Java IPC w/Sockets - 使用环回设备

Posted 2023-02-16

【中文标题】Java IPC w/Sockets - 使用环回设备

【英文标题】：Java IPC w/Sockets - Using Loopback Device

【发布时间】：2015-11-23 21:39:50

【问题描述】：

所以我试图在一个项目的进程之间实现套接字通信。但我似乎无法通过环回设备连接到任何端口。我在这里错过了什么吗？我让这个尝试在近 500 个端口上运行，但它总是拒绝连接。

static final String HOST = "127.0.0.1";

public static void main(String[] args) throws IOException 
    int port = 1000;
    while (true) 
        try 
            socket = new Socket(HOST, PORT); // initialing the socket
            writer = new OutputStreamWriter(socket.getOutputStream());
            reader = new InputStreamReader(socket.getInputStream());
            break;
         catch (ConnectException ex) 
            System.out.println("failure on port: " + port);
            ++port; // increment port to try next 
        
    

    ...

;

如果有人想看声明什么的，这里是整个程序。

package socket_ipc;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.InputStreamReader;
import java.net.ConnectException;
import java.net.Socket;

public class Socket_IPC 
    static final int NUMBER_OF_MESSAGES = 100; // number of messages to pass
    static int[] PRODUCED_MSSG = new int[NUMBER_OF_MESSAGES]; // for comparing
    static int[] CONSUMED_MSSG = new int[NUMBER_OF_MESSAGES]; // for comparing

    static final String HOST = "127.0.0.1";    // IP address of loopback device
    static final int PORT = 1000;              // arbitrary port number (local)

    static OutputStreamWriter writer;   // write to socket
    static InputStreamReader reader;    // read from socket
    static Socket socket;               // the socket

    private static class s_Producer extends Thread 
        @Override
        public void run() 
            for (int i = 0; i < NUMBER_OF_MESSAGES; i++) 
                try 
                    PRODUCED_MSSG[i] = (int)(Math.random() * 256); // get data
                    writer.write(PRODUCED_MSSG[i]); // write data to the socket
                 catch (IOException ex) 
                    System.err.println(ex.toString());
                
            
        
    

    private static class s_Consumer extends Thread 
        @Override
        public void run() 
            for(int i = 0; i < NUMBER_OF_MESSAGES; i++) 
                try 
                    int data = reader.read();   // obtain data from the socket
                    CONSUMED_MSSG[i] = data;    // put retrieved data in array
                 catch (IOException ex) 
                    System.err.println(ex.toString());
                
            
        
    

    public static void main(String[] args) throws IOException 
        int port = PORT; // beginning at 1000
        while (true) 
            try 
                socket = new Socket(HOST, port); // initialing the socket
                writer = new OutputStreamWriter(socket.getOutputStream());
                reader = new InputStreamReader(socket.getInputStream());
                break;
             catch (ConnectException ex) 
                System.out.println("failure on port: " + port);
                ++port; // increment port to try next 
            
        

        /* insanciating and starting the producer process */
        s_Producer p = new s_Producer();
        p.start();

        /* insanciating and starting the consumer process */
        s_Consumer c = new s_Consumer();
        c.start();

        try  /* joining threads to wait for completion */
            p.join();
            c.join();
         catch (InterruptedException ex) 
            System.err.println(ex.toString());
        

        for (int i = 0; i < NUMBER_OF_MESSAGES; i++) 
            System.out.println(
                "[" + i + "]: " + PRODUCED_MSSG[i] + " == " + CONSUMED_MSSG[i]);
            if (PRODUCED_MSSG[i] != CONSUMED_MSSG[i]) 
                System.out.println("PROCESS SYNCHRONIZATION ERROR!");
            System.exit(0);
            
        

        System.out.println("PROCESS SYNCHRONIZATION SUCCESS!");

    

;

【问题讨论】：

在您尝试连接的端口上是否有任何监听？

我建议您尝试连接到已经有服务运行的端口。如果您打印实际错误，它应该说“连接被拒绝”，告诉您没有在该端口上监听。

那么当我在该端口上创建套接字时，我没有让套接字监听吗？

我建议the Oracle Java tutorial on networking and specifically client-server and sockets? 它非常全面，显示了客户端和服务器对。

【参考方案1】：

好吧，我不确定问题的确切原因，很可能是使用了 DataInputStream 类。这些通过提供基于对象的特定读写操作提供了一个更简单的解决方案；比如dis.readInt()和dos.writeInt(int n)。

这里是完整并成功运行的源代码：

package socket_ipc;
import java.net.*;
import java.io.*;
/** Socket Inter-Process Communication.
 * Implements the Producer-Consumer Problem, using Sockets for IPC.
 * @author William Hatfield: CEG-4350-01 Fall 2015
 */
public class Socket_IPC 
    static final int NUMBER_OF_MESSAGES = 100; // number of messages to pass
    static int[] PRODUCED_MSSG = new int[NUMBER_OF_MESSAGES]; // for comparing
    static int[] CONSUMED_MSSG = new int[NUMBER_OF_MESSAGES]; // for comparing
    static final String HOST = "127.0.0.1"; // IP address of loopback device
    static final int PORT = 1234;           // arbitrary port number (local)
    static ServerSocket serverSocket;       // the shared server socket
    private static class Producer extends Thread 
        @Override
        public void run() 
            try 
                Socket toClient = serverSocket.accept();
                DataOutputStream dos = new DataOutputStream(toClient.getOutputStream());
                for (int i = 0; i < NUMBER_OF_MESSAGES; i++) 
                PRODUCED_MSSG[i] = 
                        (int)((Math.random() - .5) * Integer.MAX_VALUE);
                dos.writeInt(PRODUCED_MSSG[i]);
            
             catch (IOException ex) 
                System.err.println("Producer Error: " + ex.toString());
            
        
    
    private static class Consumer extends Thread 
        @Override
        public void run() 
            try 
                Socket fromServer = new Socket(HOST, PORT);
                DataInputStream dis = new DataInputStream(fromServer.getInputStream());
                for (int i = 0; i < NUMBER_OF_MESSAGES; i++) 
                CONSUMED_MSSG[i] = dis.readInt();
            
             catch (IOException ex) 
                System.err.println("Consumer Error: " + ex.toString());
                
        
    
    public static void main(String[] args) 
        try 
            serverSocket = new ServerSocket(PORT);
            Producer p = new Producer();    // create the producer thread
            Consumer c = new Consumer();    // create the consumer thread
            p.start();                      // start the producer thread
            c.start();                      // start the consumer thread
            p.join();                       // wait for producer thread
            c.join();                       // wait for consumer thread
         catch (InterruptedException | IOException ex)  /* handle later */ 
         /* compare produced and consumed data, exit if any match fails */
        for (int i = 0; i < NUMBER_OF_MESSAGES; i++) 
            System.out.print("[" + i + "]: " + PRODUCED_MSSG[i]);
            System.out.println(" == " + CONSUMED_MSSG[i]);
            if (PRODUCED_MSSG[i] != CONSUMED_MSSG[i]) 
                System.out.println("PROCESS SYNC ERROR AT INDEX: " + i);
                System.exit(0);
            
        
        /* inform the user that synchroniozation was succesful, then exit */
        System.out.println("SYNC SUCCESFUL!");
    

如果您有任何改进意见，我很乐意倾听。尤其是对于顽固的 Java 程序员来说，我敢肯定这里有些东西违背了标准的 Java 实践！

【讨论】：

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