如何从java中的ip地址获取子网

Question

我得到了ip（ipv4，如192.168.161.125），我怎样才能获得我的电脑所在的子网？首选java方法和String格式结果。

子网是使用IP地址和子网掩码计算的网络

谢谢。

Answer 1

这就是你在Java中的表现，

import java.util.ArrayList;
import java.util.List;

public class IPv4 {
    int baseIPnumeric;
    int netmaskNumeric;
    public IPv4(String symbolicIP, String netmask) throws NumberFormatException {

        /* IP */
        String[] st = symbolicIP.split("\\.");

        if (st.length != 4)
            throw new NumberFormatException("Invalid IP address: " + symbolicIP);

        int i = 24;
        baseIPnumeric = 0;

        for (int n = 0; n < st.length; n++) {

            int value = Integer.parseInt(st[n]);

            if (value != (value & 0xff)) {

                throw new NumberFormatException("Invalid IP address: "+ symbolicIP);
            }

            baseIPnumeric += value << i;
            i -= 8;
        }

        /* Netmask */
        st = netmask.split("\\.");

        if (st.length != 4)
            throw new NumberFormatException("Invalid netmask address: "

                    + netmask);

        i = 24;
        netmaskNumeric = 0;

        if (Integer.parseInt(st[0]) < 255) {

            throw new NumberFormatException(
                    "The first byte of netmask can not be less than 255");
        }
        for (int n = 0; n < st.length; n++) {

            int value = Integer.parseInt(st[n]);

            if (value != (value & 0xff)) {

                throw new NumberFormatException("Invalid netmask address: "  + netmask);
            }

            netmaskNumeric += value << i;
            i -= 8;

        }
/*
* see if there are zeroes inside netmask, like: 1111111101111 This is
* illegal, throw exception if encountered. Netmask should always have
* only ones, then only zeroes, like: 11111111110000
*/
        boolean encounteredOne = false;
        int ourMaskBitPattern = 1;

        for (i = 0; i < 32; i++) {

            if ((netmaskNumeric & ourMaskBitPattern) != 0) {

                encounteredOne = true; // the bit is 1
            } else { // the bit is 0
                if (encounteredOne == true)

                    throw new NumberFormatException("Invalid netmask: " + netmask + " (bit " + (i + 1) + ")");
            }

            ourMaskBitPattern = ourMaskBitPattern << 1;
        }
    }

/**
* Specify IP in CIDR format like: new IPv4("10.1.0.25/16");
*
*@param IPinCIDRFormat
*/
    public IPv4(String IPinCIDRFormat) throws NumberFormatException {

        String[] st = IPinCIDRFormat.split("\\/");
        if (st.length != 2)

            throw new NumberFormatException("Invalid CIDR format '"
                    + IPinCIDRFormat + "', should be: xx.xx.xx.xx/xx");

        String symbolicIP = st[0];
        String symbolicCIDR = st[1];

        Integer numericCIDR = new Integer(symbolicCIDR);
        if (numericCIDR > 32)

            throw new NumberFormatException("CIDR can not be greater than 32");

        /* IP */
        st = symbolicIP.split("\\.");

        if (st.length != 4)
            throw new NumberFormatException("Invalid IP address: " + symbolicIP);

        int i = 24;
        baseIPnumeric = 0;

        for (int n = 0; n < st.length; n++) {

            int value = Integer.parseInt(st[n]);

            if (value != (value & 0xff)) {

                throw new NumberFormatException("Invalid IP address: " + symbolicIP);
            }

            baseIPnumeric += value << i;
            i -= 8;

        }

        /* netmask from CIDR */
        if (numericCIDR < 8)
            throw new NumberFormatException("Netmask CIDR can not be less than 8");
        netmaskNumeric = 0xffffffff;
        netmaskNumeric = netmaskNumeric << (32 - numericCIDR);

    }

    /**
* Get the IP in symbolic form, i.e. xxx.xxx.xxx.xxx
*
*@return
*/
    public String getIP() {
        return convertNumericIpToSymbolic(baseIPnumeric);

    }

    private String convertNumericIpToSymbolic(Integer ip) {
        StringBuffer sb = new StringBuffer(15);

        for (int shift = 24; shift > 0; shift -= 8) {

            // process 3 bytes, from high order byte down.
            sb.append(Integer.toString((ip >>> shift) & 0xff));

            sb.append('.');
        }
        sb.append(Integer.toString(ip & 0xff));

        return sb.toString();
    }

/**
* Get the net mask in symbolic form, i.e. xxx.xxx.xxx.xxx
*
*@return
*/

    public String getNetmask() {
        StringBuffer sb = new StringBuffer(15);

        for (int shift = 24; shift > 0; shift -= 8) {

            // process 3 bytes, from high order byte down.
            sb.append(Integer.toString((netmaskNumeric >>> shift) & 0xff));

            sb.append('.');
        }
        sb.append(Integer.toString(netmaskNumeric & 0xff));

        return sb.toString();
    }

/**
* Get the IP and netmask in CIDR form, i.e. xxx.xxx.xxx.xxx/xx
*
*@return
*/

    public String getCIDR() {
        int i;
        for (i = 0; i < 32; i++) {

            if ((netmaskNumeric << i) == 0)
                break;

