概述
Java 网络编程的客户端和服务端编写都非常简单。客户端使用 Socket 对象与服务端交互；服务端创建 ServerSocket 对象，然后使用accept()方法进行监听，并返回一个Socket的对象。accept 方法是阻塞调用，并将一直阻塞，直到接收到下一个客户端请求为止。非多线程情况下，服务器同时只能服务一个客户端。这通常是不能满足现实需求的。
对于现实场景是通过在服务端创建多个线程来服务多个客户端，如下图：
服务端
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| import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.concurrent.ExecutorService
;
import java.util.concurrent.Executors;
public class EchoMultiServer {
private static ServerSocket server = null;
private static ExecutorService threadPool;
public static void main(String[] args) {
threadPool = Executors.newCachedThreadPool();
threadPool.submit(new Monitor
());
try {
server = new ServerSocket(10000);
System.out.println("Server listening on port 10000 ....");
System.out.println("Hit Enter to stop the server");
while (true) {
Socket socket = server.accept();
System.out.println("Thread created");
threadPool.submit(new EchoThread
(socket));
}
} catch (SocketException e) {
System.out.println("Server is down");
} catch (IOException e) {
e.printStackTrace();
}
}
private static void shutdownServer() {
try {
server.close();
} catch (IOException e) {
e.printStackTrace();
}
threadPool.shutdown();
System.exit(0);
}
private static class Monitor implements Runnable {
@Override
public void run() {
try {
while (System.in.read() != '\n') {}
} catch (IOException e) {
}
shutdownServer();
}
}
}
class EchoThread implements Runnable {
private Socket socket = null;
private byte[] buffer = new byte[512];
public EchoThread(Socket socket) {
this.socket = socket;
}
@Override
public void run() {
try {
InputStream is = socket.getInputStream();
is.read(buffer);
OutputStream os = socket.getOutputStream();
os.write(buffer);
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
|
客户端
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| import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetSocketAddress
;
import java.net.Socket;
import java.util.Scanner;
public class EchoMultiClient {
private static int counter;
public static void main(String[] args) {
for (int i = 0; i < 100; i++) {
counter++;
new Thread(new Client(counter)).start();
}
}
private static class Client implements Runnable {
private int counter;
public Client(int counter) {
this.counter = counter;
}
@Override
public void run() {
try {
Socket socket = new Socket();
socket.connect(new InetSocketAddress("localhost", 10000), 1000);
try {
OutputStream os = socket.getOutputStream();
String str = "Hello from Client " + counter;
os.write(str.getBytes());
InputStream is = socket.getInputStream();
Scanner scanner = new Scanner(is);
while (scanner.hasNextLine()) {
System.out.println(scanner.nextLine());
}
Thread.sleep(10);
scanner.close();
} finally {
socket.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
|