JAVA-UDP辅助TCP实现点对点传输
public class ServerInfo {
private String sn;
private int port;
private String address;
public ServerInfo(int port, String ip, String sn) {
this.port = port;
this.address = ip;
this.sn = sn;
}
public String getSn() {
return sn;
}
public void setSn(String sn) {
this.sn = sn;
}
public int getPort() {
return port;
}
public void setPort(int port) {
this.port = port;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "ServerInfo{" +
"sn='" + sn + '\'' +
", port=" + port +
", address='" + address + '\'' +
'}';
}
}
客户端：
public class Client {
public static void main(String[] args) {
ServerInfo info = ClientSearcher.searchServer(10000);
System.out.println("Server:" + info);
}
}
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
public class ClientSearcher {
private static final int LISTEN_PORT = UDPConstants.PORT_CLIENT_RESPONSE;
public static ServerInfo searchServer(int timeout) {
System.out.println("UDPSearcher Started.");
// 成功收到回送的栅栏
CountDownLatch receiveLatch = new CountDownLatch(1);
Listener listener = null;
try {
listener = listen(receiveLatch);
sendBroadcast();
receiveLatch.await(timeout, TimeUnit.MILLISECONDS);
} catch (Exception e) {
e.printStackTrace();
}
// 完成
System.out.println("UDPSearcher Finished.");
if (listener == null) {
return null;
}
List<ServerInfo> devices = listener.getServerAndClose();
if (devices.size() > 0) {
return devices.get(0);
}
return null;
}
private static Listener listen(CountDownLatch receiveLatch) throws InterruptedException {
System.out.println("UDPSearcher start listen.");
CountDownLatch startDownLatch = new CountDownLatch(1);
Listener listener = new Listener(LISTEN_PORT, startDownLatch, receiveLatch);
listener.start();
startDownLatch.await();
return listener;
}
private static void sendBroadcast() throws IOException {
System.out.println("UDPSearcher sendBroadcast started.");
// 作为搜索方，让系统自动分配端口
DatagramSocket ds = new DatagramSocket();
// 构建一份请求数据
ByteBuffer byteBuffer = ByteBuffer.allocate(128);
// 头部
byteBuffer.put(UDPConstants.HEADER);
// CMD命名
byteBuffer.putShort((short) 1);
// 回送端口信息
byteBuffer.putInt(LISTEN_PORT);
// 直接构建packet
DatagramPacket requestPacket = new DatagramPacket(byteBuffer.array(),
byteBuffer.position() + 1);
// 广播地址
requestPacket.setAddress(InetAddress.getByName("255.255.255.255"));
// 设置服务器端口
requestPacket.setPort(UDPConstants.PORT_SERVER);
// 发送
ds.send(requestPacket);
ds.close();
// 完成
System.out.println("UDPSearcher sendBroadcast finished.");
}
private static class Listener extends Thread {
private final int listenPort;
private final CountDownLatch startDownLatch;
private final CountDownLatch receiveDownLatch;
private final List<ServerInfo> serverInfoList = new ArrayList<>();
private final byte[] buffer = new byte[128];
private final int minLen = UDPConstants.HEADER.length + 2 + 4;
private boolean done = false;
private DatagramSocket ds = null;
private Listener(int listenPort, CountDownLatch startDownLatch, CountDownLatch receiveDownLatch) {
super();
this.listenPort = listenPort;
this.startDownLatch = startDownLatch;
this.receiveDownLatch = receiveDownLatch;
}
@Override
public void run() {
super.run();
// 通知已启动
startDownLatch.countDown();
try {
// 监听回送端口
ds = new DatagramSocket(listenPort);
// 构建接收实体
DatagramPacket receivePack = new DatagramPacket(buffer, buffer.length);
while (!done) {
// 接收
ds.receive(receivePack);
// 打印接收到的信息与发送者的信息
// 发送者的IP地址
String ip = receivePack.getAddress().getHostAddress();
int port = receivePack.getPort();
int dataLen = receivePack.getLength();
byte[] data = receivePack.getData();
boolean isValid = dataLen >= minLen
&& ByteUtils.startsWith(data, UDPConstants.HEADER);
System.out.println("UDPSearcher receive form ip:" + ip
+ "\tport:" + port + "\tdataValid:" + isValid);
if (!isValid) {
// 无效继续
continue;
}
ByteBuffer byteBuffer = ByteBuffer.wrap(buffer, UDPConstants.HEADER.length, dataLen);
final short cmd = byteBuffer.getShort();
final int serverPort = byteBuffer.getInt();
if (cmd != 2 || serverPort <= 0) {
System.out.println("UDPSearcher receive cmd:" + cmd + "\tserverPort:" + serverPort);
continue;
}
String sn = new String(buffer, minLen, dataLen - minLen);
ServerInfo info = new ServerInfo(serverPort, ip, sn);
serverInfoList.add(info);
// 成功接收到一份
receiveDownLatch.countDown();
}
} catch (Exception ignored) {
} finally {
close();
}
System.out.println("UDPSearcher listener finished.");
}
private void close() {
if (ds != null) {
ds.close();
ds = null;
}
}
List<ServerInfo> getServerAndClose() {
done = true;
close();
return serverInfoList;
}
}
}
帮助类：
public class ByteUtils {
/**
* Does this byte array begin with match array content?
*
* @param source Byte array to examine
* @param match Byte array to locate in <code>source</code>
* @return true If the starting bytes are equal
*/
public static boolean startsWith(byte[] source, byte[] match) {
return startsWith(source, 0, match);
}
/**
* Does this byte array begin with match array content?
