Trail: Custom Networking
Lesson: Programmatic Access to Network Parameters

网络接口参数

你可以访问超出分配给它的名称和 IP 地址的网络接口的网络参数

你可以使用 isUP() 方法发现网络接口是“up”(即运行)。以下方法指示网络接口类型：

isLoopback() 表示网络接口是否为环回接口。
isPointToPoint() 表示接口是否为点对点接口。
isVirtual() 表示接口是否为虚拟接口。

supportsMulticast() 方法指示网络接口是否支持多播。getHardwareAddress() 方法返回网络接口的物理硬件地址（通常称为 MAC 地址）。getMTU() 方法返回最大传输单元(MTU)，这是最大的数据包大小。

以下示例通过添加此页面中描述的其他网络参数来扩展 Listing Network Interface Addresses 中的示例：

import java.io.*;
import java.net.*;
import java.util.*;
import static java.lang.System.out;

public class ListNetsEx {

    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: %s\n", netint.getDisplayName());
        out.printf("Name: %s\n", netint.getName());
        Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
        
        for (InetAddress inetAddress : Collections.list(inetAddresses)) {
            out.printf("InetAddress: %s\n", inetAddress);
        }
       
        out.printf("Up? %s\n", netint.isUp());
        out.printf("Loopback? %s\n", netint.isLoopback());
        out.printf("PointToPoint? %s\n", netint.isPointToPoint());
        out.printf("Supports multicast? %s\n", netint.supportsMulticast());
        out.printf("Virtual? %s\n", netint.isVirtual());
        out.printf("Hardware address: %s\n",
                    Arrays.toString(netint.getHardwareAddress()));
        out.printf("MTU: %s\n", netint.getMTU());
        out.printf("\n");
     }
}

以下是示例程序的示例输出：

Display name: bge0
Name: bge0
InetAddress: /fe80:0:0:0:203:baff:fef2:e99d%2
InetAddress: /129.156.225.59
Up? true
Loopback? false
PointToPoint? false
Supports multicast? false
Virtual? false
Hardware address: [0, 3, 4, 5, 6, 7]
MTU: 1500

Display name: lo0
Name: lo0
InetAddress: /0:0:0:0:0:0:0:1%1
InetAddress: /127.0.0.1
Up? true
Loopback? true
PointToPoint? false
Supports multicast? false
Virtual? false
Hardware address: null
MTU: 8232