解决方案。|1488035|/*
+*+Get+network+mask+for+the+IP+address+and+network+prefix+specified...
+*+The+network+mask+will+be+returned+has+an+IP,+thus+you+can
+*+print+it+out+with+.getHostAddress()...
+*/
public+static+InetAddress+getIPv4LocalNetMask(InetAddress+ip,+int+netPrefix)+{

++++try+{
++++++++//+Since+this+is+for+IPv4,+it's+32+bits,+so+set+the+sign+value+of
++++++++//+the+int+to+"negative"...
++++++++int+shiftby+=+(1<<31);
++++++++//+For+the+number+of+bits+of+the+prefix+-1+(we+already+set+the+sign+bit)
++++++++for+(int+i=netPrefix-1;+i>0;+i--)+{
++++++++++++//+Shift+the+sign+right...+Java+makes+the+sign+bit+sticky+on+a+shift...
++++++++++++//+So+no+need+to+"set+it+back+up"...
++++++++++++shiftby+=+(shiftby+>>+1);
++++++++}
++++++++//+Transform+the+resulting+value+in+xxx.xxx.xxx.xxx+format,+like+if
++++++++///+it+was+a+standard+address...
++++++++String+maskString+=+Integer.toString((shiftby+>>+24)+&+255)+%2B+"."+%2B+Integer.toString((shiftby+>>+16)+&+255)+%2B+"."+%2B+Integer.toString((shiftby+>>+8)+&+255)+%2B+"."+%2B+Integer.toString(shiftby+&+255);
++++++++//+Return+the+address+thus+created...
++++++++return+InetAddress.getByName(maskString);
++++}
++++++++catch(Exception+e){e.printStackTrace();
++++}
++++//+Something+went+wrong+here...
++++return+null;
}|code-block|syntax|javascript|1488036|您只需使用要使用的IP和前缀调用它，它将为您生成网络掩码。|1488037|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

I devised an IPv4 only solution that is simple enough. I needed that to generate netmask for subnetworks here in order to delegate those subnets correctly. I know I could have generated a table of the 32 possible masks, but I prefered to get it computed each time.

So here is my solution.

<pre><code>/*
 * Get network mask for the IP address and network prefix specified...
 * The network mask will be returned has an IP, thus you can
 * print it out with .getHostAddress()...
 */
public static InetAddress getIPv4LocalNetMask(InetAddress ip, int netPrefix) {

 try {
 // Since this is for IPv4, it's 32 bits, so set the sign value of
 // the int to "negative"...
 int shiftby = (1&lt;&lt;31);
 // For the number of bits of the prefix -1 (we already set the sign bit)
 for (int i=netPrefix-1; i&gt;0; i--) {
 // Shift the sign right... Java makes the sign bit sticky on a shift...
 // So no need to "set it back up"...
 shiftby = (shiftby &gt;&gt; 1);
 }
 // Transform the resulting value in xxx.xxx.xxx.xxx format, like if
 /// it was a standard address...
 String maskString = Integer.toString((shiftby &gt;&gt; 24) &amp; 255) + "." + Integer.toString((shiftby &gt;&gt; 16) &amp; 255) + "." + Integer.toString((shiftby &gt;&gt; 8) &amp; 255) + "." + Integer.toString(shiftby &amp; 255);
 // Return the address thus created...
 return InetAddress.getByName(maskString);
 }
 catch(Exception e){e.printStackTrace();
 }
 // Something went wrong here...
 return null;
}
</code></pre>

You just call it with the IP and the prefix you want to use, it will generate the netmask for you.

blocks|key|1488080|text|我刚刚完成了用Java划分网络子网的API的开发工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1488081|https://launchpad.net/subnettingapi|offset|length|1488082|它有这样的功能，甚至更多。|1488083|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|Z|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@$D|Q|E|R|1|S]]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@]|A|$]]|$1|H|3|-4|5|6|7|U|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|C]]]]

I just finished working on an API for subnetting networks with Java.

<a href="https://launchpad.net/subnettingapi" rel="nofollow">https://launchpad.net/subnettingapi</a>

it has that functionality and more.

blocks|key|1488140|text|我发现：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1488141|NetworkInterface+networkInterface+=+NetworkInterface.getByInetAddress(localHost);|code-block|syntax|javascript|1488142|要获得ipv6的子网掩码，我们可以使用：|1488143|+networkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength();+|1488144|要获得ipv4的子网掩码，我们可以使用：|1488145|networkInterface.getInterfaceAddresses().get(1).getNetworkPrefixLength();|1488146|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

I found that:

<pre><code>NetworkInterface networkInterface = NetworkInterface.getByInetAddress(localHost);
</code></pre>

To get subnetmask for ipv6 we can use:

<pre><code> networkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength(); 
</code></pre>

To get subnetmask for ipv4 we can use:

<pre><code>networkInterface.getInterfaceAddresses().get(1).getNetworkPrefixLength();
</code></pre>

blocks|key|1488200|text|这是一个答案，如何从WIFI连接获得一个子掩码：link|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1488201|我根据自己的需要对其进行了修改，如下所示：|1488202|private+static+String+intToIP(int+ipAddress)+{
++++String+ret+=+String.format("%25d.%25d.%25d.%25d",+(ipAddress+&+0xff),
++++++++++++(ipAddress+>>+8+&+0xff),+(ipAddress+>>+16+&+0xff),
++++++++++++(ipAddress+>>+24+&+0xff));

++++return+ret;
}

public+static+String+GetSubnetMask_WIFI()+{

++++WifiManager+wifiManager+=+(WifiManager)+Global.getMainActivity()
++++++++++++.getSystemService(Context.WIFI_SERVICE);
++++WifiInfo+wifiInfo+=+wifiManager.getConnectionInfo();

