Intermediate Java(45) - How to Send Messages

import java.io.*;

import java.net.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class Server extends JFrame {

private JTextField userText;

private JTextArea chatwindow;

private ObjectOutputStream output;

private ObjectInputStream input;

private ServerSocket server;

private Socket connection;

//constructor

public Server(){

super("My Awesome Instant Messenger");

userText = new JTextField();

userText.setEditable(false);

userText.addActionListener(

new ActionListener(){

public void actionPerformed(ActionEvent event){

sendMessage(event.getActionCommand());

userText.setText("");

}

}

);

add(userText,BorderLayout.NORTH);

chatwindow = new JTextArea();

add(new JScrollPane(chatwindow));

setSize(400,200);

setVisible(true);

}

//設置和運行server

public void startRunning(){

try{

server = new ServerSocket(6789,10); → 服務器端口(port)和多少人可以等待

while(true){

try{

//連接並有談話

waitForConnection(); → 等待有人連接服務器的函數

setupStreams(); → 設置Stream可以接收和發送的函數

whileChatting(); → 聊天時做什麼的函數

}catch(EOFException eofException){ → 當連接結束例外處理

showMessage("\n Server ended the connection");

}finally{

closeCrap();

}

}

}catch(IOException ioException){

ioException.printStackTrace();

}

}

//等待連接，然後顯示連接信息

private void waitForConnection() throws IOException{

showMessage("Waiting for someone connect....\n");

connection = server.accept(); → 當有人嘗試連接server，接受連接

showMessage("Now connected to "+connection.getInetAddress().getHostName());

}

//獲得Stream發送和接收數據

private void setupStreams() throws IOException{

output = new ObjectOutputStream(connection.getOutputStream());

output.flush(); → 當完成發送的動作，然後刷新

input = new ObjectInputStream(connection.getInputStream());

showMessage("\n Stream are now setup! \n");

}

//當聊天對話

private void whileChatting() throws IOException{

String message = "You are now connected!";

sendMessage(message);

ableToType(true);

do{

//有一個對話

try{

message = (String)input.readObject(); → 服務器收到什麼改為String

showMessage("\n"+ message); → 隔行顯示

}catch(ClassNotFoundException classNotFoundException){ → 如果用戶發送無法識別

showMessage("\n Oh my God! what you sent");

}

}while(!message.equals("CLIENT – END")); → 當客戶端打END,不連接Server

}

//完成聊天後關閉Stream和connection

private void closeCrap(){

showMessage("\n Closing connections... \n");

ableToType(false);

try{

output.close();

input.close();

connection.close();

}catch(IOExcetion ioException){

ioException.printStackTrace();

}

}

//發送消息到客戶端

private void sendMessage(String message){

try{

output.writeObject("SERVER - "+message); → 將這個對象寫入到input

output.flush(); → 刷新和清除內存

showMessage("\nSERVER - " + message);

}catch(IOException ioException){ → 如果發送消息有錯誤

chatwindow.append("\n ERROR:I CAN'T SEND THAT MESSAGE"); → 在chatwindow顯示消息

}

}

}