InetAddress address = null;
    try {
      address = InetAddress.getByName("192.168.50.182");//某个确定的主机地址
    } catch (UnknownHostException e) {
      e.printStackTrace();
    }

    //public String getHostName():获取此IP地址的主机名
    String name = address.getHostName();
    //public String getHostAddress():返回文本显示中的IP地址字符串
    String ip = address.getHostAddress();

//send
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

/*
    UDP发送数据:
        数据来自于键盘录入,直到输入的数据是886,发送数据结束
 */
public class SendDemo {
  public static void main(String[] args) throws IOException {
    //创建发送端的Socket对象(DatagramSocket)
    DatagramSocket ds = new DatagramSocket();
    //自己封装键盘录入数据
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String line;
    while ((line = br.readLine()) != null) {
      //输入的数据是886,发送数据结束
      if ("886".equals(line)) {
        break;
      }
      //创建数据,并把数据打包
      byte[] bys = line.getBytes();
      DatagramPacket dp = new DatagramPacket(bys, bys.length, InetAddress.getByName("192.168.50.182"), 12345);

      //调用DatagramSocket对象的方法发送数据
      ds.send(dp);
    }
    //关闭发送端
    ds.close();
  }
}
  
//receive
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;

/*
    UDP接收数据:
        因为接收端不知道发送端什么时候停止发送,故采用死循环接收
 */
public class ReceiveDemo {
  public static void main(String[] args) throws IOException {
    //创建接收端的Socket对象(DatagramSocket)
    DatagramSocket ds = new DatagramSocket(12345);
    while (true) {
      //创建一个数据包,用于接收数据
      byte[] bys = new byte[1024];
      DatagramPacket dp = new DatagramPacket(bys, bys.length);
      //调用DatagramSocket对象的方法接收数据
      ds.receive(dp);
      //解析数据包,并把数据在控制台显示
      System.out.println("数据是:" + new String(dp.getData(), 0, dp.getLength()));
    }
    //关闭接收端
    //        ds.close();
  }
}

import java.io.*;
import java.net.Socket;

public class ClientDemo {
  public static void main(String[] args) throws IOException {
    Socket s = new Socket("127.0.0.1", 10000);
    BufferedReader br = new BufferedReader(new FileReader("./in.txt"));
    BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));

    String line;
    while ((line = br.readLine()) != null) {
      bw.write(line);
      bw.newLine();
      bw.flush();
    }
    s.shutdownOutput();

    BufferedReader brClient = new BufferedReader(new InputStreamReader(s.getInputStream()));
    String data = brClient.readLine();
    System.out.println("服务器回复:" + data);
    br.close();
    s.close();
  }
}

//---

import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;

public class ServerDemo {
  public static void main(String[] args) throws IOException {
    ServerSocket ss = new ServerSocket(10000);
    while (true) {
      Socket s = ss.accept();
      new Thread(new ServerThread(s)).start();
    }
  }

  static class ServerThread implements Runnable {
    private Socket s;

    public ServerThread(Socket s) {
      this.s = s;
    }

    @Override
    public void run() {
      try {
        BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
        int count = 0;
        File f = new File("Copy" + count + ".java");
        while (f.exists()) {
          count++;
          f = new File("Copy" + count + ".java");
        }
        BufferedWriter bw = new BufferedWriter(new FileWriter(f));
        String line;
        while ((line = br.readLine()) != null) {
          bw.write(line);
          bw.newLine();
          bw.flush();
        }
        BufferedWriter bwServer = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
        bwServer.write("文件上传成功");
        bwServer.newLine();
        bwServer.flush();

        s.close();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
  }

}