这是一个任务，我正在尝试几种不同的方法来处理：
我们已经使用 UDP 来模拟 TCP。今天早些时候，我设法让文件传输通过 UDP 工作，但当然我没有检查重新发送“段”的错误，所以我没有尝试实现一个带有 ID 和一些字节数据的消息类型类。
调试显示我正确地制作了我的消息对象，然后我使用 public byte[]serialize(Object obj)将我的对象转换为用于 UDP 数据报传输的字节数组。
在接收端，当我将反序列化的对象转换回消息时，它崩溃了。
铸造失败
Message receiveMSG = null;
try {
receiveMSG = (Message)deserialize(receivedPacket.getData());
} catch (ClassNotFoundException ex) {
Logger.getLogger(UDPReceiver.class.getName()).log(Level.SEVERE, null, ex);
}
反序列化方法
private Object deserialize(byte[] bytes) throws IOException, ClassNotFoundException {
ByteArrayInputStream b = new ByteArrayInputStream(bytes);
ObjectInputStream o = new ObjectInputStream(b);
return (Message)o.readObject();
}
任何人都可以发现为什么这个演员会失败？谢谢你。
消息类
public class Message implements Serializable {
private int segmentID;
private byte[] packet;
public Message(int segmentID, byte[] packet)
{
this.segmentID = segmentID;
this.packet = packet;
}
public int getSegmentID()
{
return segmentID;
}
public byte[] getPacket()
{
return packet;
}
}
UDPSENDER 类
public class UDPSender implements Sender{
private File theFile;
private FileInputStream fileReader;
private DatagramSocket datagramSocket;
private int fileLength, currentPos, bytesRead, toPort;
private byte[] msg, buffer;
private String toHost,initReply;
private InetAddress toAddress;
private int segmentID;
public UDPSender(InetAddress address, int port) throws IOException{
toPort = port;
toAddress = address;
msg = new byte[512];
buffer = new byte[512];
datagramSocket = new DatagramSocket();
datagramSocket.connect(toAddress, toPort);
segmentID = 0;
}
@Override
public void sendFile(File theFile) throws IOException{
// Init stuff
fileReader = new FileInputStream(theFile);
fileLength = fileReader.available();
System.out.println(" -- Filename: "+theFile.getName());
System.out.println(" -- Bytes to send: "+fileLength);
send((theFile.getName()+"::"+fileLength).getBytes());
DatagramPacket reply = new DatagramPacket(buffer, buffer.length);
datagramSocket.receive(reply);
if (new String(reply.getData(), 0, reply.getLength()).equals("OK"))
{
System.out.println(" -- Got OK from receiver - sending the file ");
int length;
while (currentPos<fileLength){
bytesRead = fileReader.read(msg);
Message message = new Message(1,msg);
send(serialize(message));
currentPos = currentPos + bytesRead;
}
System.out.println(" -- File transfer complete...");
}
else{System.out.println("Recieved something other than OK... exiting");}
}
private void send(byte[] message, int length) throws IOException {
DatagramPacket packet =
new DatagramPacket(message, length);
datagramSocket.send(packet);
}
private void send(byte[] message) throws IOException {
DatagramPacket packet =
new DatagramPacket(message, message.length);
datagramSocket.send(packet);
}
public byte[] serialize(Object obj) throws IOException {
ByteArrayOutputStream b = new ByteArrayOutputStream();
ObjectOutputStream o = new ObjectOutputStream(b);
o.writeObject(obj);
return b.toByteArray();
}
}
UDP接收器
public class UDPReceiver {
DatagramSocket socket;
String filename, initString;
byte[] buffer;
DatagramPacket initPacket, receivedPacket;
FileOutputStream fileWriter;
int bytesReceived, bytesToReceive;
public UDPReceiver(int port) throws IOException {
// Init stuff
socket = new DatagramSocket(port);
buffer = new byte[516];
System.out.println(" -- Ready to receive file on port: " + port);
initPacket = receivePacket();
initString = "Recieved-" + new String(initPacket.getData(), 0, initPacket.getLength());
StringTokenizer t = new StringTokenizer(initString, "::");
filename = t.nextToken();
bytesToReceive = new Integer(t.nextToken()).intValue();
System.out.println(" -- The file will be saved as: " + filename);
System.out.println(" -- Expecting to receive: " + bytesToReceive + " bytes");
send(initPacket.getAddress(), initPacket.getPort(), (new String("OK")).getBytes());
fileWriter = new FileOutputStream(filename);
while (bytesReceived < bytesToReceive) {
receivedPacket = receivePacket();
Message receiveMSG = null;
try {
receiveMSG = (Message)deserialize(receivedPacket.getData());
} catch (ClassNotFoundException ex) {
Logger.getLogger(UDPReceiver.class.getName()).log(Level.SEVERE, null, ex);
}
System.out.println(receiveMSG.getSegmentID());
// System.out.println(bytesReceived);
// send(initPacket.getAddress(), initPacket.getPort(), (new String("OK")).getBytes());
}
System.out.println(" -- File transfer complete.");
}
public DatagramPacket receivePacket() throws IOException {
DatagramPacket packet =
new DatagramPacket(buffer, buffer.length);
socket.receive(packet);
return packet;
}
public byte[] receiveData() throws IOException {
DatagramPacket packet =
new DatagramPacket(buffer, buffer.length);
socket.receive(packet);
return packet.getData();
}
public void send(InetAddress recv, int port, byte[] message)
throws IOException {
DatagramPacket packet =
new DatagramPacket(message, message.length, recv, port);
socket.send(packet);
}
private Object deserialize(byte[] bytes) throws IOException, ClassNotFoundException {
ByteArrayInputStream b = new ByteArrayInputStream(bytes);
ObjectInputStream o = new ObjectInputStream(b);
return (Message)o.readObject();
}
}