        }
        return convertNumericIpToSymbolic(baseIPnumeric & netmaskNumeric) + "/" + i;
    }

/**
* Get an arry of all the IP addresses available for the IP and netmask/CIDR
* given at initialization
*
*@return
*/
    public List<String> getAvailableIPs(Integer numberofIPs) {

        ArrayList<String> result = new ArrayList<String>();
        int numberOfBits;

        for (numberOfBits = 0; numberOfBits < 32; numberOfBits++) {

            if ((netmaskNumeric << numberOfBits) == 0)
                break;

        }
        Integer numberOfIPs = 0;
        for (int n = 0; n < (32 - numberOfBits); n++) {

            numberOfIPs = numberOfIPs << 1;
            numberOfIPs = numberOfIPs | 0x01;

        }

        Integer baseIP = baseIPnumeric & netmaskNumeric;

        for (int i = 1; i < (numberOfIPs) && i < numberofIPs; i++) {

            Integer ourIP = baseIP + i;

            String ip = convertNumericIpToSymbolic(ourIP);

            result.add(ip);
        }
        return result;
    }

/**
* Range of hosts
*
*@return
*/
    public String getHostAddressRange() {

        int numberOfBits;
        for (numberOfBits = 0; numberOfBits < 32; numberOfBits++) {

            if ((netmaskNumeric << numberOfBits) == 0)
                break;
        }
        Integer numberOfIPs = 0;
        for (int n = 0; n < (32 - numberOfBits); n++) {

            numberOfIPs = numberOfIPs << 1;
            numberOfIPs = numberOfIPs | 0x01;

        }

        Integer baseIP = baseIPnumeric & netmaskNumeric;
        String firstIP = convertNumericIpToSymbolic(baseIP + 1);
        String lastIP = convertNumericIpToSymbolic(baseIP + numberOfIPs - 1);
        return firstIP + " - " + lastIP;
    }

/**
* Returns number of hosts available in given range
*
*@return number of hosts
*/
    public Long getNumberOfHosts() {
        int numberOfBits;

        for (numberOfBits = 0; numberOfBits < 32; numberOfBits++) {

            if ((netmaskNumeric << numberOfBits) == 0)
                break;

        }

        Double x = Math.pow(2, (32 - numberOfBits));

        if (x == -1)
            x = 1D;

        return x.longValue();
    }

/**
* The XOR of the netmask
*
*@return wildcard mask in text form, i.e. 0.0.15.255
*/

    public String getWildcardMask() {
        Integer wildcardMask = netmaskNumeric ^ 0xffffffff;

        StringBuffer sb = new StringBuffer(15);
        for (int shift = 24; shift > 0; shift -= 8) {

            // process 3 bytes, from high order byte down.
            sb.append(Integer.toString((wildcardMask >>> shift) & 0xff));

            sb.append('.');
        }
        sb.append(Integer.toString(wildcardMask & 0xff));

        return sb.toString();

    }

    public String getBroadcastAddress() {

        if (netmaskNumeric == 0xffffffff)
            return "0.0.0.0";

        int numberOfBits;
        for (numberOfBits = 0; numberOfBits < 32; numberOfBits++) {

            if ((netmaskNumeric << numberOfBits) == 0)
                break;

        }
        Integer numberOfIPs = 0;
        for (int n = 0; n < (32 - numberOfBits); n++) {

            numberOfIPs = numberOfIPs << 1;
            numberOfIPs = numberOfIPs | 0x01;
        }

        Integer baseIP = baseIPnumeric & netmaskNumeric;
        Integer ourIP = baseIP + numberOfIPs;

        String ip = convertNumericIpToSymbolic(ourIP);

        return ip;
    }

    private String getBinary(Integer number) {
        String result = "";

        Integer ourMaskBitPattern = 1;
        for (int i = 1; i <= 32; i++) {

            if ((number & ourMaskBitPattern) != 0) {

                result = "1" + result; // the bit is 1
            } else { // the bit is 0

                result = "0" + result;
            }
            if ((i % 8) == 0 && i != 0 && i != 32)

                result = "." + result;
            ourMaskBitPattern = ourMaskBitPattern << 1;

