Socket 实现聊天功能

需要提前了解知识点
java.net.Socket 解析
java.net.ServerSocket 解析

使用socket实现一个端对端聊天系统。

消息的格式为：消息长度（int）+消息内容

通过消息长度来进行socket分包，防止读取出现半包、粘包等问题。

服务端代码

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * @author jijs
 * @date 2017-08-14
 */
public class ChatServer {
    public static void main(String[] args) throws Exception {
        start();
    }

    public static void start() throws Exception {
        try (ServerSocket ss = new ServerSocket(9000);
                Socket s = ss.accept();
                InputStream is = s.getInputStream();
                OutputStream os = s.getOutputStream();) {

            //开启一个线程，实时读取对方发过来的消息
            new Thread(ChatUtil.receive(is)).start();

            //从控制台输入消息，并发送
            ChatUtil.send(os);
            
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

客户端代码

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.Socket;

/**
 * @author jijs
 * @date 2017-08-14
 */
public class ChatClient {

    public static void main(String[] args) throws Exception {
        start();
    }

    public static void start() {
        try (Socket s = new Socket("127.0.0.1", 9000);
                InputStream is = s.getInputStream();
                OutputStream os = s.getOutputStream();) {

            //开启一个线程，实时读取对方发过来的消息
            new Thread(ChatUtil.receive(is)).start();

            //从控制台输入消息，并发送
            ChatUtil.send(os);

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

}

聊天工具类

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Scanner;

/**
 * @author jijs
 * @date 2017-08-14
 */
public class ChatUtil {

    /**
     * 读取对方发过来的消息
     * @param is
     * @return
     */
    public static Runnable receive(final InputStream is) {
        return new Runnable() {
            public void run() {
                while (true) {
                    try {
                        // 当前消息总字节长度
                        int returnLen = ChatUtil.readLen(is);
                        byte[] b = new byte[returnLen];
                        int readSize = 0; // 每次读取的字节数
                        int count = 0; // 总读取的字节数
                        while (count < returnLen && (readSize = is.read(b)) != -1) {
                            count += readSize;
                        }
                        String str = new String(b, 0, readSize);
                        System.out.println("接收:" + str);
                    } catch (IOException e) {
                        e.printStackTrace();
                        break;
                    }
                }
            }
        };
    }

    /**
     * 从控制台接收用户输入，发送消息给对方
     * @param os
     */
    public static void send(final OutputStream os) {
        Scanner scan = new Scanner(System.in);
        while (true) {
            try {
                String s = scan.nextLine();
                byte[] data = s.getBytes();
                int len = data.length;
                os.write(ChatUtil.int2byte(len));
                os.write(data);
                os.flush();
            } catch (IOException e) {
                e.printStackTrace();
                break;
            }
        }
        scan.close();
    }
    
    /**
     * 读取消息长度
     * 消息格式为：消息长度+消息内容
     * @param is
     * @return
     * @throws IOException
     */
    public static int readLen(InputStream is) throws IOException {
        int b1 = is.read();
        int b2 = is.read();
        int b3 = is.read();
        int b4 = is.read();
        int len = (b1 << 24) + (b2 << 16) + (b3 << 8) + b4;
        return len;
    }
    
    /**
     * int 转 byte[] 数组
     * @param len
     * @return
     */
    public static byte[] int2byte(int len) {
        byte[] b = new byte[4];
        b[0] = (byte) (len >> 24);
        b[1] = (byte) (len >> 16 & 0XFF);
        b[2] = (byte) (len >> 8 & 0XFF);
        b[3] = (byte) (len & 0XFF);
        return b;
    }
}

客户端控制台：

客户端

服务端控制台：

服务端

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