UDP是一种面向无连接的协议,因此传输过程中不能保证数据的完整性。jdk提供了网络通信包,在java.net包下提供了两个类DatagramPacket和DatagramSocket来实现UDP通信。这两个类可以这样理解,DatagramSocket是路,DatagramPacket路上装有人的车。也就是DatagramSocket决定了通信目标,DatagramPacket则代表封装好的数据。
UDP的特性决定了UDP协议的应用场景,在我身边最常见的应用场景就是物联网设备与服务端的通信。
public class UDPClient {
public static void main(String[] args) throws Exception {
byte[] data = "我是客户端,我发送了一条消息".getBytes();
InetAddress address = InetAddress.getByName("localhost");
DatagramPacket packet = new DatagramPacket(data,data.length,address,8888);
DatagramSocket socket = new DatagramSocket();
socket.send(packet);
byte[] message = new byte[1024];
DatagramPacket packet1 = new DatagramPacket(message,message.length);
socket.receive(packet1);
String replyContent = new String(message,0,message.length);
System.out.println("UDPClient 接收到了消息:"+replyContent);
socket.close();
}
}
public class UDPServer {
public static void main(String[] args) throws Exception {
DatagramSocket socket = new DatagramSocket(8888);
byte[] data = new byte[1024];
DatagramPacket packet = new DatagramPacket(data,data.length);
socket.receive(packet);
String message = new String(data,0,packet.getLength());
System.out.println("UDPServer 接收到了消息:"+message);
InetAddress address = packet.getAddress();
int port = packet.getPort();
byte[] replyContent = "我是服务端,我回复了一条消息".getBytes();
DatagramPacket packet1 = new DatagramPacket(replyContent, replyContent.length, address, port);
socket.send(packet1);
socket.close();
}
}
TCP是一种面向连接的服务,经过三次握手建立连接,通过传输字节流的方式进行通信。因此可以保证消息的完整性。同样,在java.net包下也提供了两个包Socket和ServerSocket来实现TCP通信。
public class TCPClient {
public static void main(String[] args) throws Exception {
Socket socket = new Socket("localhost",8081);
DataOutputStream out = new DataOutputStream(socket.getOutputStream());
String data = "我是客户端,我发了一条消息";
out.writeUTF(data);
DataInputStream in = new DataInputStream(socket.getInputStream());
String message = in.readUTF();
System.out.println("TCPClient:"+message);
socket.close();
}
}
public class TCPServer {
public static void main(String[] args) throws Exception{
ServerSocket serverSocket = new ServerSocket(8081);
Socket socket = serverSocket.accept();
DataInputStream in = new DataInputStream(socket.getInputStream());
String message = in.readUTF();
System.out.println("TCPServer:"+message);
DataOutputStream out = new DataOutputStream(socket.getOutputStream());
out.writeUTF("我是服务器,我回复了一条消息");
socket.close();
serverSocket.close();
}
}