我试图一次将数据从服务器发送到客户端1位。无论何时从服务器收到一点，客户端都应该回复ACK。
当前发生的是当客户端将初始请求发送到服务器时，数据将传递到服务器。当服务器将所需数据发送到客户端时，数据将循环回自身，并且客户端将处于无限期等待挂起状态。
我已经为客户端和服务器附加了下面的代码。请看一下，并告诉我哪里出错了。
客户端：
import java.io.IOException;
import java.net.*;
import java.util.Scanner;
class UDPClient extends Thread implements Runnable
{
DatagramSocket clientSocket;
InetAddress IPAddress;
public static void main(String args[]) throws Exception
{
try
{
UDPClient t1 = new UDPClient();
Thread t = new Thread(t1);
t.start();
}
catch (Exception e)
{
System.out.println("Error!");
}
}
public UDPClient() throws Exception
{
this.clientSocket = new DatagramSocket();
this.IPAddress = InetAddress.getByName("Localhost");
clientSocket.setSoTimeout(5000);
}
public void run()
{
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String m ="1001";
String checksum = "1111";
String checksumSend = "";
String sentence="";
String sentence1="";
String dataRequired="";
try
{
dataRequired = dataRequired.concat(m+":Data");
sendData = dataRequired.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
checksumSend = checksumSend.concat(checksum+":checksum");
sendData = checksumSend.getBytes();
DatagramPacket sendPacket2 = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket2);
Scanner in = new Scanner(System.in);
System.out.println("Enter the Window size: ");
int s = in.nextInt();
String WinSize="";
WinSize = WinSize.concat(s+":Windowsize");
sendData = WinSize.getBytes();
DatagramPacket sendPacket3 = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket3);
String finished="Finished";
sendData = finished.getBytes();
DatagramPacket sendPacket6 = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket6);
do
{
try
{
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
System.out.println("I am getting executed");
clientSocket.receive(receivePacket); //After this step, nothing gets executed
sentence = new String(receivePacket.getData(),0,receivePacket.getLength());
System.out.println("Received from Server: " + sentence);
if(receivePacket != null)
sentence1 = "ACK";
sendData = sentence1.getBytes();
DatagramPacket sendPacket4 =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket4);
}
catch (SocketTimeoutException a)
{
System.out.println("Timed out!");
}
}while(sentence!=null);
}
catch (IOException e)
{
System.err.println(e);
}
finally
{
clientSocket.close();
}
}
}
服务器端：
import java.io.IOException;
import java.net.*;
public class UDPServer extends Thread implements Runnable
{
DatagramSocket serverSocket;
public static void main(String args[]) throws Exception
{
try
{
UDPServer t1 = new UDPServer();
Thread t = new Thread(t1);
t.start();
}
catch (Exception e)
{
System.out.println("Error!");
}
}
public UDPServer() throws Exception
{
this.serverSocket = new DatagramSocket(9876);
}
public void run()
{
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
String checksum="";
String Data = "";
String WinSize = "";
String carry = "0";
String output="";
String n,o;
String output1;
String sentence1="";
int i,j=0;
while(true)
{
String sentence="";
try
{
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
InetAddress IPAddress = receivePacket.getAddress();
sentence = new String( receivePacket.getData(),0,receivePacket.getLength());
if(sentence.contains("checksum"))
{
int len = sentence.length();
for(i=0;i<len;i++)
{
if(sentence.charAt(i)==':')
{
checksum = sentence.substring(0,i);
}
}
System.out.println("Checksum as specified by client is: " + checksum);
}
else if(sentence.contains("Data"))
{
int len = sentence.length();
for(i=0;i<len;i++)
{
if(sentence.charAt(i)==':')
{
Data = sentence.substring(0,i);
}
}
System.out.println("Data requested by client is: " + Data);
