Java Socket编程实例（五）

Java Socket编程实例（五）

一、回传协议接口和UDP方式实现：

1.接口：

import java.nio.channels.SelectionKey;

import java.io.IOException;

public interface EchoProtocol {

void handleAccepxnyfgSt(SelectionKey key) throws IOException;

void handleRead(SelectionKey key) throws IOException;

void handleWrite(SelectionKey key) throws IOException;

}

2.实现：

import java.net.SocketAddress;

import java.nio.channels.*;

import java.nio.ByteBuffer;

import java.io.IOException;

public class UDPEchoSelectorProtocol implements EchoProtocol {

private static final int ECHOMAX = 255; // Maximum size of echo datagram

static class ClientRecord {

public SocketAddress clientAddress;

public ByteBuffer buffer = ByteBuffer.allocate(ECHOMAX);

}

public void handleAccept(SelectionKey key) throws IOException {

}

public void handleRead(SelectionKey key) throws IOException {

DatagramChannel channel = (DatagramChannel) key.channel();

ClientRecord clntRec = (ClientRecord) key.attachment();

clntRec.buffer.clear(); // Prepare buffer for receiving

clntRec.clientAddress = channel.receive(clntRec.buffer);

if (clntRec.clientAddress != null) { // Did we receive something?

// Register write with the selector

key.interestOps(SelectionKey.OP_WRITE);

}

}

public void handleWrite(SelectionKey key) throws IOException {

DatagramChannel channel = (DatagramChannel) key.channel();

ClientRecord clntRec = (ClientRecord) key.attachment();

clntRec.buffer.flip(); // Prepare buffer for sending

int bytesSent = channel.send(clntRec.buffer, clntRec.clientAddress);

if (bytesSent != 0) { // Buffer completely written?

// No longer interested in writes

key.interestOps(SelectionKey.OP_READ);

}

}

}

二、NIO UDP客户端：

import java.net.InetSocketAddress;

import java.net.SocketException;

import java.nio.ByteBuffer;

import java.nio.channels.DatagramChannel;

public class UDPEchoClientNonblocking {

private static final int TIMEOUT = 3000; // Resend timeout (milliseconds)

private static final int MAXTRIES = 255; // Maximum retransmissions

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

// Convert input String to bytes using the default charset

byte[] bytesToSend = "0123456789abcdefghijklmnopqrstuvwxyz".getBytes();

// Create channel and set to nonblocking

DatagramChannel datagramChannel = DatagramChannel.open();

datagramChannel.configureBlocking(false);

datagramChannel.socket().setSoTimeout(TIMEOUT);

ByteBuffer writeBuf = ByteBuffer.wrap(bytesToSend);

ByteBuffer readBuf = ByteBuffer.allocate(MAXTRIES);

datagramChannel = datagramChannel.connect(new InetSocketAddress("127.0.0.1", 5500));

int totalBytesRcvd = 0; // Total bytes received so far

int bytesRcvd; // Bytes received in last read

while (totalBytesRcvd < bytesToSend.length) {

if (writeBuf.hasRemaining()) {

datagramChannel.write(writeBuf);

}

if ((bytesRcvd = datagramChannel.read(readBuf)) == -1) {

throw new SocketException("Connection closed prematurely");

}

totalBytesRcvd += bytesRcvd;

System.out.print("."); // Do something else

}

System.out.println("Received: " + new String(readBuf.array(), 0, totalBytesRcvd));

datagramChannel.close();

}

}

三、NIO UDP服务端：

import java.io.IOException;

import java.net.InetSocketAddress;

import java.nio.channels.*;

import java.util.Iterator;

public class UDPEchoServerSelector {

private static final int TIMEOUT = 3000; // Wait timeout (milliseconds)

public static void main(String[]http:// args) throws IOException {

// Create a selector to multiplex client connections.

Selector selector = Selector.open();

DatagramChannel channel = DatagramChannel.open();

channel.configureBlocking(false);

channel.socket().bind(new InetSocketAddress(5500));

channel.register(selector, SelectionKey.OP_READ, new UDPEchoSelectorProtocol.ClientRecord());

UDPEchoSelectorProtocol echoSelectorProtocol = new UDPEchoSelectorProtocol();

while (true) { // Run forever, receiving and echoing datagrams

// Wait for task or until timeout expires

if (selector.select(TIMEOUT) == 0) {

System.out.print(".");

continue;

}

// Get iterator on set of keys with I/O to process

Iterator keyIter = selector.selectedKeys().iterator();

while (keyIter.hasNext()) {

SelectionKey key = keyIter.next(); // Key is bit mask

// Client socket channel has pending data?

if (key.isReadable())

echoSelectorProtocol.handleRead(key);

// Client socket channel is available for writing and

// key is valid (i.e., channel not closed).

if (key.isValid() && key.isWritable())

echoSelectorProtocol.handleWrite(key);

keyIter.remove();

}

}

}

}

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