java Tcp protocol socket programming learning

The main steps I learned

The first step: Create a new socket object with a specific port (such as 4800)
The second step: Construct a BufferedReader object with the system input device, which is used to receive characters input by the system keyboard
The third step : Use the socket object to get the output stream to construct the PrintWriter
Step 4: Use the socket object to get the input stream to construct the corresponding BufferedReader object. This object is used to receive the information sent from the server.

Close the socket as I understand it: open it first is closed later, and the socket is closed last.

The following is the client code implementation:

package com.fan.socket;

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

public class SocketClient {
public static void main(String[] args) throws IOException{

try{
Socket socket=new Socket("127.0.0.1",4800);
System.out.println("client start...");
//To the 4800 port of this machine Issue a customer request
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
//Construct a BufferedReader object from the system standard input device
PrintWriter write=new PrintWriter(socket.getOutputStream());
//Constructed from the Socket object Get the output stream and construct the PrintWriter object
BufferedReader in=new BufferedReader(new InputStreamReader(socket.getInputStream()));
//Get the input stream from the Socket object and construct the corresponding BufferedReader object
String readline;
readline=br .readLine(); //Read a string from the system standard input
while(!readline.equals("end")){
//If the string read from the standard input is "end", stop the loop
write.println(readline);
//Output the string read from the system standard input to Server2
write.flush();
//Refresh the output stream so that the Server receives the string immediately
System.out. println("Client:"+readline);
//Print the read string on the system standard output
System.out.println("Server:"+in.readLine());
//Read from Server A string and print it to the standard output
readline=br.readLine(); //Read a string from the system standard input
} //Continue the loop
write.close(); //Close the Socket output stream
in.close(); //Close the Socket input stream
socket.close(); //Close the Socket
}catch(Exception e) {
System.out.println("can not listen to:"+e);/ /Error, print error message
}
}

}

Server code implementation:

package com.fan.socket;

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

public class SocketService {
public static void main(String[] args) throws IOException{
SocketService socketService = new SocketService();
socketService.oneServer();
}

public void oneServer(){
try{
ServerSocket server=null;
try{
server=new ServerSocket(4800);
System.out.println("server start is ok...");
// Create a ServerSocket to listen to customer requests on port 4800
}catch(Exception e) {
System.out.println("can not listen to:"+e);
//Error, print error message
}
Socket socket=null ;
try{
socket=server.accept();
//Use accept() to block and wait for customer requests. When a customer
//request arrives, a Socket object is generated and continues to execute
}catch(Exception e) {
System.out.println("Error."+e);
//Error, print error message
}
String line;
BufferedReader in=new BufferedReader(new InputStreamReader(socket.getInputStream()));
//By The Socket object gets the input stream and constructs the corresponding BufferedReader object
PrintWriter writer=new PrintWriter(socket.getOutputStream());
//Gets the output stream from the Socket object and constructs the PrintWriter object
BufferedReader br=new BufferedReader(new InputStreamReader( System.in));
//Construct a BufferedReader object from the system standard input device
System.out.println("Client:"+in.readLine());
//Print the content read from the client on the standard output String
line=br.readLine();
//Read a string from standard input
while(!line.equals("end")){
//Stop if the string is "end" Loop
writer.println(line);
//Output the string to the client
writer.flush();
//Refresh the output stream so that the client can receive the string immediately
System.out.println("Server :"+line);
//Print the read string on the system standard output
System.out.println("Client:"+in.readLine());
//Read a string from the Client, And print to the standard output
line=br.readLine();
//Read a string from the system standard input
} //Continue the loop
writer.close(); //Close the Socket output stream
in.close (); //Close the Socket input stream
socket.close(); //Close the Socket
server.close(); //Close the ServerSocket
}catch(Exception e) {//Error, print error message
System.out .println("Error."+e);
}
}
}