Detailed explanation of Java network programming examples

1. Socket

The network driver provides an interface and a mechanism for application programming. It can be likened to a port terminal application that only needs to put the goods here. , even if the delivery of the goods is completed. It is created in the application, establishes a relationship with the driver through a binding mechanism, and tells itself the corresponding IP and Port.

Socket is a network programming class in java, located in the java.net package.

---- DatagramSocket //Used for UDP communication

---- ServerSocket //Used for TCP communication, used for server side

---- Socket //Server and client used for Tcp communication

2. UDP network program

InetAddress class represents the Internet Protocol (IP) address

//static InetAddress getLocalHost() throws UnknownHostException Returns the local host

//static InetAddress getByName(String host) Determines the IP address of the host given the host name. The hostname can be the machine name
 

##//static InetAddress[] getAllByName(String host) according to Hostname returns an array of its IP address.

static void ipDemo() throws UnknownHostException{
                InetAddress netAddr=InetAddress.getLocalHost();                //取得本地电脑的一些信息System.out.println(netAddr.toString());  
                System.out.println(netAddr.getHostAddress());
                System.out.println(netAddr.getHostName()); //取得其他电脑的信息InetAddress netAddr2=InetAddress.getByName("DELL-PC");  //这里也可以传IP地址System.out.println(netAddr2.getHostAddress());  //169.254.170.71System.out.println(netAddr2.getHostName()); //DELL-PC                //取得百度的地址InetAddress []  ipList=InetAddress.getAllByName("www.baidu.com");for(InetAddress addr:ipList){
                    System.out.println(addr.toString()); 
                }
            }

3. UDP sending and receiving DatagramSocket, DatagramPacket

//Example 1 The simplest sending and receiving

The sending end == needs to import the java.net package

Send the data through UDP:

1) Establish a UDPSocket service

2) Provide data and encapsulate the data into the data packet DatagramPacket (byte[] buf, int length, InetAddress address, int port) //There are multiple constructors

3) Send data through the Socket service

4) Close Resource

import java.net.*;class Sender4{//DatagramPacket (byte[] buf, int length, InetAddress address, int port) public static void main(String [] args) throws Exception
                                {                                      byte [] buff="hello cat".getBytes(); 
                                        DatagramSocket socket=new DatagramSocket();
                                        DatagramPacket packet=new DatagramPacket(buff,buff.length,InetAddress.getByName("192.168.0.103"),8888);
                                        socket.send(packet);
                                        socket.close();
                                        System.out.println("ok");
                                }
                            }

--Receiver

1) Create a Socket service and specify to listen on a certain port

2) Create a receiving Data DatagramPacket

3) Take out the data from the package

4) Close the resource

import java.net.*;class Receive4
                            {public static void main(String [] args) throws Exception
                                {
                                DatagramSocket socket=new DatagramSocket(8888); //别忘了端口号byte[] buff=new byte[1024] ;
                                    DatagramPacket packet=new DatagramPacket(buff,buff.length);
                                    
                                    socket.receive(packet);
                                    
                                    String senderIp=packet.getAddress().getHostAddress();
                                    String senderData=new String(packet.getData(),0,packet.getLength());int senderPort=packet.getPort();
                                    System.out.println(senderIp+"---"+senderData+"---"+senderPort);
                                    
                                    socket.close();
                                }
                            }

// Example 2, cyclic sending and receiving

import java.net.*;import java.io.*;class NewSender{public static void main(String [] args) throws Exception
                        {
                                System.out.println("发送端启动了");
                                DatagramSocket socket=new DatagramSocket();
                                
                                BufferedReader br=new BufferedReader(new InputStreamReader(System.in)); //包装键盘输入流String str=null;while((str=br.readLine())!=null){byte [] buff=str.getBytes();
                                        DatagramPacket packet=new DatagramPacket(buff,buff.length,InetAddress.getByName("127.0.0.1"),9000);
                                        socket.send(packet);
                                }
                                
                                br.close();
                                socket.close();            
                        }    
                    }

import java.net.*;class NewReceiver{public static void main(String [] args) throws Exception
                    {
                            DatagramSocket socket=new DatagramSocket(9000);
                            System.out.println("接收端启动了");                            while(true){ 
                                  byte [] buff=new byte[1024] ; 
                                  DatagramPacket packet=new DatagramPacket(buff,buff.length);
                                  socket.receive(packet);
                                  
                                  String senderIp=packet.getAddress().getHostAddress();                                  int sendPort=packet.getPort();
                                  String msg= new String(packet.getData(),0,packet.getLength());
                                  
                                  System.out.println(senderIp+":"+sendPort+":"+msg);    
                            }
                    }
                }

## Example 3: Multi-threaded chat room program

class Chat
        {public static void main(String [] args)
                {new Thread(new SendThread()).start(); new Thread(new ReceiveThread()).start(); 
                }
        }

//发送端import java.io.*;import java.net.*;class SendThread implements Runnable
        {              private DatagramSocket socket;public void run()
                {try{
                        socket=new DatagramSocket();
                        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
                        String msg=null;while((msg=br.readLine())!=null){byte[] buff=msg.getBytes();
                            DatagramPacket packet=new DatagramPacket(buff,buff.length,InetAddress.getByName("127.0.0.1"),10000);
                            socket.send(packet);
                        }
                        
                        socket.close();
                        br.close();
                    }catch(Exception ex){
                        ex.printStackTrace();
                    }
                }
        }

//接收端import java.net.*;class ReceiveThread implements Runnable{    private DatagramSocket socket;                    public void run(){try{
                        socket=new DatagramSocket(10000);while(true){byte [] buff=new byte[1024];
                            DatagramPacket packet=new DatagramPacket(buff,buff.length);
                            socket.receive(packet);
                            
                            String senderIp=packet.getAddress().getHostAddress();int senderPort=packet.getPort();
                            String msg=new String(packet.getData(),0,packet.getLength());
                            
                            System.out.println(senderIp+":"+senderPort+":"+msg);
        
                        }
                    }catch(Exception ex)
                    {
                        System.out.println(ex.getMessage());
                    }
                }    
        }

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