我是 Java 的初学者，也是套接字编程的初学者。
我编写的这个程序旨在允许客户端和服务器之间的 p2p 文件同步。
当一个对等体与另一个对等体建立 TCP 连接时，他们都会比较他们拥有的文件列表并继续交换文件，以便他们拥有完全相同的文件。TCP 连接必须保持打开状态，直到在连接的任一端手动终止对等进程。
我查看了在线教程和类似程序来编写该程序的代码。但是，运行服务器后，当我运行客户端时，控制台上会显示以下错误。
IOException: java.net.ConnectException: Connection timed out: connect
请告诉我如何解决该错误。提前非常感谢！
这是我的代码供参考。
服务器：
package bdn;
import java.net.*;
import java.io.*;
import java.util.*;
public class MultipleSocketServer extends Thread{
// private Socket connection;
private String TimeStamp;
private int ID;
static int port = 6789;
static ArrayList<File> currentfiles = new ArrayList<File>();
static ArrayList<File> missingsourcefiles = new ArrayList<File>();
public static void main(String[] args)
{
File allFiles = new File("src/bdn/files");
if (!allFiles.exists()) {
if (allFiles.mkdir()) {
System.out.println("Directory is created.");
}
}
//Load the list of files in the directory
listOfFiles(allFiles);
try {
new MultipleSocketServer().startServer();
} catch (Exception e) {
System.out.println("I/O failure: " + e.getMessage());
e.printStackTrace();
}
}
public static void listOfFiles(final File folder){
for (final File fileEntry : folder.listFiles()) {
if (fileEntry.isDirectory()) {
listOfFiles(fileEntry);
} else {
//System.out.println(fileEntry.getName());
currentfiles.add(fileEntry.getAbsoluteFile());
}
}
}
public void startServer() throws Exception {
ServerSocket serverSocket = null;
boolean listening = true;
try {
serverSocket = new ServerSocket(port);
} catch (IOException e) {
System.err.println("Could not listen on port: " + port);
System.exit(-1);
}
while (listening) {
handleClientRequest(serverSocket);
}
//serverSocket.close();
}
private void handleClientRequest(ServerSocket serverSocket) {
try {
new ConnectionRequestHandler(serverSocket.accept()).run();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* Handles client connection requests.
*/
public class ConnectionRequestHandler implements Runnable{
private Socket _socket = null;
public ConnectionRequestHandler(Socket socket) {
_socket = socket;
}
public void run() {
System.out.println("Client connected to socket: " + _socket.toString());
try {
ObjectOutputStream oos = new ObjectOutputStream (_socket.getOutputStream());
oos.flush();
oos.writeObject(currentfiles); //sending to client side.
oos.flush();
} catch (IOException e) {
e.printStackTrace();
}
syncMissingFiles();
}
@SuppressWarnings("unchecked")
public void syncMissingFiles(){
try {
ObjectInputStream ois = new ObjectInputStream(_socket.getInputStream());
System.out.println("Is the socket connected="+_socket.isConnected());
missingsourcefiles= (ArrayList<File>) ois.readObject();
System.out.println(missingsourcefiles);
//add missing files to current file list.
ListIterator<File> iter = missingsourcefiles.listIterator();
File temp_file;
while (iter.hasNext()) {
// System.out.println(iter.next());
temp_file = iter.next();
currentfiles.add(temp_file);
}
} catch (IOException e) {
e.printStackTrace();
} catch ( ClassNotFoundException e) {
e.printStackTrace();
}
}
}
}
客户：
package bdn;
import java.net.*;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.ListIterator;
/* The java.io package contains the basics needed for IO operations. */
import java.io.*;
public class SocketClient {
/** Define a port */
static int port = 2000;
static Socket peer_socket = null;
static String peerAddress;
static ArrayList<File> currentfiles = new ArrayList<File>();
static ArrayList<File> sourcefiles = new ArrayList<File>();
static ArrayList<File> missingsourcefiles = new ArrayList<File>();
static ArrayList<File> missingcurrentfiles = new ArrayList<File>();
SocketClient(){}
public static void listOfFiles(final File folder) {
for (final File fileEntry : folder.listFiles()) {
if (fileEntry.isDirectory()) {
listOfFiles(fileEntry);
} else {
//System.out.println(fileEntry.getName());
currentfiles.add(fileEntry.getAbsoluteFile());
}
}
}
@SuppressWarnings("unchecked")
public static void getListfromPeer() {
try {
ObjectInputStream inList =new ObjectInputStream(peer_socket.getInputStream());
sourcefiles = (ArrayList<File>) inList.readObject();
} catch (ClassNotFoundException e) {
System.err.println("Error in data type.");
}catch (IOException classNot){
System.err.println("Error in data type.");
}
}
public static void compareList1() {
//Compare the source files and current files. If not in current files, add the files to "missingcurrentfiles".
