java - 如何确保所有数据包均已收到并存储在数组中？

Question

1) 在 Java 无连接套接字编程中，如何确保来自 5 个处理器的所有数据包均已收到并在到达时存储在数组中？基本上，我想收集属于多播组的所有进程(其中 5 个)发送的所有部分和，并将这些部分和存储在一个数组中，然后我将在该数组上执行一些操作。

2)另外，我希望了解如何在同一代码中查找整数数组的给定元素的索引。我需要执行的操作之一是找到数组的最大值并检索其索引。

下面是我的线程代码片段，其中包含接收方法。

readThread(InetAddress g, int port){

    group = g;
    multicastPort = port;
}

public void run(){

    try {
        MulticastSocket readSocket = new MulticastSocket(multicastPort);
        readSocket.joinGroup(group);

        while (true) {
            byte[] recvBuffer = new byte[MAX_MSG_LEN];
            DatagramPacket packet = new DatagramPacket(recvBuffer, recvBuffer.length, group, multicastPort);

            readSocket.receive(packet);

            String rString = new String(packet.getData());
            String message = new String(rString.getBytes()).trim();                             // Process the received message before use here

            StringTokenizer stk = new StringTokenizer(message, ",");

            int recvdProcessID = Integer.parseInt(stk.nextToken());
            int recvdPartialSum = Integer.parseInt(stk.nextToken());

            System.out.println("\n"+recvdProcessID+" "+recvdPartialSum);

            int[] arrayPartialSum = new int[multicastSenderReceiver.numProcesses];              // array to store partial sums

            /* Store each received partial sum in an array of partial 
             sums at index corresponding to the respective */

            arrayPartialSum[recvdProcessID] = recvdPartialSum;

            // For debug, here is another way of listing the elements of the array of partial sums.
            System.out.println("\nHere is the array of partial sums: ");
            for (int element: arrayPartialSum){
                System.out.println("\n"+element);
            }

            // Compute and Display the sum of all the partial sums:
            int grandTotal = 0;
            for (int s: arrayPartialSum) {
                grandTotal += s;
            }
            System.out.println("\nGrand Total: "+grandTotal);

            /*Finding the maximum value in the array of partial sums */
            int maximumSum = 0;
            maximumSum = maximum.Max(arrayPartialSum);
            System.out.println("The Maximum of all partial sums is"+maximumSum);
        }

    }
    catch (Exception e) {
        e.printStackTrace();
    }
}
}

更新:我将一些元素移出了 while(true) 循环，但现在我在编译时遇到了一种新类型的错误。它显示某些行并显示“无法访问的语句”。有什么想法吗？

public void run(){

    try {
        MulticastSocket readSocket = new MulticastSocket(multicastPort);
        readSocket.joinGroup(group);
        int[] arrayPartialSum = new int[multicastSenderReceiver.numProcesses];              // array to store partial sums
        int grandTotal = 0;

        while (true) {
            byte[] recvBuffer = new byte[MAX_MSG_LEN];
            DatagramPacket packet = new DatagramPacket(recvBuffer, recvBuffer.length, group, multicastPort);

            readSocket.receive(packet);

            String rString = new String(packet.getData());
            String message = new String(rString.getBytes()).trim();                             // Process the received message before use here

            StringTokenizer stk = new StringTokenizer(message, ",");

            int recvdProcessID = Integer.parseInt(stk.nextToken());
            int recvdPartialSum = Integer.parseInt(stk.nextToken());

            System.out.println("\n"+recvdProcessID+" "+recvdPartialSum);

            /* Store each received partial sum in an array of partial 
             sums at index corresponding to the respective */
            arrayPartialSum[recvdProcessID] = recvdPartialSum;
        }

        // Compute and Display the sum of all the partial sums:
        for (int s: arrayPartialSum) {
            grandTotal += s;
        }
        System.out.println("\nGrand Total: "+grandTotal);

        /*Finding the maximum value in the array of partial sums */
        int maximumSum = 0;
        maximumSum = maximum.Max(arrayPartialSum);
        System.out.println("The Maximum of all partial sums is"+maximumSum);

        // For debug, here is another way of listing the elements of the array of partial sums.
        System.out.println("\nHere is the array of partial sums: ");
        for (int element: arrayPartialSum){
            System.out.println("\n"+element);
        }

    }
    catch (Exception e) {
        e.printStackTrace();
    }
}

Answer 1

我终于重新审视了我的源代码并理解该代码实际上是功能性的，即好的。可以进行一些调整以使其更漂亮并改进逻辑。例如，我将一些变量声明移出无限 while 循环...

我的问题的答案非常简单:

1. 行arrayPartialSum[recvdProcessID] = recvdPartialSum;实际上做了它应该做的事情。也就是说，将每个接收到的部分和存储在部分和数组中与其进程 ID 对应的索引处。逻辑中的问题实际上不在于代码，而在于我作为程序的用户启动进程的方式。我需要确保在每个进程中按回车键，以便将其部分和发送到多播组。

2. 要检索给定项目的索引，下面的代码可以完成这项工作，maximumSum 是试图在数组 arrayPartialSum 中查找其索引的元素>:

   for (int i = 0; i < arrayPartialSum.length; i++) {
       if (arrayPartialSum[i] == maximumSum) {
           retval = i;
           break;
       }
   }