Java案例：基于TCP的简单聊天程序

一、如何实现TCP通信

• 要实现TCP通信需要创建一个服务器端程序和一个客户端程序，为了保证数据传输的安全性，首先需要实现服务器端程序，然后在编写客户端程序。
• 在本机运行服务器端程序，在远程机运行客户端程序
• 本机的IP地址：192.168.129.222
  
• 远程机的IP地址：192.168.214.213
  

二、编写C/S架构聊天程序

（一）编写服务器端程序 - Server.java

• 在net.hw.network包里创建Server类
  

package net.hw.network;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * 功能：服务器端
 * 作者：华卫
 * 日期：2022年03月18日
 */
public class Server extends JFrame {
    static final int PORT = 8136;
    static final String HOST_IP = "192.168.129.222";

    private JPanel panel1, panel2;
    private JTextArea txtContent, txtInput, txtInputIP;
    private JScrollPane panContent, panInput;
    private JButton btnClose, btnSend;

    private ServerSocket serverSocket;
    private Socket socket;
    private DataInputStream netIn;
    private DataOutputStream netOut;

    public static void main(String[] args) {
        new Server();
    }

    public Server() {
        super("服务器");

        //创建组件
        panel1 = new JPanel();
        panel2 = new JPanel();
        txtContent = new JTextArea(15, 60);
        txtInput = new JTextArea(3, 60);
        panContent = new JScrollPane(txtContent, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        panInput = new JScrollPane(txtInput, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        btnClose = new JButton("关闭");
        btnSend = new JButton("发送");

        //添加组件
        getContentPane().add(panContent, "Center");
        getContentPane().add(panel1, "South");
        panel1.setLayout(new GridLayout(0, 1));
        panel1.add(panInput);
        panel1.add(panel2);
        panel2.add(btnSend);
        panel2.add(btnClose);

        //设置组件属性
        txtContent.setEditable(false);
        txtContent.setFont(new Font("宋体", Font.PLAIN, 13));
        txtInput.setFont(new Font("宋体", Font.PLAIN, 15));
        txtContent.setLineWrap(true);
        txtInput.setLineWrap(true);
        txtInput.requestFocus();
        setSize(450, 350);
        setLocation(50, 200);
        setResizable(false);
        setVisible(true);

        //等候客户请求	
        try {
            txtContent.append("服务器已启动...\n");
            serverSocket = new ServerSocket(PORT);
            txtContent.append("等待客户请求...\n");
            socket = serverSocket.accept();
            txtContent.append("连接一个客户。\n" + socket + "\n");
            netIn = new DataInputStream(socket.getInputStream());
            netOut = new DataOutputStream(socket.getOutputStream());
        } catch (IOException e1) {
            e1.printStackTrace();
        }

        /

        //注册监听器，编写事件代码	
        txtContent.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseMoved(MouseEvent e) {
                displayClientMsg();
            }
        });

        txtInput.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseMoved(MouseEvent e) {
                displayClientMsg();
            }
        });

        panel2.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseMoved(MouseEvent e) {
                displayClientMsg();
            }
        });

        txtInput.addKeyListener(new KeyAdapter() {
            public void keyTyped(KeyEvent e) {
                displayClientMsg();
            }
        });

        txtInput.addFocusListener(new FocusAdapter() {
            public void focusGained(FocusEvent e) {
                displayClientMsg();
            }
        });

        btnSend.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {

                    String serverMsg = txtInput.getText();
                    if (!serverMsg.trim().equals("")) {
                        txtContent.append("服务器>" + serverMsg + "\n");
                        netOut.writeUTF(serverMsg);
                    } else {
                        JOptionPane.showMessageDialog(null, "不能发送空信息！", "服务器", JOptionPane.WARNING_MESSAGE);
                    }

                    txtInput.setText("");
                    txtInput.requestFocus();
                } catch (IOException ie) {
                    ie.printStackTrace();
                }
            }
        });

        btnClose.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                try {
                    netIn.close();
                    netOut.close();
                    socket.close();
                    serverSocket.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                System.exit(0);
            }
        });

        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                try {
                    netIn.close();
                    netOut.close();
                    socket.close();
                    serverSocket.close();
                } catch (IOException ie) {
                    ie.printStackTrace();
                }
                System.exit(0);
            }

            public void windowActivated(WindowEvent e) {
                txtInput.requestFocus();
            }
        });
    }

    //显示客户端信息
    void displayClientMsg() {
        try {
            if (netIn.available() > 0) {
                String clientMsg = netIn.readUTF();
                txtContent.append("客户端>" + clientMsg + "\n");
            }
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }
}

（二）编写客户端程序 - Client.java

• 在net.hw.network包里创建Client类
  

package net.hw.network;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.InetAddress;
import java.net.Socket;

