作者：jijs
链接：http://www.jianshu.com/p/7c0722a8b66f
來源：简书
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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
1 import java.io.IOException;
2 import java.io.InputStream;
3 import java.io.OutputStream;
4 import java.net.ServerSocket;
5 import java.net.Socket;
6
7 /**
8 * @author jijs
9 * @date 2017-08-14
10 */
11 public class ChatServer {
12 public static void main(String[] args) throws Exception {
13 start();
14 }
15
16 public static void start() throws Exception {
17 try (ServerSocket ss = new ServerSocket(9000);
18 Socket s = ss.accept();
19 InputStream is = s.getInputStream();
20 OutputStream os = s.getOutputStream();) {
21
22 //开启一个线程，实时读取对方发过来的消息
23 new Thread(ChatUtil.receive(is)).start();
24
25 //从控制台输入消息，并发送
26 ChatUtil.send(os);
27
28 } catch (IOException e) {
29 e.printStackTrace();
30 }
31
32 }
33
34 }
客户端代码
1 import java.io.IOException;
2 import java.io.InputStream;
3 import java.io.OutputStream;
4 import java.net.Socket;
5
6 /**
7 * @author jijs
8 * @date 2017-08-14
9 */
10 public class ChatClient {
11
12 public static void main(String[] args) throws Exception {
13 start();
14 }
15
16 public static void start() {
17 try (Socket s = new Socket("127.0.0.1", 9000);
18 InputStream is = s.getInputStream();
19 OutputStream os = s.getOutputStream();) {
20
21 //开启一个线程，实时读取对方发过来的消息
22 new Thread(ChatUtil.receive(is)).start();
23
24 //从控制台输入消息，并发送
25 ChatUtil.send(os);
26
27 } catch (IOException e) {
28 e.printStackTrace();
29 }
30
31 }
32
33 }
聊天工具类
1 import java.io.IOException;
2 import java.io.InputStream;
3 import java.io.OutputStream;
4 import java.util.Scanner;
5
6 /**
7 * @author jijs
8 * @date 2017-08-14
9 */
10 public class ChatUtil {
11
12 /**
13 * 读取对方发过来的消息
14 * @param is
15 * @return
16 */
17 public static Runnable receive(final InputStream is) {
18 return new Runnable() {
19 public void run() {
20 while (true) {
21 try {
22 // 当前消息总字节长度
23 int returnLen = ChatUtil.readLen(is);
24 byte[] b = new byte[returnLen];
25 int readSize = 0; // 每次读取的字节数
26 int count = 0; // 总读取的字节数
27 while (count < returnLen && (readSize = is.read(b)) != -1) {
28 count += readSize;
29 }
30 String str = new String(b, 0, readSize);
31 System.out.println("接收:" + str);
32 } catch (IOException e) {
33 e.printStackTrace();
34 break;
35 }
36 }
37 }
38 };
39 }
40
41 /**
42 * 从控制台接收用户输入，发送消息给对方
43 * @param os
44 */
45 public static void send(final OutputStream os) {
46 Scanner scan = new Scanner(System.in);
47 while (true) {
48 try {
49 String s = scan.nextLine();
50 byte[] data = s.getBytes();
51 int len = data.length;
52 os.write(ChatUtil.int2byte(len));
53 os.write(data);
54 os.flush();
55 } catch (IOException e) {
56 e.printStackTrace();
57 break;
58 }
59 }
60 scan.close();
61 }
62
63 /**
64 * 读取消息长度
65 * 消息格式为：消息长度+消息内容
66 * @param is
67 * @return
68 * @throws IOException
69 */
70 public static int readLen(InputStream is) throws IOException {
71 int b1 = is.read();
72 int b2 = is.read();
73 int b3 = is.read();
74 int b4 = is.read();
75 int len = (b1 << 24) + (b2 << 16) + (b3 << 8) + b4;
76 return len;
77 }
78
79 /**
80 * int 转 byte[] 数组
81 * @param len
82 * @return
83 */
84 public static byte[] int2byte(int len) {
85 byte[] b = new byte[4];
86 b[0] = (byte) (len >> 24);
87 b[1] = (byte) (len >> 16 & 0XFF);
88 b[2] = (byte) (len >> 8 & 0XFF);
89 b[3] = (byte) (len & 0XFF);
90 return b;
91 }
92 }
93
