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Network Interface in Java

Posted by Abhishek Dubey Articles | Java February 23, 2012
In this article we describe how you can access Network Interface information using Java and the meaning of Network Interface.
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 Network Interface in Java

A network interface is the point of interconnection between a computer and a private or public network. A network interface is generally a network interface card (NIC). Java 1.4 introduced NetworkInterface Class to get the details of a local network interface, MAC address of the Interface, MTU (maximum transmission unit) of the Interface, list of IP address attached to the interface whether the interface up and/or down and whether it supports multicasting etc.

NetworkInterface is useful for a multihomed system, which is a system with multiple NICs. Using NetworkInterface, you can specify which NIC to use for a particular network activity. The NetworkInterface class is given by Java in a package named java.net and the NetworkInterface class represents both types of interfaces.

Example

The loop back interface (127.0.0.1 for IPv4 and 1 for IPv6) is not a physical device but a piece of software simulating a network interface. The loop back interface is commonly used in test enviorments.

code

import java.net.*;

import java.io.*;

import java.net.*;

import java.util.*;

public class DemoNetworkInterface

{

private static final String NL = System.getProperty("line.separator");

private static final String NL_TAB = NL + "  ";

private static final String IPV4 = "IPv4";

private static final String IPV6 = "IPv6";

 

private static class MyInterface

{

public String displayName;

public String name;

public int mtu;

public boolean isUp;

public boolean isLoopback;

public boolean isPointToPoint; // e.g. a PPP modem interface

public boolean isVirtual;      // a sub-interface

public boolean supportsMulticast;

public byte[] macAddress;

public List<MyIpAddress> ipAddresses;

public List<MyInterface> subInterfaces;

 

public String toString()

{

StringBuilder sb = new StringBuilder(NL);

sb.append("*** Interface [" + name + "] ***").append(NL);

sb.append(NL).append("Name  : " + displayName);

sb.append(NL).append("MTU           : " + mtu);

sb.append(NL).append("Loop back     : " + isLoopback);

sb.append(NL).append("Point to Point: " + isPointToPoint);

sb.append(NL).append(" InterFace is up    : " + isUp);

sb.append(NL).append("virtual       : " + isVirtual);

sb.append(NL).append("multicast     : " + supportsMulticast);

sb.append(NL).append("MAC address  : ");

if (macAddress != null)

{

for (byte b : macAddress)

{

sb.append(String.format("%1$02X ", b));

}

}

else

{

sb.append("n/a");

}

for (MyIpAddress ipAddr: ipAddresses)

{

sb.append(ipAddr);

}

for (MyInterface subInfo: subInterfaces)

{

sb.append(subInfo);

}

return sb.toString();

}

}

private static class MyIpAddress

{

public String ipAddress;

public String ipVersion = "unknown";

public String hostName;

public String canonicalHostName;

public boolean isLoopback;

public boolean isSiteLocal; // private IP address

public boolean isAnyLocal// wildcard address

public boolean isLinkLocal;

public boolean isMulticast;

public boolean isReachable;

public String toString()

{

StringBuilder sb = new StringBuilder();

sb.append(NL).append("INET address ("+ ipVersion + "): " + ipAddress);

sb.append(NL_TAB).append("host name           : " + hostName);

sb.append(NL_TAB).append("canonical host name : " + canonicalHostName);

sb.append(NL_TAB).append("loopback        : " + isLoopback);

sb.append(NL_TAB).append("site local        : " + isSiteLocal);

sb.append(NL_TAB).append("any local        : " + isAnyLocal);

sb.append(NL_TAB).append("link local         : " + isLinkLocal);

sb.append(NL_TAB).append("multicast        : " + isMulticast);

sb.append(NL_TAB).append("reachable       : " + isReachable);

return sb.toString();

}

}

private static MyInterface getMyInterface(NetworkInterface nif) throws IOException

{

// get interface information

MyInterface info = new MyInterface();

info.displayName = nif.getDisplayName();

info.name = nif.getName();

info.mtu = nif.getMTU();

info.isUp = nif.isUp();

info.isLoopback = nif.isLoopback();

info.isPointToPoint = nif.isPointToPoint();

info.isVirtual = nif.isVirtual();

info.supportsMulticast = nif.supportsMulticast();

info.macAddress = nif.getHardwareAddress();

info.ipAddresses = new ArrayList<MyIpAddress>();

info.subInterfaces = new ArrayList<MyInterface>();

// get IP address information

Enumeration<InetAddress> inetAddresses = nif.getInetAddresses();

while (inetAddresses.hasMoreElements())

{

InetAddress inetAddr = inetAddresses.nextElement();

MyIpAddress ipInfo = new MyIpAddress();

if (inetAddr instanceof Inet4Address)

{

ipInfo.ipVersion = IPV4;

}

else if (inetAddr instanceof Inet6Address)

{

ipInfo.ipVersion = IPV6;

}

ipInfo.ipAddress = inetAddr.getHostAddress();

ipInfo.hostName = inetAddr.getHostName();

ipInfo.canonicalHostName = inetAddr.getCanonicalHostName();

ipInfo.isAnyLocal = inetAddr.isAnyLocalAddress();

ipInfo.isLinkLocal = inetAddr.isLinkLocalAddress();

ipInfo.isSiteLocal = inetAddr.isSiteLocalAddress();

ipInfo.isLoopback = inetAddr.isLoopbackAddress();

ipInfo.isMulticast = inetAddr.isMulticastAddress();

ipInfo.isReachable = inetAddr.isReachable(5000);

info.ipAddresses.add(ipInfo);

}

// get virtual interface information

Enumeration<NetworkInterface> subIfs = nif.getSubInterfaces();

while (subIfs.hasMoreElements())

{

NetworkInterface subIf = subIfs.nextElement();

MyInterface subInfo = getMyInterface(subIf);

info.subInterfaces.add(subInfo);

}

return info;

}

public static void main(String[] args) throws IOException

{

Enumeration<NetworkInterface> interfaces =

NetworkInterface.getNetworkInterfaces();

 while (interfaces.hasMoreElements())

{

NetworkInterface nif = interfaces.nextElement();

System.out.println(getMyInterface(nif));

}

}

}

Output

The following output provides many information from the NIC (Network Interface Card) of your system.

cmd1.jpg

Resource

Java naming and directory interface(JNDI)

Interfaces of collection in JAVA

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