Ethernet发送过程java代码

以下是一个简单的Ethernet发送过程的Java代码示例，假设我们要发送的数据为data，源MAC地址为src_mac，目的MAC地址为dst_mac，协议类型为protocol_type，发送的网卡接口为interface_name：

import java.net.*;

public class EthernetSender {
    // 发送Ethernet帧
    public static void sendEthernetFrame(byte[] data, String srcMac, String dstMac, int protocolType, String interfaceName) throws Exception {
        // 创建Socket
        NetworkInterface ni = NetworkInterface.getByName(interfaceName);
        DatagramSocket sock = new DatagramSocket();
        sock.setBroadcast(true);
        sock.setNetworkInterface(ni);

        // 封装Ethernet帧
        byte[] dstMacBytes = hexStringToByteArray(dstMac.replace(":", ""));
        byte[] srcMacBytes = hexStringToByteArray(srcMac.replace(":", ""));
        byte[] protocolTypeBytes = new byte[2];
        protocolTypeBytes[0] = (byte) ((protocolType >> 8) & 0xff);
        protocolTypeBytes[1] = (byte) (protocolType & 0xff);
        byte[] ethernetFrame = new byte[dstMacBytes.length + srcMacBytes.length + protocolTypeBytes.length + data.length];
        System.arraycopy(dstMacBytes, 0, ethernetFrame, 0, dstMacBytes.length);
        System.arraycopy(srcMacBytes, 0, ethernetFrame, dstMacBytes.length, srcMacBytes.length);
        System.arraycopy(protocolTypeBytes, 0, ethernetFrame, dstMacBytes.length + srcMacBytes.length, protocolTypeBytes.length);
        System.arraycopy(data, 0, ethernetFrame, dstMacBytes.length + srcMacBytes.length + protocolTypeBytes.length, data.length);

        // 发送Ethernet帧
        DatagramPacket packet = new DatagramPacket(ethernetFrame, ethernetFrame.length, InetAddress.getByName("255.255.255.255"), 0);
        sock.send(packet);

        // 关闭Socket
        sock.close();
    }

    // 将十六进制字符串转换为字节数组
    private static byte[] hexStringToByteArray(String s) {
        int len = s.length();
        byte[] data = new byte[len / 2];
        for (int i = 0; i < len; i += 2) {
            data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16));
        }
        return data;
    }
}

其中，我们使用了Java的DatagramSocket和NetworkInterface类来进行Socket编程。通过NetworkInterface.getByName()方法获取指定网卡接口的NetworkInterface对象，然后创建DatagramSocket对象并将其与指定网卡接口绑定。封装Ethernet帧的过程与Python的示例代码基本相同，只是需要手动将协议类型转换为网络字节序（大端序）。最后，创建DatagramPacket对象并使用DatagramSocket.send()方法发送Ethernet帧。注意，Java的DatagramSocket类中没有提供设置网卡接口MAC地址的方法，因此无需手动设置MAC地址。