Introduction to socket UDP and TCP

Socket UDP、TCP brief introduction

1.1 Java obtain IP、URL

// obtain IP
public class IPDemo {
    
	public static void main(String[] args) throws UnknownHostException {
    
		// Access to the local IP： Host name  / 127.0.0.1 / localhost
		InetAddress ip=InetAddress.getByName("gudu");
		System.out.println(ip);
		System.out.println(ip.getHostAddress()); // return IP
		System.out.println(ip.getHostName());    // Return computer name 
		System.out.println(ip.getLocalHost());     // Get the local host IP
		
		System.out.println("----------------------- Get network IP------------------------");
		
		InetAddress baiduIP=InetAddress.getByName("www.baidu.com");
		System.out.println(baiduIP);
	}

}
// obtain url
public class URLDemo {
    
	public static void main(String[] args){
    
		InputStream in=null;
		OutputStream out=null;
		// Given a URL Address 
		try {
    
			URL url=new URL("");
			// Establish a channel 
			URLConnection conn=url.openConnection();
			// adopt URLConnection Object get object stream 
			 in=conn.getInputStream();
			File file =new File("D:URL");
			if(!file.exists()){
    
				file.mkdirs();// Create folder 
			}
			out=new FileOutputStream(file.getPath()+"/"+"pag.png");
			byte[] buf=new byte[1024];
			int len =-1;
			System.out.println(" Download start ........");
			while(-1!=(len=in.read(buf))){
    
				out.write(buf, 0, len);
			}
			System.out.println(" Download successful ........");
		} catch (MalformedURLException e) {
    
			e.printStackTrace();
		} catch (IOException e) {
    
			e.printStackTrace();
		}finally {
    
			try {
    
				out.close();
			} catch (IOException e) {
    
				e.printStackTrace();
			}
			try {
    
				in.close();
			} catch (IOException e) {
    
				e.printStackTrace();
			}
		}
	}

}

1.2 UDP Server side \ client

// establish UDP The receiving end of 
public class ReceiveDemo {
    
	public static void main(String[] args) throws IOException {
    
		
        //1. establish UDP Socket  Receiver object （DatagramSocket）, Because you want to receive the database , So specify a port 
		DatagramSocket ds =new  DatagramSocket(10003);
		System.out.println(" Receiver start .........");
		
		//2. Create datagram packet object  ( DatagramPacket )
		byte[] buf=new byte[1024];
		DatagramPacket dp=new DatagramPacket(buf, buf.length);
		
		//3. Use  receive()  Method accepts datagram packets 
		ds.receive(dp);// Blocking 
		
		//4. Get information through the method of datagram package object 
		byte[] data=dp.getData();                  // Get the data sent 
		InetAddress ip=dp.getAddress();      // Get the IP
		int port=dp.getPort();                       // Get the port number of the sender 
		System.out.println(ip+" Said the "+new String(data,0,dp.getLength()));
		ds.close();                                          // Closed flow 
	}
}

/** *  Byte array  +Data  Input stream  * @param data * @return * @throws IOException */
public static double convert(byte[] data) throws IOException{
    
	DataInputStream dis =new DataInputStream(new ByteArrayInputStream(data));
	double num =dis.readDouble();  // The next eight bytes of this input stream , Interpret them as a  double
	dis.close();
	return num;
}

// establish UDP The sender of 
public class SendDemo {
    
	public static void main(String[] args) throws IOException {
    
		
		//1. establish UDP Of DatagramSocket object , Indicate the external port number 
		DatagramSocket ds=new DatagramSocket(10002);
		System.out.println(" Sender start ........");
		
		//2. adopt DatagramPacket Object to package 
		byte[] buf=" test , I love you! ".getBytes();
		DatagramPacket dp=new DatagramPacket(buf, buf.length,
				InetAddress.getByName("127.0.0.1"),10003);
		
		//3. adopt  DatagramSocket Of  send() , Send the datagram packet to the specified receiving end 
		ds.send(dp);
		
		ds.close();
	}
}

/** *  Byte array   data source  +Data  Output stream  * @param num * @return * @throws IOException */
public static byte[] convert(double num) throws IOException{
    
	byte[] data =null;
	ByteArrayOutputStream bos = new ByteArrayOutputStream();
	DataOutputStream dos =new DataOutputStream(bos);
	dos.writeDouble(num);      //  Will a  double  Value is written to the output stream 
	
	  dos.flush();
	// get data 
	data = bos.toByteArray();  
	//  Create a new assigned  byte  Array whose size is the current size of this output stream , And the valid contents of the buffer have been copied to the array . 
	
	dos.close();		
	return data;
	
  }
}

1.3 TCP Server side / client

//TCP Protocol transfer  ：  Establishment of server side 
/** step  * 1. establish TCP Server side objects （ServerSocket） * 2. call accept() Method to get the... Of the client brought by the connection Socket object  * 3. Through the client Scoket Object acquisition IO Stream to read data  * 4. */
public class ServerDemo {
    
	public static void main(String[] args) throws IOException {
    
		ServerSocket server=new ServerSocket(10001);
		Socket client=null;
		InputStream in=null;
		System.out.println(" Server startup ........");
		boolean b=true;
		while(b){
    
			client=server.accept( );          // Listen and accept connections to this socket 
			in=client.getInputStream();    // Returns the input stream for this socket .
			byte[] buf=new byte[1024];
			int len=in.read(buf);
			InetAddress ip=client.getInetAddress();
			System.out.println(ip+" say "+new String(buf,0,len));
		}
		server.close();
		client.close();
	}

}

//TCP Protocol transfer  ：  The establishment of the client 
/** step  * 1. establish TCP Client object （Socket） * 2. If the connection to the server is successful , adopt Socket Object acquisition IO flow  * 3. Use IO flow , Data operation  * 4. close resource  */
public class ClientDemo {
    
	public static void main(String[] args) throws  IOException {
    
		Socket client=new Socket("127.0.0.1",10001);
		
		OutputStream out=client.getOutputStream();
		
		out.write(" Hello Server".getBytes());
		
		client.close();
	}

}