}
else if(sentence.contains("Windowsize"))
{
int len = sentence.length();
for(i=0;i<len;i++)
{
if(sentence.charAt(i)==':')
{
WinSize = sentence.substring(0,i);
}
}
System.out.println("Window Size is: " + WinSize);
}
else if(sentence.contains("Finished"))
{
output1 = checksumAdd(carry,Data,checksum);
output = reverse(output1);
System.out.println("Checksum Addition before complementing digits = "+output);
output = complement(output);
output = reverse(output);
System.out.println("Checksum Addition after complementing digits = "+output);
int WindowSize = Integer.parseInt(WinSize);
int strlen = Data.length();
do
{
for(i=j;i<(WindowSize+j);i++)
{
if(i!=strlen)
{
String send = "";
n = Data.substring(i,i+1);
System.out.println("Value of n is: "+n);
send = send.concat(n+":");
o = output.substring(i,i+1);
System.out.println("Value of o is: "+o);
send = send.concat(o);
sendData = send.getBytes();
DatagramPacket sendPacket1 = new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
serverSocket.send(sendPacket1);
}
else
break;
}
j+=WindowSize;
DatagramPacket receivePacket2 = new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket2);
sentence1 = new String( receivePacket2.getData(),0,receivePacket2.getLength());
System.out.println("sentence 1 is: "+sentence1); //To be removed. Used for testing purposes
}while(i!=strlen);
}
}
catch (IOException e)
{
System.err.println(e);
}
}
}
public static String complement(String output) {
String temp="";
int len = output.length();
for(int i=len;i>0;i--)
{
String t = output.substring(i-1,i);
if(t.equals("0"))
temp = temp.concat("1");
else if(t.equals("1"))
temp = temp.concat("0");
}
return temp;
}
public static String reverse(String output)
{
String temp="";
int len = output.length();
for(int i=len;i>0;i--)
{
String t = output.substring(i-1,i);
temp = temp.concat(t);
}
return temp;
}
public static String checksumAdd(String carry, String Data,String checksum)
{
int strlen = Data.length();
int flag=0;
String output="";
String output2="";
String n,che;
String sum = null;
for(int i=strlen;i>0;i--)
{
n=Data.substring(i-1,i);
che = checksum.substring(i-1,i);
if(n.equals("0") && che.equals("0") && carry.equals("0"))
{
sum = "0";
carry = "0";
}
else if(n.equals("0") && che.equals("0") && carry.equals("1"))
{
sum = "1";
carry = "0";
}
else if(n.equals("0") && che.equals("1") && carry.equals("0"))
{
sum = "1";
carry = "0";
}
else if(n.equals("0") && che.equals("1") && carry.equals("1"))
{
sum = "0";
carry = "1";
}
else if(n.equals("1") && che.equals("0") && carry.equals("0"))
{
sum = "1";
carry = "0";
}
else if(n.equals("1") && che.equals("0") && carry.equals("1"))
{
sum = "0";
carry = "1";
}
else if(n.equals("1") && che.equals("1") && carry.equals("0"))
{
sum = "0";
carry = "1";
}
else if(n.equals("1") && che.equals("1") && carry.equals("1"))
{
sum = "1";
carry = "1";
}
output = output.concat(sum);
}
if(carry.equals("1"))
{
n = output.substring(0,1);
if(n.equals("0"))
{
sum = "1";
carry = "0";
}
else if(n.equals("1"))
{
sum = "0";
carry = "1";
}
output2 = output2.concat(sum);
for(int i=strlen-1;i>0;i--)
{
n=Data.substring(i-1,i);
if(n.equals("0") && carry.equals("0"))
{
sum = "0";
carry = "0";
}
else if(n.equals("0") && carry.equals("1"))
{
sum = "1";
carry = "0";
}
else if(n.equals("1") && carry.equals("0"))
{
sum = "1";
carry = "0";
}
else if(n.equals("1") && carry.equals("1"))
{
sum = "0";
carry = "1";
}
output2 = output2.concat(sum);
}
flag = 1;
}
if (flag==1)
return output2;
return output;
}
}
如果您的客户端没有收到服务器的响应，可能是因为服务器没有发送响应。
serverSocket.send（sendPacket1）;只调用if（i！= strlen）
您是否尝试在if块中的控制台中输出一些文本以查看是否/何时进入该循环？