我试图发送一个DatagramPacket,然后必须等待来自服务器的Acknowlegment,以便我知道是否必须重新发送相同的数据包或发送下一个数据包..
我在客户端使用相同的套接字,发送数据包并接收确认(ack),在服务器端使用相同的套接字,另一个用于接收datapacket然后将确认发送给客户端..
第一个问题是客户端正在发送数据包,服务器正在接收它,然后将确认发送给客户端,但客户端在接收确认数据包时阻塞。
我正在制作一些System.out.println以确定问题所在,但我无法找到解决此问题的方法。
第二个问题是服务器仍然总是接收数据,并且不等待客户端发送内容,我检查了因为我得到了这些行(例如"得到长度为xxx&#34的数据包;&# 34; ack发送给ackNr yyy" ..."打印在服务器端,虽然客户端在发送第一个数据包后阻塞,因为它正在等待确认未收到!
以下是客户代码:
package blatt7;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketTimeoutException;
import java.net.UnknownHostException;
import java.nio.ByteBuffer;
import java.util.zip.CRC32;
public class FileSender {
String zielRechner;
String filePath;
InetAddress host;
File file;
FileInputStream fis;
int readLength;
int sequenceNr = 0;
int receivedSeqNr = 1;
static int port = 7777;
int packetNr = 0;
byte[] packet = new byte[1216];
byte[] data = new byte[1200];
byte[] header = new byte[16];
byte[] readLengthByte = new byte[4];
byte[] sequenceNrByte = new byte[4];
byte[] checksumByte = new byte[8];
byte[] ackBuffer = new byte[4];
CRC32 checksumCalculator = new CRC32();
DatagramPacket dp;
DatagramPacket ackPacket;
DatagramSocket sendSocket = null;
//DatagramSocket ackSocket = null;
static boolean ackReceived = true;
public FileSender(String zielRechner, String filePath) throws UnknownHostException, FileNotFoundException {
this.zielRechner = zielRechner;
this.filePath = filePath;
this.host = InetAddress.getByName(zielRechner);
this.file = new File(filePath);
fis = new FileInputStream(file);
}
public void sendFile() throws IOException {
while((readLength = fis.read(data)) != -1) {
if (sequenceNr == 1)
sequenceNr = 0;
else
sequenceNr = 1;
readLengthByte = intToBytes(readLength);
sequenceNrByte = intToBytes(sequenceNr);
for(int i=0; i<4; i++) {
header[8+i] = readLengthByte[i];
}
for(int i=0; i<4; i++) {
header[12+i] =sequenceNrByte[i];
}
int j=0;
for (int i=0; i<packet.length; i++) {
if (i < header.length)
packet[i] = header[i];
else {
packet[i] = data[j];
j++;
}
}
checksumCalculator.reset();
checksumCalculator.update(packet,8,8+readLength);
checksumByte = longToBytes(checksumCalculator.getValue());
for(int i=0; i < 8; i++) {
packet[i] = checksumByte[i];
}
dp = new DatagramPacket(packet, packet.length, host, port);
while(receivedSeqNr == sequenceNr && ackReceived) {
try {
ackReceived = false;
sendSocket = new DatagramSocket();
sendSocket.send(dp);
sendSocket.setSoTimeout(10000);
packetNr++;
System.out.println("Packet sent with seqNr: " + sequenceNr + " and length: " + bytesToInt(readLengthByte, 0) + " - PACKET NR: " + packetNr);
ackPacket = new DatagramPacket(ackBuffer, ackBuffer.length);
System.out.println("TEST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
sendSocket.receive(ackPacket);
System.out.println("Receiving ACK!!");
ackReceived = true;
ackBuffer = ackPacket.getData();
receivedSeqNr = bytesToInt(ackBuffer,0);
System.out.println("got SequenceNr with receivedSeq-Nr: " + receivedSeqNr);
} catch (SocketTimeoutException e) {
e.printStackTrace();
break;
}
}
}
fis.close();
System.out.println("Transfer Completed Successfully!");
sendSocket.close();
}
public static byte[] longToBytes(long value) {
ByteBuffer buffer = ByteBuffer.allocate(8);
buffer.putLong(value);
return buffer.array();
}
public static long bytesToLong(byte[] bytes, int index) {
ByteBuffer buffer = ByteBuffer.allocate(8);
buffer.put(bytes);
buffer.flip();//need flip
return buffer.getLong(index);
}
public static byte[] intToBytes(int value) {
