java IO笔记(网络中IO的运用)

如今大部分的编程开发都离不开网络，Java IO同样可以基于网络进行开发。事实上网络编程可以看做两个进程之间的通信，我们可以通过java对网络的支持，建立两点的网络连接，连接建立成功之后，就可以看做是本地的文件操作了。前面对于文件进行的类似操作也可以适用在这里。

我们常用的有TCP/UDP建立连接，下面将分别举例说明：

TCPClient:

 

package NetIo;

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

public class TCPClient {
	private Socket socket;
	private boolean connectFlag;
	private InputStream is;
	private OutputStream os;
	private byte[] buffer = new byte[1024];

	public static void main(String[] args) {
		TCPClient client = new TCPClient();
		if (client.initSocket()) {
			client.execute();
		} else {
			System.out.println("the connect has some wrong.");
		}
	}

	private boolean initSocket() {
		try {
			socket = new Socket("127.0.0.1", 5008);
			socket.setSoTimeout(2000);
			connectFlag = true;
		} catch (IOException e) {
			e.printStackTrace();
		}
		return connectFlag;
	}

	private void execute() {
		String message = "Hello World!";
		try {
			is = socket.getInputStream();
			os = socket.getOutputStream();

			int len;
			os.write(message.getBytes());
			while (true) {
				len = is.read(buffer);
				if (len != -1) {
					String response = new String(buffer, 0, len);
					System.out.println("从服务器接收的消息为" + response);
					break;
				}
			}
			socket.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
}

TCPServer:

 

 

package NetIo;

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

public class TCPServer implements Runnable{
	private ServerSocket serversocket;
	private Socket socket;
	private boolean connectFlag;
	private InputStream is;
	private OutputStream os;
	private byte[] buffer = new byte[1024];
	
	public TCPServer(){
	}
	
	public TCPServer(Socket socket){
		this.socket = socket;
	}
	
	public static void main(String[] args) {
		TCPServer server = new TCPServer();
		if(server.initServer()){
			server.execute();
		}else {
			System.out.println("there are some mistakes when connect");
		}
	}
	
	private boolean initServer(){
		try {
			serversocket = new ServerSocket(5008);
			connectFlag = true;
		} catch (IOException e) {
			e.printStackTrace();
		}
		return connectFlag;
	}
	
	private void execute(){
		while(true){
			try {
				socket = serversocket.accept();
				new Thread(new TCPServer(socket)).start();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
	
	@Override
	public void run() {
		try {
			
			String host = socket.getInetAddress().toString();
			int port = socket.getPort();
			os = socket.getOutputStream();
			is = socket.getInputStream();
			while(true){
				if(socket.isClosed()){
					return;
				}
				int len = is.read(buffer);
				if(len != -1){
					System.out.println("从地址为"+host+"端口为"+port+"的客户端发来消息："+new String(buffer,0,len));
					os.write("服务器已接收消息成功".getBytes());
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		
	}

}

 

先执行服务端，在执行客户端代码，可以在控制台看到如下打印：

上面的两个例子模拟了TCP通信，从中可以看出IO在网络编程中也是有着一席之地的。

下面将举例说明基于UDP的网络IO。

UDPClient：

 

package NetIo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;

public class UDPClient {

	public static void main(String[] args) throws IOException {
		DatagramSocket socket = new DatagramSocket();
		String message = "Hello World!";
		byte[] buffer = message.getBytes();
		InetAddress address = InetAddress.getByName("127.0.0.1");
		DatagramPacket packet = new DatagramPacket(buffer, buffer.length,
				address, 5000);
		socket.send(packet);
		while (true) {
			byte[] buf = new byte[1024];
			DatagramPacket receivePacket = new DatagramPacket(buf, buf.length);
			socket.receive(receivePacket);
			String response = new String(receivePacket.getData(), 0,
					receivePacket.getData().length);
			if (response != null) {
				System.out.println("从服务端成功接收消息：" + response);
				socket.close();
				break;
			}
		}
	}

}

 

UDPServer:

 

package NetIo;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.concurrent.atomic.AtomicInteger;

public class UDPServer implements Runnable {
	private DatagramSocket socket;
	private DatagramPacket packet;

	public UDPServer(DatagramSocket socket, DatagramPacket packet) {
		this.socket = socket;
		this.packet = packet;

	}

	public static void main(String[] args) throws IOException {
		AtomicInteger numThreads = new AtomicInteger(0);
		DatagramSocket socket = new DatagramSocket(5000);
		while (true) {
			byte[] buf = new byte[1024];
			DatagramPacket packet = new DatagramPacket(buf, buf.length);
			socket.receive(packet);
			Thread thread = new Thread(new UDPServer(socket, packet));
			thread.start();
			numThreads.incrementAndGet();
		}
	}

	@Override
	public void run() {
		String message = new String(packet.getData(), 0,
				packet.getData().length);
		int port = packet.getPort();
		InetAddress address = packet.getAddress();
		System.out.println("get a message from address:" + address + " port："
				+ port + " message:" + message);
		String respose = "服务器已成功收到消息";
		DatagramPacket resPacket = new DatagramPacket(respose.getBytes(),
				respose.getBytes().length, address, port);
		try {
			socket.send(resPacket);
		} catch (IOException e) {
			e.printStackTrace();
		}

	}
}

先执行服务端，在执行客户端代码，可以在控制台看到如下打印：

 

上面的两个例子模拟了UDP简单通信。