网络编程之：UDP客户端

[code]
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.SocketException;

/**
* UDP客户端
*
*/
public class UDPClient {
// *********常数*********

private static final int DEFAULT_RECEIVE_BUFFER_SIZE = 8192;
private static final int DEFAULT_SO_TIMEOUT = 30000;

// *********成员变量*********

private SocketAddress serverSocketAddress;
private byte[] sendData;
private DatagramPacket output;

private int receiveBufferSize; // in bytes
private DatagramSocket ds;

// *********构造函数*********

/**
*
* 构建一个UDPClient对象。
*
* @param serverAddress 服务地址
* @param serverPort 服务器监听端口
* @throws SocketException
*/
public UDPClient(String serverAddress, int serverPort) throws SocketException {
this(serverAddress, serverPort, new byte[1], DEFAULT_RECEIVE_BUFFER_SIZE, DEFAULT_SO_TIMEOUT);
}

/**
*
* 构建一个UDPClient对象。
*
* @param serverAddress 服务地址
* @param serverPort 服务器监听端口
* @param sendData 发送的数据
* @throws SocketException
*/
public UDPClient(String serverAddress, int serverPort, byte[] sendData) throws SocketException {
this(serverAddress, serverPort, sendData, DEFAULT_RECEIVE_BUFFER_SIZE, DEFAULT_SO_TIMEOUT);
}

/**
*
* 构建一个UDPClient对象。
*
* @param serverAddress 服务地址
* @param serverPort 服务器监听端口
* @param sendData 发送的数据
* @param receiveBufferSize 接收缓存大小
* @throws SocketException
*/
public UDPClient(String serverAddress, int serverPort, byte[] sendData, int receiveBufferSize)
throws SocketException {
this(serverAddress, serverPort, sendData, receiveBufferSize, DEFAULT_SO_TIMEOUT);
}

/**
*
* 构建一个UDPClient对象。
*
* @param serverAddress 服务地址
* @param serverPort 服务器监听端口
* @param sendData 发送的数据
* @param receiveBufferSize 接收缓存大小
* @param timeout 超时
* @throws SocketException
*/
public UDPClient(String serverAddress, int serverPort, byte[] sendData, int receiveBufferSize, int timeout)
throws SocketException {
SocketAddress sa = new InetSocketAddress(serverAddress, serverPort);
this.serverSocketAddress = sa;
this.sendData = sendData;
this.output = new DatagramPacket(sendData, sendData.length, sa);

this.receiveBufferSize = receiveBufferSize;
this.ds = new DatagramSocket(0);
this.ds.setSoTimeout(timeout);
}

// *********成员方法*********

/**
*
* 构建一个UDPClient对象。
*
* @param serverAddress 服务地址
* @param serverPort 服务器监听端口
* @param sendData 发送的数据
* @param receiveBufferSize 接收缓存大小
* @param timeout 超时
* @throws SocketException
*/
public void setServerSocketAddress(SocketAddress serverSocketAddress) {
this.serverSocketAddress = serverSocketAddress;
}

/**
*
* 构建一个UDPClient对象。
*
* @param serverAddress 服务地址
* @param serverPort 服务器监听端口
* @param sendData 发送的数据
* @param receiveBufferSize 接收缓存大小
* @param timeout 超时
* @throws SocketException
*/
public void setSendData(byte[] sendData) {
this.sendData = sendData;
}

/**
* 发送数据并且接受数据。
*/
public byte[] sendAndReceive() throws IOException {
send();
return receive();
}

/**
* 只发送数据。
*/
public void send() throws IOException {
output.setSocketAddress(serverSocketAddress);
output.setData(sendData);
output.setLength(sendData.length);

ds.connect(serverSocketAddress);
ds.send(output);
}

/**
* 接收数据。
*/
public byte[] receive() throws IOException {
byte[] response = null;
DatagramPacket input = new DatagramPacket(new byte[receiveBufferSize], receiveBufferSize);
// next line blocks until the response is received
ds.receive(input);
int numBytes = input.getLength();
response = new byte[numBytes];
System.arraycopy(input.getData(), 0, response, 0, numBytes);

// may return null
return response;
}

/**
* 关闭Socket。
*/
public void close() {
this.ds.close();
}
}
[/code]

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