ByteBuffer buffer = ByteBuffer.allocate(4);
buffer.putInt(value);
return buffer.array();
}
public static int bytesToInt(byte[] bytes, int index) {
ByteBuffer buffer = ByteBuffer.allocate(4);
buffer.put(bytes);
buffer.flip();//need flip
return buffer.getInt(index);
}
public static void main(String[] args) throws IOException,ClassNotFoundException {
FileSender sender = new FileSender("localhost", "C:/Users/Kb/Desktop/Deepophile - Psychedelic Sessions.wav");
sender.sendFile();
}
}
这是SERVER的代码:
package blatt7;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.zip.CRC32;
public class FileReceiver {
byte[] incomingBuffer;
DatagramPacket incomingPacket;
DatagramSocket receiveSocket;
DatagramPacket ackPacket;
int packetCounter = 0;
int dataLength;
int receivedSeqNr;
long calculatedChecksum;
long receivedChecksum;
CRC32 checksumCalculator = new CRC32();
byte[] dataLengthByte = new byte[4];
byte[] receivedSeqNrByte = new byte[4];
byte[] receivedChecksumByte = new byte[8];
byte[] ackArray;
public FileReceiver() throws SocketException {
incomingBuffer = new byte[1500];
incomingPacket = new DatagramPacket(incomingBuffer, incomingBuffer.length);
}
public void receive() throws IOException {
receiveSocket = new DatagramSocket(FileSender.port);
receiveSocket.setSoTimeout(10000);
System.out.println("Server socket created. Waiting for incoming data...");
while(true && FileSender.ackReceived)
{
receiveSocket.receive(incomingPacket);
packetCounter++;
for (int i=0; i <4; i++) {
dataLengthByte[i] = incomingBuffer[8+i];
}
dataLength = FileSender.bytesToInt(dataLengthByte,0);
checksumCalculator.reset();
checksumCalculator.update(incomingBuffer, 8, dataLength+8);
calculatedChecksum = checksumCalculator.getValue();
for (int i=0; i <4; i++) {
receivedSeqNrByte[i] = incomingBuffer[12+i];
}
receivedSeqNr = FileSender.bytesToInt(receivedSeqNrByte,0);
for (int i=0; i <8; i++) {
receivedChecksumByte[i] = incomingBuffer[i];
}
long receivedChecksum = FileSender.bytesToLong(receivedChecksumByte,0);
System.out.println("Got packet with checksum: " + receivedChecksum);
System.out.println("Server-calculated checksum: " + calculatedChecksum);
System.out.println("Got packet with seqNr: " + receivedSeqNr + " and length: " + dataLength);
if (calculatedChecksum != receivedChecksum) {
sendACK(receivedSeqNr);
System.out.println("Packet have erros(s)! It must be sent another time!");
}
else if(calculatedChecksum == receivedChecksum && receivedSeqNr == 1) {
sendACK(0);
System.out.println("SeqNr '0' sent");
}
else if (calculatedChecksum == receivedChecksum && receivedSeqNr == 0) {
sendACK(1);
System.out.println("SeqNr '1' sent");
}
}
}
public void sendACK(int seqNum) throws IOException {
byte[] ackArray = FileSender.intToBytes(seqNum);
ackPacket = new DatagramPacket(ackArray, ackArray.length, InetAddress.getByName("localhost"), FileSender.port);
receiveSocket.send(ackPacket);
}
public static void main(String[] args) throws IOException,ClassNotFoundException {
FileReceiver receiver = new FileReceiver();
receiver.receive();
}
}
您可以尝试执行它以查看问题所在...... 所以,如果你有任何想法我怎么能解决这个问题,请告诉我!
非常感谢!
有谁能告诉我在哪里可以找到收到的文件?或者我应该如何更改我的代码以便我选择保存它的位置?
答案 0 :(得分:3)
是的,这是可能的。您的问题是您在发送ACK数据报时遇到目标地址:端口错误。您应该从接收到的DatagramPacket获取目标地址:端口,或者更简单的是重用将具有不同数据的数据报作为ACK数据报。
答案 1 :(得分:1)
服务器如何使用自己的端口发送到客户端?您正在服务器端口上从服务器向客户端发送ACK,您应该从接收到的数据包中获取客户端的UDP端口并将数据发送到该端口。
修改强>
将SendACK方法中的服务器更改为:
ackPacket = new DatagramPacket(ackArray, ackArray.length, InetAddress.getByName("localhost"), incomingPacket.getPort());
现在通过运行来分析代码。