需求：应用A（通常有多个）和应用B（1个）进行 socket通讯，应用A必须知道应用B的ip地址（在应用A的配置文件中写死的），这个时候就必须把应用B的ip设成固定ip（但是某些时候如更换路由后要重新设置网络，但是操作人员不知道这个规则），就有可能造成应用A和应用B无法进行正常通讯，所以要改成应用A动态获取应用B的ip地址。
经过讨论决定采用udp协议实现，upd是一种无连接的传输层协议。应用A在不知道应用B的 ip情况下 可以使用广播地址255.255.255.255，将消息发送到在同一广播网络上的B。从而获取B的ip。
实现代码：
B应用为服务端：将udp监听放到一个线程中，当有客户端请求时就会进行响应
/**
* udp连接，用于动态ip, pos向255.255.255.255：5060发送请求即可
* **/
public class UdpServer extends Thread implements Runnable {
private final int MAX_LENGTH = 1024;
private final int PORT = 5060;
private DatagramSocket datagramSocket;
public void run() {
try {
init();
while(true){
try {
byte[] buffer = new byte[MAX_LENGTH];
DatagramPacket packet = new DatagramPacket(buffer, buffer.length);
receive(packet);
String receStr = new String(packet.getData(), 0 , packet.getLength());
System.out.println("接收数据包" + receStr);
byte[] bt = new byte[packet.getLength()];
System.arraycopy(packet.getData(), 0, bt, 0, packet.getLength());
System.out.println(packet.getAddress().getHostAddress() + "：" + packet.getPort() + "：" + Arrays.toString(bt));
packet.setData(bt);
response(packet);
} catch (Exception e) {
e.printStackTrace();
LoggerUtil.error("udp线程出现异常：" + e.toString());
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
public void receive(DatagramPacket packet) throws Exception {
datagramSocket.receive(packet);
}
public void response(DatagramPacket packet) throws Exception {
datagramSocket.send(packet);
}
/**
* 初始化连接
*/
public void init(){
try {
datagramSocket = new DatagramSocket(PORT);
System.out.println("udp服务端已经启动！");
} catch (Exception e) {
datagramSocket = null;
System.out.println("udp服务端启动失败！");
e.printStackTrace();
}
}
}
客户端：本来客户端是使用pb来实现的，但是这里使用java来模拟
/***
* UDP Client端
***/
public class UdpClient {
private String sendStr = "hello";
private String netAddress = "255.255.255.255";
private final int PORT = 5060;
private DatagramSocket datagramSocket;
private DatagramPacket datagramPacket;
public UdpClient(){
try {
datagramSocket = new DatagramSocket();
byte[] buf = sendStr.getBytes();
InetAddress address = InetAddress.getByName(netAddress);
datagramPacket = new DatagramPacket(buf, buf.length, address, PORT);
datagramSocket.send(datagramPacket);
byte[] receBuf = new byte[1024];
DatagramPacket recePacket = new DatagramPacket(receBuf, receBuf.length);
datagramSocket.receive(recePacket);
String receStr = new String(recePacket.getData(), 0 , recePacket.getLength());
//获取服务端ip
String serverIp = recePacket.getAdress();
} catch (SocketException e) {
e.printStackTrace();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
// 关闭socket
if(datagramSocket != null){
datagramSocket.close();
}
}
}
public static void main(String[] args) {
for (int i = 0; i < 100; i++) {
new Thread(new Runnable() {
@Override
public void run() {
UdpClient udpClient = new UdpClient();
}
}).start();
}
}
}