        }
        return result;
    }

    public String getNetmaskInBinary() {

        return getBinary(netmaskNumeric);
    }

/**
* Checks if the given IP address contains in subnet
*
*@param IPaddress
*@return
*/
    public boolean contains(String IPaddress) {

        Integer checkingIP = 0;
        String[] st = IPaddress.split("\\.");

        if (st.length != 4)
            throw new NumberFormatException("Invalid IP address: " + IPaddress);

        int i = 24;
        for (int n = 0; n < st.length; n++) {

            int value = Integer.parseInt(st[n]);

            if (value != (value & 0xff)) {

                throw new NumberFormatException("Invalid IP address: "
                        + IPaddress);
            }

            checkingIP += value << i;
            i -= 8;
        }

        if ((baseIPnumeric & netmaskNumeric) == (checkingIP & netmaskNumeric))

            return true;
        else
            return false;
    }

    public boolean contains(IPv4 child) {

        Integer subnetID = child.baseIPnumeric;

        Integer subnetMask = child.netmaskNumeric;

        if ((subnetID & this.netmaskNumeric) == (this.baseIPnumeric & this.netmaskNumeric)) {

            if ((this.netmaskNumeric < subnetMask) == true
                    && this.baseIPnumeric <= subnetID) {

                return true;
            }

        }
        return false;

    }
/**
*@param args
*/
    public static void main(String[] args) { 
    IPv4 ipv4 = new IPv4("192.168.161.125/30"); //30 is the CIDR  for Mask 255.255.255.252
    System.out.println(ipv4.getCIDR());
    System.out.println(ipv4.getNetmask());
    System.out.println(ipv4.getNumberOfHosts());
    System.out.println(ipv4.getWildcardMask());
    System.out.println(ipv4.getBroadcastAddress());
    System.out.println(ipv4.getHostAddressRange());

    }
}

Answer 2

一个简单的方法。假设我们将子网掩码和ip地址分为2个字符串：

String[] mask      = subnetMaskString.split("\\.");
String[] ipAddress = ipAddressString.split("\\.");
StringBuffer ipSubnet  = new StringBuffer();
for(int i=0; i<4; i++)
    try{
        if(ipSubnet.length()>0)
            ipSubnet.append('.');
        ipSubnet.append(Integer.parseInt(ipAddress[i]) & Integer.parseInt(mask[i]));
    }catch(Exception x){ 
        //Integer parsing exception, wrong ipaddress or mask
        break;
    }
// if no exception ipSubnet.toString() is the subnet ip //

Answer 3

The IPAddress Java library以多态方式支持IPv4和IPv6子网。免责声明：我是项目经理。

以下是您的示例的示例代码，地址为192.168.161.125，子网掩码为255.255.255.252。它显示了三种方法。

第一种方法解析字符串addr / mask：

public static String getNetwork1(String addrStr, String maskStr) throws AddressStringException {
    IPAddressString addrString = new IPAddressString(addrStr + IPAddress.PREFIX_LEN_SEPARATOR + maskStr);
    IPAddress addr = addrString.toAddress();
    IPAddress subnet = addr.toPrefixBlock();
    return subnet.toString();
}

第二种方法掩盖地址以获取网络：

public static String getNetwork2(String addrStr, String maskStr) throws AddressStringException {
    IPAddressString addrString = new IPAddressString(addrStr);
    IPAddressString maskString = new IPAddressString(maskStr);
    IPAddress addr = addrString.toAddress();
    IPAddress mask = maskString.toAddress();
    IPAddress masked = addr.mask(mask);
    return masked.toString();
}

第三种方法从掩码中获取前缀长度以获取网络：

public static String getNetwork3(String addrStr, String maskStr) throws AddressStringException {
    IPAddressString addrString = new IPAddressString(addrStr);
    IPAddressString maskString = new IPAddressString(maskStr);
    IPAddress addr = addrString.toAddress();
    IPAddress mask = maskString.toAddress();
    Integer prefLen = mask.getBlockMaskPrefixLength(true);
    IPAddress subnet = addr.setPrefixLength(prefLen).toPrefixBlock();
    return subnet.toString();
}

使用三个选项：

String addrString = "192.168.161.125";
String maskString = "255.255.255.252";
System.out.println(getNetwork1(addrString, maskString));
System.out.println(getNetwork2(addrString, maskString));
System.out.println(getNetwork3(addrString, maskString));

我们得到输出：

192.168.161.124/30
192.168.161.124
192.168.161.124/30

要删除第一个和第三个地址结果的前缀长度，可以使用withoutPrefixLength（）。