几天前我已经开始学习 Java 套接字编程。我在某个网站上找到了此代码，用于将文件从服务器传输到多个客户端（多线程，使用线程池）。
当我使用环回接口（127.0.0.1）运行此应用程序时，它工作正常，文件被传输到目标文件夹。但是当我将服务器电脑（192.168.1.2）连接到客户端电脑（192.168.1.3）时，出现异常并说
"Could not establish I/O for IP: <ipaddress of client> <port number>"
客户端和服务器端用网线连接好，互相ping通。他们之间没有防火墙。我对网站和 Java 套接字的初学者非常陌生。
谁能帮我调试或理解错误？
Client Side Code: 2 Java files
myfileclient.java // First File
import java.io.*;
import javax.swing.*;
public class myfileclient {
/**
* @param args
* @throws IOException
* @throws InterruptedException
*/
public static void main(String[] args) throws IOException, InterruptedException {
JFileChooser chooser = new JFileChooser();
chooser.showOpenDialog(null);
File file = chooser.getSelectedFile();
String fileName = file.getName();
//System.out.println("You have selected: " + filename);
String serverAddress= "127.0.0.1";
int serverPort= 4444;
//String fileName = "D:\\a.pdf";
//Create Socket
System.out.println("client >Creating Socket to " + serverAddress + ":" + serverPort);
JOptionPane.showMessageDialog(null,"Client: Connecting to: " + serverAddress + serverPort + "\nClient Connecting....." + "\nClient Requesting file : " + fileName ,"Success",JOptionPane.PLAIN_MESSAGE);
SocketHandling client = new SocketHandling(serverAddress, serverPort);
//Connect
System.out.println("client >Connecting");
client.connect();
//File request
System.out.println("client >Requesting file : " + fileName);
client.requestFile("D:\\a.pdf");
//Close all
System.out.println("client >Close Connection");
client.close();
}
}
SocketHandling.java // Second File
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import javax.swing.JOptionPane;
public class SocketHandling {
private Socket client;
private PrintWriter socketWriter;
private BufferedReader socketReader;
public String destIpAddress;
public int destPort;
public SocketHandling(String destIpAddress, int destPort) {
this.destIpAddress = destIpAddress;
this.destPort = destPort;
}
public void connect() {
try {
//Create socket
client = new Socket(this.destIpAddress,this.destPort);
//Create read/write buffers for socket
socketReader = new BufferedReader(new InputStreamReader(client.getInputStream()));
socketWriter = new PrintWriter(client.getOutputStream(), true);
} catch (UnknownHostException e) {
System.err.println("Unkown host: " + destIpAddress);
} catch (IOException e) {
System.out.println("Could not establish I/O for IP: "+ destIpAddress + " on port: " + destPort);
JOptionPane.showMessageDialog(null,"Could not establish I/O for IP: "+ destIpAddress + " on port: " + destPort,"Error",JOptionPane.PLAIN_MESSAGE);
}
}
public void requestFile(String filename) throws IOException {
//Timers
long start = System.currentTimeMillis();
int bytesRead;
int current = 0;
//Hard coded temporary file size
int filesize=7000000;
//Send File Name to server
socketWriter.println(filename);
socketWriter.flush();
//Get n and m
String message = (String)socketReader.readLine();
//Split string up
String[] tokens = message.split("[,]");
int ConnectionCounter = Integer.parseInt(tokens[0]);
int FileCounter = Integer.parseInt(tokens[1]);
if(FileCounter >= 0){
//File exists
System.out.println("client >File " + filename + " was found at the serve");
System.out.println("client >Server handled " + ConnectionCounter + " requests, " + FileCounter + " request were successsful.");
//Receive file
System.out.println("client >Downloading file " + filename);
byte [] mybytearray = new byte [filesize];
InputStream is = client.getInputStream();
FileOutputStream fos = new FileOutputStream("D:\\copy.pdf"); //Files Added to Download directory
BufferedOutputStream bos = new BufferedOutputStream(fos);
bytesRead = is.read(mybytearray,0,mybytearray.length);
current = bytesRead;
do {
bytesRead =
is.read(mybytearray, current, (mybytearray.length-current));
if(bytesRead >= 0) current += bytesRead;
} while(bytesRead > -1);
bos.write(mybytearray, 0 , current);
bos.flush();
long end = System.currentTimeMillis();
System.out.println("client >Download complete (" + (end-start) + "ms)");
JOptionPane.showMessageDialog(null,"File:" + filename + " was found at the Server\nServer handled " + ConnectionCounter + "requests" + FileCounter + " requests were successsful!!\nDownloading file.....\nDownload complete!! (" + (end-start) + "ms) ","Success",JOptionPane.PLAIN_MESSAGE);
bos.close();
}else{
//Files does not exists
//System.out.println("client >File " + filename + " was not found at the serve");
System.out.println("client >Connection Counter : " + ConnectionCounter + " File Counter : " + FileCounter);
