好的，所以我一直遇到一些问题让我的代码工作，所以我制作了一个简化版本的程序来弄清楚发生了什么，但我仍然感到困惑。
以下是该计划：
这是服务器代码：
public class Server{
private ServerSocket server;
private Socket connection;
private DatagramSocket server_socket;
String compString = "";
public static List<String> messages = Collections.synchronizedList(new ArrayList<String>());
public static List<DatagramPacket> packets = Collections.synchronizedList(new ArrayList<DatagramPacket>());
public Server()
{
}
public void startRunning()
{
try
{
server_socket = new DatagramSocket(9876);
receiveAndSend();
}catch(Exception e)
{
System.out.println("Exception caught");
}
}
public void receiveAndSend()
{
Thread thread1 = new Thread()
{
public void run()
{
try{
while(true)
{
byte[] buffer = new byte[3000];
DatagramPacket request = new DatagramPacket(buffer, buffer.length);
server_socket.receive(request);
String mess = new String(request.getData());
synchronized(messages)
{
if(!messages.contains(mess) && !packets.contains(request))
{
addMessage(mess);
addPacket(request);
System.out.println("added: " + mess);
}
}
}
}catch(Exception e)
{
System.out.println("Exception caught");
}
}
};
thread1.start();
Thread thread2 = new Thread()
{
public void run()
{
try
{
while(true)
{
Thread.sleep(6000);
System.out.println("the list contains");
synchronized(messages)
{
compString = "";
for (String st : messages)
{
System.out.println(st);
}
System.out.println("!!!!!!!!!!!!!!!!!!");
if(!messages.isEmpty())
{
System.out.println(messages.size());
for(int i=0; i< messages.size(); i++)
{
compString += messages.get(i);
compString += "-";
}
}
}
System.out.println("final string is:" + compString + "\n");
for(DatagramPacket pack: packets)
{
try
{
InetAddress add = pack.getAddress();
int port = pack.getPort();
byte[] tbuffer = compString.getBytes();
DatagramPacket reply = new DatagramPacket(tbuffer, tbuffer.length, add, port);
server_socket.send(reply);
}catch(Exception e)
{
System.out.println("Exception caught");
}
}
}
}catch(Exception e)
{
}
}
};
thread2.start();
}
public synchronized void addMessage(String mess)
{
messages.add(mess);
}
public synchronized void addPacket(DatagramPacket packet)
{
packets.add(packet);
}
}
这是客户端代码：
public class Client {
public String message;
public int port;
public int server = 9876;
public void Client(String message)
{
this.message = message;
}
public void startRunning()
{
serverStart();
}
public void serverStart()
{
Thread thread1 = new Thread()
{
public void run()
{
try{
DatagramSocket ssocket = new DatagramSocket(port);
while(true)
{
Thread.sleep(5000);
byte [] m =message.getBytes();
InetAddress hhost = InetAddress.getByName("127.0.0.1"); //won't be always localh
DatagramPacket request = new DatagramPacket(m, m.length, hhost, server);
ssocket.send(request);
System.out.println("sending: " + message + "\n");
byte[] buffer = new byte[2000];
DatagramPacket reply = new DatagramPacket(buffer, buffer.length);
ssocket.receive(reply);
String receivedString = new String(reply.getData());
System.out.println("receivedString : " + receivedString);
if(receivedString != null && !receivedString.isEmpty())
{
}
}
}catch(Exception e)
{
System.out.println("Exception caught");
}
}
};
thread1.start();
}
public String[] convertStringToArray(String tstring)
{
tstring.trim();
String[] sarray = tstring.split("-");
return sarray;
}
}
你需要这3个来运行代码：
public class ServerTest {
public static void main(String[] args)
{
Server s = new Server();
s.startRunning();
}
}
public class ClientTest2 {
public static void main(String[] args)
{
Client myclient = new Client();
myclient.message = "Hello";
myclient.port = 6965;
myclient.startRunning();
}
}
public class ClientTest {
public static void main(String[] args)
{
Client myclient = new Client();
myclient.message = "Kitty";
myclient.port = 6646;
myclient.startRunning();
}
}
我运行时得到以下输出：
added: Helloadded: Kittythe list contains
Hello2
final string is:Hellothe list contains
Hello
!!!!!!!!!!!!!!!!!!
2
final string is:Hello
the list contains
Hello
!!!!!!!!!!!!!!!!!!
问题在于：1）println有时会被打断并且永远不会运行，在上面的输出中我们可以看到该行!!!!!!!!!!!!!!有时不打印出来。 2）Arraylist中的某些元素不会被添加或不会被打印。
我确实试图在任何地方放置同步块，但它似乎没有用，以及其他各种没有帮助的东西。
答案 0 :(得分：0)
您未正确序列化/反序列化字符串。
在您的服务器中，您应指定从接收缓冲区获取的数据的字节范围，以及客户端使用的编码：
String receivedString = new String(reply.getData(), 0, reply.getLength(), "UTF-8");
在您的客户端中，您应指定用于序列化字符串的编码：
byte[] m = message.getBytes("UTF-8");
此外，DatagramPacket.equals()仅进行引用比较（即，只有在传递对自身的引用时才返回true;它不会将另一个数据包中的数据与自己的数据进行比较），所以{{ 1}}永远都是真的。