*
* @param source Byte array to examine
* @param offset An offset into the <code>source</code> array
* @param match Byte array to locate in <code>source</code>
* @return true If the starting bytes are equal
*/
public static boolean startsWith(byte[] source, int offset, byte[] match) {
if (match.length > (source.length - offset)) {
return false;
}
for (int i = 0; i < match.length; i++) {
if (source[offset + i] != match[i]) {
return false;
}
}
return true;
}
/**
* Does the source array equal the match array?
*
* @param source Byte array to examine
* @param match Byte array to locate in <code>source</code>
* @return true If the two arrays are equal
*/
public static boolean equals(byte[] source, byte[] match) {
if (match.length != source.length) {
return false;
}
return startsWith(source, 0, match);
}
/**
* Copies bytes from the source byte array to the destination array
*
* @param source The source array
* @param srcBegin Index of the first source byte to copy
* @param srcEnd Index after the last source byte to copy
* @param destination The destination array
* @param dstBegin The starting offset in the destination array
*/
public static void getBytes(byte[] source, int srcBegin, int srcEnd, byte[] destination,
int dstBegin) {
System.arraycopy(source, srcBegin, destination, dstBegin, srcEnd - srcBegin);
}
/**
* Return a new byte array containing a sub-portion of the source array
*
* @param srcBegin The beginning index (inclusive)
* @param srcEnd The ending index (exclusive)
* @return The new, populated byte array
*/
public static byte[] subbytes(byte[] source, int srcBegin, int srcEnd) {
byte destination[];
destination = new byte[srcEnd - srcBegin];
getBytes(source, srcBegin, srcEnd, destination, 0);
return destination;
}
/**
* Return a new byte array containing a sub-portion of the source array
*
* @param srcBegin The beginning index (inclusive)
* @return The new, populated byte array
*/
public static byte[] subbytes(byte[] source, int srcBegin) {
return subbytes(source, srcBegin, source.length);
}
}
public class TCPConstants {
// 服务器固化UDP接收端口
public static int PORT_SERVER = 30401;
}
public class UDPConstants {
// 公用头部
public static byte[] HEADER = new byte[]{7, 7, 7, 7, 7, 7, 7, 7};
// 服务器固化UDP接收端口
public static int PORT_SERVER=30201;
// 客户端回送端口
public static int PORT_CLIENT_RESPONSE = 30202;
}
import java.io.IOException;
public class Server {
public static void main(String[] args) {
ServerProvider.start(TCPConstants.PORT_SERVER);
try {
System.in.read();
}catch (IOException e) {
e.printStackTrace();
}
ServerProvider.stop();
}
}
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.nio.ByteBuffer;
import java.util.UUID;
public class ServerProvider {
private static Provider PROVIDER_INSTANCE;
static void start(int port) {
stop();
String sn = UUID.randomUUID().toString();
Provider provider = new Provider(sn, port);
provider.start();
PROVIDER_INSTANCE = provider;
}
static void stop() {
if (PROVIDER_INSTANCE != null) {
PROVIDER_INSTANCE.exit();
PROVIDER_INSTANCE = null;
}
}
private static class Provider extends Thread {
private final byte[] sn;
private final int port;
private boolean done = false;
private DatagramSocket ds = null;
// 存储消息的Buffer
final byte[] buffer = new byte[128];
Provider(String sn, int port) {
super();
this.sn = sn.getBytes();
this.port = port;
}
@Override
public void run() {
super.run();
System.out.println("UDPProvider Started.");
try {
// 监听20000 端口
ds = new DatagramSocket(UDPConstants.PORT_SERVER);
// 接收消息的Packet
DatagramPacket receivePack = new DatagramPacket(buffer, buffer.length);
while (!done) {
// 接收
ds.receive(receivePack);
// 打印接收到的信息与发送者的信息
// 发送者的IP地址
String clientIp = receivePack.getAddress().getHostAddress();
int clientPort = receivePack.getPort();
int clientDataLen = receivePack.getLength();
byte[] clientData = receivePack.getData();
boolean isValid = clientDataLen >= (UDPConstants.HEADER.length + 2 + 4)
&& ByteUtils.startsWith(clientData, UDPConstants.HEADER);
System.out.println("ServerProvider receive form ip:" + clientIp
+ "\tport:" + clientPort + "\tdataValid:" + isValid);
if (!isValid) {
// 无效继续
continue;
}
// 解析命令与回送端口
int index = UDPConstants.HEADER.length;
short cmd = (short) ((clientData[index++] << 8) | (clientData[index++] & 0xff));
int responsePort = (((clientData[index++]) << 24) |
((clientData[index++] & 0xff) << 16) |
((clientData[index++] & 0xff) << 8) |
((clientData[index] & 0xff)));
// 判断合法性
if (cmd == 1 && responsePort > 0) {
// 构建一份回送数据
ByteBuffer byteBuffer = ByteBuffer.wrap(buffer);
byteBuffer.put(UDPConstants.HEADER);
byteBuffer.putShort((short) 2);
byteBuffer.putInt(port);
byteBuffer.put(sn);
int len = byteBuffer.position();
// 直接根据发送者构建一份回送信息
DatagramPacket responsePacket = new DatagramPacket(buffer,
len,
receivePack.getAddress(),
responsePort);
ds.send(responsePacket);
System.out.println("ServerProvider response to:" + clientIp + "\tport:" + responsePort + "\tdataLen:" + len);
} else {
System.out.println("ServerProvider receive cmd nonsupport; cmd:" + cmd + "\tport:" + port);
}
}
} catch (Exception ignored) {
} finally {
close();
}
// 完成
System.out.println("UDPProvider Finished.");
}
private void close() {
if (ds != null) {
ds.close();
ds = null;
}
}
/**
* 提供结束
*/
void exit() {
done = true;
close();
}
}
}