JOptionPane.showMessageDialog(null,"File " + filename + " was not found at the Server ","Error",JOptionPane.PLAIN_MESSAGE);
}
}
public void close() {
try {
//Closes read/write buffers and the socket
socketWriter.close();
socketReader.close();
client.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
服务器端代码：4 个 Java 文件
myfileserver.java // First File
import javax.swing.JOptionPane;
public class myfileserver {
/**
* @param args
*/
public static void main(String[] args) {
System.out.println("Server: Start");
JOptionPane.showMessageDialog(null,"Server Started ","Success",JOptionPane.PLAIN_MESSAGE);
Multithreading server = new Multithreading(4444);
server.run();
}
}
Multithreading.java // Second File
import java.io.IOException;
import java.net.BindException;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class Multithreading implements Runnable{
private ServerSocket server;
private ExecutorService pool;
public Multithreading(int listenPort) {
this.pool = Executors.newFixedThreadPool(50); //Max connections
try {
server = new ServerSocket(listenPort);
} catch (IOException e) {
e.printStackTrace();
}
}
public void run() {
try {
while(true) {
pool.execute(new WorkerThread(server.accept()));
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
ServerStatistics.java // Third File
public class ServerStatistics {
private static int ConnectionCounter; //M
private static int FileCounter; //N
public static synchronized int getConnectionCounter(){
return ConnectionCounter;
}
public static synchronized int getFileCounter(){
return FileCounter;
}
public static synchronized int IncConnectionCounter(){
return ConnectionCounter++;
}
public static synchronized int IncFileCounter(){
return FileCounter++;
}
}
WorkerThread.java // Fourth File
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;
import java.util.LinkedList;
import java.util.List;
import javax.swing.JOptionPane;
public class WorkerThread extends Thread {
public Socket connection;
public WorkerThread(Socket connection) {
this.connection = connection;
handleConnection();
}
private synchronized boolean handleConnection() {
try {
//Increment Connection statistics
ServerStatistics.IncConnectionCounter();
//Create read/write buffers for the socket
PrintWriter streamWriter = new PrintWriter(connection.getOutputStream());
BufferedReader streamReader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
//Get filename from client
String fileName = streamReader.readLine();
System.out.println("server> File " + fileName + " requested from " + connection.getInetAddress().getHostAddress());
try{
File myFile = new File (fileName); //Files Are in the Upload directory
if(myFile.exists()){
//File exists
ServerStatistics.IncFileCounter();
System.out.println("server> Successful, " + fileName + " exists");
System.out.println("server> Total successful requests so far = " + ServerStatistics.getFileCounter() + " out of " + ServerStatistics.getConnectionCounter());
//Send N and M
streamWriter.println(ServerStatistics.getConnectionCounter() + "," + ServerStatistics.getFileCounter());
streamWriter.flush();
//Create File buffer to read file to socket
byte [] mybytearray = new byte [(int)myFile.length()];
FileInputStream fis = new FileInputStream(myFile);
BufferedInputStream bis = new BufferedInputStream(fis);
bis.read(mybytearray,0,mybytearray.length);
OutputStream os = connection.getOutputStream();
//Send File
os.write(mybytearray,0,mybytearray.length);
os.flush();
connection.close();
System.out.println("server> File transfer complete [" + fileName + "]");
JOptionPane.showMessageDialog(null,"File " + fileName + " requested from " + connection.getInetAddress().getHostAddress() +"\nSuccessful File exists!!" +"\nTotal successful requests so far = " + ServerStatistics.getFileCounter() + " out of " + ServerStatistics.getConnectionCounter() + "\nFile transfer complete [" + fileName + "]" ,"",JOptionPane.PLAIN_MESSAGE);
}else{
//File does not exists
System.out.println("server> Not Successful, " + fileName + " does not exists");
System.out.println("server> Total successful requests so far = " + ServerStatistics.getFileCounter() + " out of " + ServerStatistics.getConnectionCounter());
//Send N and -1 b/c file does not exists
streamWriter.println(ServerStatistics.getConnectionCounter() + "," + (-1));
streamWriter.flush();
}
return true;
}catch (Exception e){//Catch exception if any
streamWriter.println(ServerStatistics.getConnectionCounter() + ",-1");
streamWriter.flush();
System.err.println("Error: " + e.getMessage());
return false;
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return false;
}
}
}