change.java

基于java的stun服务器和客户端 实现了关于stun防火墙探测

package com.stun.tool;

public class Change {

	/**
	 * 把一个整形该为byte
	 * @param value
	 * @return
	 * @throws Exception
	 */
	public byte integerToOneByte(int value) throws Exception {
		if ((value > Math.pow(2, 15)) || (value < 0)) {
			throw new Exception("Integer value " + value
					+ " is larger than 2^15");
		}
		return (byte) (value & 0xFF);
	}

	/**
	 * 把一个整形改为2位的byte数组
	 * @param value
	 * @return
	 * @throws Exception
	 */
	public byte[] integerToTwoBytes(int value) throws Exception {
		byte[] result = new byte[2];
		if ((value > Math.pow(2, 31)) || (value < 0)) {
			throw new Exception("Integer value " + value
					+ " is larger than 2^31");
		}
		result[0] = (byte) ((value >>> 8) & 0xFF);
		result[1] = (byte) (value & 0xFF);
		return result;
	}

	/**
	 * 把一个整形改为4位的byte数组
	 * @param value
	 * @return
	 * @throws Exception
	 */
	public byte[] integerToFourBytes(int value) throws Exception {
		byte[] result = new byte[4];
		if ((value > Math.pow(2, 63)) || (value < 0)) {
			throw new Exception("Integer value " + value
					+ " is larger than 2^63");
		}
		result[0] = (byte) ((value >>> 24) & 0xFF);
		result[1] = (byte) ((value >>> 16) & 0xFF);
		result[2] = (byte) ((value >>> 8) & 0xFF);
		result[3] = (byte) (value & 0xFF);
		return result;
	}

	/**
	 * 把一个byte转化位整形
	 * @param value
	 * @return
	 * @throws Exception
	 */
	public int oneByteToInteger(byte value) throws Exception {
		return (int) value & 0xFF;
	}

	/**
	 * 把一个2位的数组转化位整形
	 * @param value
	 * @return
	 * @throws Exception
	 */
	public int twoBytesToInteger(byte[] value) throws Exception {
		if (value.length < 2) {
			throw new Exception("Byte array too short!");
		}
		int temp0 = value[0] & 0xFF;
		int temp1 = value[1] & 0xFF;
		return ((temp0 << 8) + temp1);
	}

	/**
	 * 把一个4位的数组转化位整形
	 * @param value
	 * @return
	 * @throws Exception
	 */
	public long fourBytesToLong(byte[] value) throws Exception {
		if (value.length < 4) {
			throw new Exception("Byte array too short!");
		}
		int temp0 = value[0] & 0xFF;
		int temp1 = value[1] & 0xFF;
		int temp2 = value[2] & 0xFF;
		int temp3 = value[3] & 0xFF;
		return (((long) temp0 << 24) + (temp1 << 16) + (temp2 << 8) + temp3);
	}

	/**
	 * 得到一个消息ID
	 * @return
	 * @throws Exception
	 */
	public byte[] generateTransactionID() throws Exception {
		byte[] id = new byte[16];
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 0, 2);
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 2, 2);
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 4, 2);
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 6, 2);
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 8, 2);
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 10, 2);
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 12, 2);
		System.arraycopy(integerToTwoBytes((int) (Math.random() * 65536)), 0,
				id, 14, 2);
		return id;
	}

	/**
	 * 把IP拆分位int数组
	 * @param ip
	 * @return
	 * @throws Exception
	 */
	public int[] getIntIPValue(String ip) throws Exception {
		String[] sip = ip.split("[.]");
		if (sip.length != 4) {
			throw new Exception("error IPAddress");
		}
		int[] intIP = { Integer.parseInt(sip[0]), Integer.parseInt(sip[1]),
				Integer.parseInt(sip[2]), Integer.parseInt(sip[3]) };
		return intIP;
	}

	/**
	 * 把byte类型IP地址转化位字符串
	 * @param address
	 * @return
	 * @throws Exception
	 */
	public String getStringIPValue(byte[] address) throws Exception {
		if (address.length != 4) {
			throw new Exception("error IPaddress");
		}
		int first = this.oneByteToInteger(address[0]);
		int second = this.oneByteToInteger(address[1]);
		int third = this.oneByteToInteger(address[2]);
		int fourth = this.oneByteToInteger(address[3]);

		return first + "." + second + "." + third + "." + fourth;
	}
	/**
	 * 读取消息地址
	 * @param message
	 * @param index
	 * @param port
	 * @param address
	 */
	public void getAddress(byte[] message, int index, byte[] port,
			byte[] address) {
		System.arraycopy(message, index + 22,
				port, 0, 2);
		System.arraycopy(message, index + 24,
				address, 0, 4);
	}
}