java實現UDP通訊
阿新 • • 發佈:2020-06-24
1.概述
用DatagramSocket與DatagramPacket實現UDP通訊.UDP比TCP相對來說簡單一點,不需要等待連線,且處理資料不需要用輸出輸出流,只需要DatagramPacket.嚴格來說,UDP沒有服務端和客戶端之分,只有傳送端與接收端之分.
2.傳送端
傳送端首先建立DatagramSocket與DatagramPacket,設定好DatagramPacket的埠與ip,再通過DatagramSocket傳送.
(1)建立DatagramSocket與DatagramPacket
DatagramSocket socket = new DatagramSocket(55555 );
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這裡的55555埠是指資料通過這個埠傳送.
(2)建立DatagramPacket
InetAddress ip = InetAddress.getByName("127.0.0.1");
int port = 12345;
String message = "message";
DatagramPacket packet = new DatagramPacket(message.getBytes(),message.getBytes().length,ip,port);
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構造方法DatagramPacket()的四個引數分別為
- 傳送的位元組陣列
- 位元組陣列長度
- ip
- 埠
這裡埠不能與上面的一致,不然的話會提示埠被佔用.
(3)傳送
socket.send(packet);
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3.接收端
接收端只需指定埠進行接收,這裡的埠在DatagramSocket中的構造方法中指定,與傳送端的傳送的packet中設定的埠一致.
(1)建立DatagramSocket
DatagramSocket socket = new DatagramSocket(12345);
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(2)建立DatagramPacket
這裡建立的DatagramPacket只需要指定儲存資料的位元組陣列與該位元組陣列的長度.
byte [] message = new byte [2048];
DatagramPacket packet = new DatagramPacket(message,message.length);
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(3)接收
socket.receive(packet);
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這個方法會阻塞,直到接收到packet.
(4)獲取資料
接收到packet後可以使用getData()獲取資料,返回位元組陣列,可以傳遞給String的構造方法建立String.
String str = new String(packet.getData());
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4.完整程式碼
這裡人為地設定了客戶端與服務端,可以互相傳送資料,服務端輸入後傳送到服務端,服務端返回固定資料,"客戶端"與"服務端"輪流扮演了傳送端與接收端的角色.配合了swing使用.
(1)Server.java
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import javax.swing.*;
public class Server
{
public static void main(String[] args)
{
JFrame frame = new JFrame("Server");
JTextArea text = new JTextArea();
frame.add(text);
frame.setSize(600,300);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
try
{
byte [] message = new byte[2048];
DatagramSocket socket = new DatagramSocket(12345);
DatagramPacket packet = new DatagramPacket(message,message.length);
socket.receive(packet);
InetAddress ip = packet.getAddress();
int port = packet.getPort();
text.setText("ip : "+ip.toString()+"\n");
text.append("port : "+port+"\n");
text.append("message : "+new String(packet.getData()));
String messageFromServer = "Message from server";
packet = new DatagramPacket(messageFromServer.getBytes(),messageFromServer.getBytes().length,port);
socket.send(packet);
socket.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
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(2)Client.java
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.Socket;
import javax.swing.*;
import java.awt.GridLayout;
public class Client
{
public static void main(String[] args) {
JFrame frame = new JFrame();
JTextArea text = new JTextArea();
JButton send = new JButton("send");
GridLayout layout = new GridLayout(2,1,1);
frame.setLayout(layout);
frame.setTitle("Client");
frame.setVisible(true);
frame.setLocationRelativeTo(null);
frame.setSize(600,300);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.add(text);
frame.add(send);
send.addActionListener( v->
{
try
{
InetAddress ip = InetAddress.getByName("127.0.0.1");
int port = 12345;
DatagramSocket socket = new DatagramSocket(55555);
String message = text.getText();
DatagramPacket packet = new DatagramPacket(message.getBytes(),port);
socket.send(packet);
byte [] messageFromServer = new byte[2048];
packet = new DatagramPacket(messageFromServer,messageFromServer.length);
socket.receive(packet);
text.setText(new String(packet.getData()));
socket.close();
}
catch (IOException e)
{
e.printStackTrace();
}
});
}
}
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