++++DhcpInfo+dhcp+=+wifiManager.getDhcpInfo();
++++String+mask+=+intToIP(dhcp.netmask);

++++return+mask;
}|code-block|syntax|javascript|1488203|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/5387036/how-to-get-gateway-and-subnet-mask-details-in-android-programmatically^0|O|4|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

Here is an answer, how to get a submask from WIFI connection: <a href="https://stackoverflow.com/questions/5387036/how-to-get-gateway-and-subnet-mask-details-in-android-programmatically">link</a>

I adapted it for my needs, and here it is:

<pre><code>private static String intToIP(int ipAddress) {
 String ret = String.format("%d.%d.%d.%d", (ipAddress &amp; 0xff),
 (ipAddress &gt;&gt; 8 &amp; 0xff), (ipAddress &gt;&gt; 16 &amp; 0xff),
 (ipAddress &gt;&gt; 24 &amp; 0xff));

 return ret;
}

public static String GetSubnetMask_WIFI() {

 WifiManager wifiManager = (WifiManager) Global.getMainActivity()
 .getSystemService(Context.WIFI_SERVICE);
 WifiInfo wifiInfo = wifiManager.getConnectionInfo();

 DhcpInfo dhcp = wifiManager.getDhcpInfo();
 String mask = intToIP(dhcp.netmask);

 return mask;
}
</code></pre>

blocks|key|1273587|text|您可以将获取的值转换为标准文本格式，如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1273588|short+prflen=...getNetworkPrefixLength();
int+shft+=+0xffffffff<<(32-prflen);
int+oct1+=+((byte)+((shft&0xff000000)>>24))+&+0xff;
int+oct2+=+((byte)+((shft&0x00ff0000)>>16))+&+0xff;
int+oct3+=+((byte)+((shft&0x0000ff00)>>8))+&+0xff;
int+oct4+=+((byte)+(shft&0x000000ff))+&+0xff;
String+submask+=+oct1%2B"."%2Boct2%2B"."%2Boct3%2B"."%2Boct4;|code-block|syntax|javascript|1273589|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|$]]

You can convert the obtained value into the standard textual format like this:

<pre><code>short prflen=...getNetworkPrefixLength();
int shft = 0xffffffff&lt;&lt;(32-prflen);
int oct1 = ((byte) ((shft&amp;0xff000000)&gt;&gt;24)) &amp; 0xff;
int oct2 = ((byte) ((shft&amp;0x00ff0000)&gt;&gt;16)) &amp; 0xff;
int oct3 = ((byte) ((shft&amp;0x0000ff00)&gt;&gt;8)) &amp; 0xff;
int oct4 = ((byte) (shft&amp;0x000000ff)) &amp; 0xff;
String submask = oct1+"."+oct2+"."+oct3+"."+oct4;
</code></pre>

blocks|key|1273630|text|总之，获取掩码的方法如下所示：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1273631|public+String+mascara()+throws+SocketException{
++++try{
++++++++InetAddress+localHost+=+Inet4Address.getLocalHost();
++++++++NetworkInterface+networkInterface+=+NetworkInterface.getByInetAddress(localHost);
++++++++prefijo+=+
++++++++++++""%2BnetworkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength();
++++++++int+shft+=+0xffffffff<<(32-+
++++++++++++++++networkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength());
++++++++int+oct1+=+((byte)+((shft&0xff000000)>>24))+&+0xff;
++++++++int+oct2+=+((byte)+((shft&0x00ff0000)>>16))+&+0xff;
++++++++int+oct3+=+((byte)+((shft&0x0000ff00)>>8))+&+0xff;
++++++++int+oct4+=+((byte)+(shft&0x000000ff))+&+0xff;
++++++++mascara+=+oct1%2B"."%2Boct2%2B"."%2Boct3%2B"."%2Boct4;
++++++++//+System.out.println(""%2Bmascara);+++++++++++
++++}catch(UnknownHostException+e){
++++++++System.out.println("Error:+"%2Be);
++++}
++++return+mascara;
}|code-block|syntax|javascript|1273632|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|$]]

In summary, a method to obtain the mask would be like this:
<pre class="lang-java prettyprint-override"><code>public String mascara() throws SocketException{
 try{
 InetAddress localHost = Inet4Address.getLocalHost();
 NetworkInterface networkInterface = NetworkInterface.getByInetAddress(localHost);
 prefijo = 
 &quot;&quot;+networkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength();
 int shft = 0xffffffff&lt;&lt;(32- 
 networkInterface.getInterfaceAddresses().get(0).getNetworkPrefixLength());
 int oct1 = ((byte) ((shft&amp;0xff000000)&gt;&gt;24)) &amp; 0xff;
 int oct2 = ((byte) ((shft&amp;0x00ff0000)&gt;&gt;16)) &amp; 0xff;
 int oct3 = ((byte) ((shft&amp;0x0000ff00)&gt;&gt;8)) &amp; 0xff;
 int oct4 = ((byte) (shft&amp;0x000000ff)) &amp; 0xff;
 mascara = oct1+&quot;.&quot;+oct2+&quot;.&quot;+oct3+&quot;.&quot;+oct4;
 // System.out.println(&quot;&quot;+mascara); 
 }catch(UnknownHostException e){
 System.out.println(&quot;Error: &quot;+e);
 }
 return mascara;
}
</code></pre>

How do you get the <code>Subnet</code> mask address of the local system using Java?

How to get subnet mask of local system using java?

Windows

Java

如何使用Java获取本地系统的Subnet掩码地址？

问如何使用java获取本地系统的子网掩码？
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