为什么receive（）方法不从客户端接收数据？

Question

I wrote small client-server application. It should send one string from client to server and server should show it on console. But server waits for data all time. It looks like data don't come to server. What did i wrong?

public class UDPClient {

    public static void main(String[] args) throws IOException {
        BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
        DatagramSocket clientSocket = new DatagramSocket();
        InetAddress IPAdress = InetAddress.getByName("localhost");
        byte[] sendData = new byte[1024];
        String sentence = inFromUser.readLine();
        sendData = sentence.getBytes();
        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAdress, 4445);
        clientSocket.close();
    }
}

public class UDPServer {

    public static void main(String[] args) throws IOException {
        DatagramSocket serverSocket = new DatagramSocket(4445);
        byte[] receiveData = new byte[1024];
        while(true) {
            DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
            serverSocket.receive(receivePacket);
            String sentence = new String(receivePacket.getData());
            System.out.println("RECEIVED: " + sentence);
        }
    }
}

Answer 1

You forgot to actually send the package over the socket.

Simply add

clientSocket.send(sendPacket);

just before

clientSocket.close();

in UDPClient.main() and everything will work.