ListIterator<File> iter = sourcefiles.listIterator();
File temp_file;
while (iter.hasNext()) {
// System.out.println(iter.next());
temp_file = iter.next();
if (!currentfiles.contains(temp_file)) //file cannot be found
{
missingcurrentfiles.add(temp_file);
}
}
}
public static void compareList2() {
//Compare the source files and current files. If not in current files, add the files to "missingsourcefiles".
ListIterator<File> iter = currentfiles.listIterator();
File temp_file;
while (iter.hasNext()) {
// System.out.println(iter.next());
temp_file = iter.next();
if (!sourcefiles.contains(temp_file)) //file cannot be found
{
missingsourcefiles.add(temp_file);
}
}
}
public static void main(String[] args) {
//Make file lists of the directory in here.
File allFiles = new File("src/bdn/files");
if (!allFiles.exists()) {
if (allFiles.mkdir()) {
System.out.println("Directory is created.");
}
}
/*Get the list of files in that directory and store the names in array*/
listOfFiles(allFiles);
/*Connect to peer*/
try {
new SocketClient().transfer();
//new TcpClient().checkForInput();
} catch (Exception e) {
System.out.println("Failed at main" + e.getMessage());
e.printStackTrace();
}
}
public void transfer(){
getPeerAddress();
// StringBuffer instr = new StringBuffer();
// String TimeStamp;
try {
/** Obtain an address object of the server */
// InetAddress address = InetAddress.getByName(host);
// System.out.println("Address of connected host:"+ address);
/** Establish a socket connection */
Socket connection = new Socket(peerAddress, port);
System.out.println("New SocketClient initialized");
getListfromPeer();
compareList1();
compareList2();
System.out.println(missingcurrentfiles);
System.out.println(missingsourcefiles);
/** Instantiate a BufferedOutputStream object */
// BufferedOutputStream bos = new BufferedOutputStream(connection.getOutputStream());
/** Instantiate an ObjectOutputStream*/
ObjectOutputStream oos = new ObjectOutputStream(connection.getOutputStream());
oos.flush();
/*
TimeStamp = new java.util.Date().toString();
String process = "Calling the Socket Server on "+ host + " port " + port +
" at " + TimeStamp + (char) 13;
*//** Write across the socket connection and flush the buffer *//*
oos.writeObject(process);
oos.flush();*/
oos.writeObject(missingsourcefiles);
oos.flush();
System.out.println("Missing files in source sent back.");
}
catch (IOException f) {
System.out.println("IOException: " + f);
}
catch (Exception g) {
System.out.println("Exception: " + g);
}
}
public void syncMissingFiles(){
//add missing files to current file list.
ListIterator<File> iter = missingcurrentfiles.listIterator();
File temp_file;
while (iter.hasNext()) {
// System.out.println(iter.next());
temp_file = iter.next();
currentfiles.add(temp_file);
}
}
public static void getPeerAddress() {
// prompt the user to enter the client's address
System.out.print("Please enter the IP address of the client :");
// open up standard input
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
// read the IP address from the command-line
try {
peerAddress = br.readLine();
} catch (IOException ioe) {
System.out.println("IO error trying to read client's IP address!");
System.exit(1);
}
System.out.println("Thanks for the client's IP address, " + peerAddress);
}
}