/**
 * 功能：客户端
 * 作者：华卫
 * 日期：2022年03月18日
 */
public class Client extends JFrame {

    private JPanel panel1, panel2;
    private JTextArea txtContent, txtInput;
    private JScrollPane panContent, panInput;
    private JButton btnClose, btnSend;

    private Socket socket;
    private DataInputStream netIn;
    private DataOutputStream netOut;

    public static void main(String[] args) {
        new Client();
    }

    public Client() {
        super("客户端");

        //创建组件
        panel1 = new JPanel();
        panel2 = new JPanel();
        txtContent = new JTextArea(15, 60);
        txtInput = new JTextArea(3, 60);
        panContent = new JScrollPane(txtContent, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        panInput = new JScrollPane(txtInput, ScrollPaneConstants.VERTICAL_SCROLLBAR_AS_NEEDED, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
        btnClose = new JButton("关闭");
        btnSend = new JButton("发送");

        //添加组件
        getContentPane().add(panContent, "Center");
        getContentPane().add(panel1, "South");
        panel1.setLayout(new GridLayout(0, 1));
        panel1.add(panInput);
        panel1.add(panel2);
        panel2.add(btnSend);
        panel2.add(btnClose);

        //设置组件属性
        txtContent.setEditable(false);
        txtContent.setFont(new Font("宋体", Font.PLAIN, 13));
        txtInput.setFont(new Font("宋体", Font.PLAIN, 15));
        txtContent.setLineWrap(true);
        txtInput.setLineWrap(true);
        txtInput.requestFocus();
        setSize(450, 350);
        setLocation(550, 200);
        setResizable(false);
        setVisible(true);

        //连接服务器
        try {
            txtContent.append("连接服务器...\n");
            socket = new Socket(Server.HOST_IP, Server.PORT);
            txtContent.append("连接服务器成功。\n" + socket + "\n");
            netIn = new DataInputStream(socket.getInputStream());
            netOut = new DataOutputStream(socket.getOutputStream());
        } catch (IOException e1) {
            JOptionPane.showMessageDialog(null, "服务器连接失败！\n请先启动服务器程序！", "客户端", JOptionPane.ERROR_MESSAGE);
            System.exit(1);
        }

        /

        //注册监听器，编写事件代码
        txtContent.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseMoved(MouseEvent e) {
                displayServerMsg();
            }
        });

        txtInput.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseMoved(MouseEvent e) {
                displayServerMsg();
            }
        });

        panel2.addMouseMotionListener(new MouseMotionAdapter() {
            public void mouseMoved(MouseEvent e) {
                displayServerMsg();
            }
        });

        txtInput.addKeyListener(new KeyAdapter() {
            public void keyTyped(KeyEvent e) {
                displayServerMsg();
            }
        });

        txtInput.addFocusListener(new FocusAdapter() {
            public void focusGained(FocusEvent e) {
                displayServerMsg();
            }
        });

        btnSend.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {

                    String clientMsg = txtInput.getText();
                    if (!clientMsg.trim().equals("")) {
                        netOut.writeUTF(clientMsg);
                        txtContent.append("客户端>" + clientMsg + "\n");
                    } else {
                        JOptionPane.showMessageDialog(null, "不能发送空信息！", "客户端", JOptionPane.WARNING_MESSAGE);
                    }

                    txtInput.setText("");
                    txtInput.requestFocus();
                } catch (IOException ie) {
                    ie.printStackTrace();
                }
            }
        });

        btnClose.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                try {
                    netIn.close();
                    netOut.close();
                    socket.close();
                } catch (IOException ie) {
                    ie.printStackTrace();
                }
                System.exit(0);
            }
        });

        addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                try {
                    netIn.close();
                    netOut.close();
                    socket.close();
                } catch (IOException ie) {
                    ie.printStackTrace();
                }
                System.exit(0);
            }

            public void windowActivated(WindowEvent e) {
                txtInput.requestFocus();
            }
        });
    }

    //显示服务端信息
    void displayServerMsg() {
        try {
            if (netIn.available() > 0) {
                String serverMsg = netIn.readUTF();
                txtContent.append("服务器>" + serverMsg + "\n");
            }
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }
}

（三）测试服务器端与客户端能否通信

• 在本机[192.168.129.222]上启动服务器端
  
• 在远程机[192.168.214.213]上启动客户端
  
• 显示连接服务器[192.168.129.222]成功，切换到服务器端查看,显示连接了一个客户[192.168.214.213]
  
• 此时，服务器端和客户端就可以相互通信了
  

（四）程序优化思路 - 服务器端采用多线程

• 其实，很多服务器端程序都是允许被多个应用程序访问的，例如门户网站可以被多个用户同时访问，因此服务器端都是多线程的。