我已经尝试过所有事情，而且我已经结束了。我正在编写一个简单的文件服务器，让用户telnet，提供用户名并搜索给该用户的访问级别，然后显示文件列表，只允许他们查看文件的内容有足够的访问级别。这段代码用于服务器端，我只是为客户端使用PuTTY。
第一次运行按预期工作，
What is your username? paul
Filename:Access Level
chemistryhomework.txt:5
messageforbob.txt:0
nuclearlaunchcodes.txt:10
Which file would you like to read?
nuclearlaunchcodes.txt
The launch password is "UnlimitedBreadsticks"
然后我关闭PuTTY并再次尝试，并获得此
Filename:Access Level
chemistryhomework.txt:5
messageforbob.txt:0
nuclearlaunchcodes.txt:10
Which file would you like to read?
什么时候应该从头开始并询问我的用户名。第三次尝试，它显示一个空行并在几秒钟后断开连接。
包含所有文件名及其访问级别的文件如下所示：
chemistryhomework.txt:5
nuclearlaunchcodes.txt:10
messageforbob.txt:0
我认为它可能在这里的某个地方
//show list of files
int fileaccess;
outToClient.writeBytes("\n\rFilename:Access Level \n \r");
for (Entry<String, Integer> entry : files.entrySet()) //show all files and access levels
{
String key = entry.getKey();
Integer value = entry.getValue();
outToClient.writeBytes(key + ":" + value + "\n \r");
}
while(!check)
{
//ask user for file to read
outToClient.writeBytes("Which file would you like to read? \n \r");
String filetoread = inFromClient.readLine();
try
{
fileaccess = files.get(filetoread); //get access level requirement of file
if (fileaccess > accesslevel) //if user is lacking the access level
{
outToClient.writeBytes("Error: You do not have sufficient privileges to access this file! \n \r");
welcomeSocket.close();
connectionSocket.close();
}
else
{
try //try to read the file, if it exists. Just a backup verification
{
file = new File(filetoread);
Scanner scannerfile = new Scanner(file);
while (scannerfile.hasNextLine())
{
String line = scannerfile.nextLine();
line=line.trim();
outToClient.writeBytes(line + "\n\r");
}
outToClient.writeBytes("\n\r");
scannerfile.close();
}
catch (FileNotFoundException e)
{
outToClient.writeBytes("File not found! \n \r");
}
check = true;
}
}
catch (NullPointerException e) //first line of defense for checking made-up files
{
outToClient.writeBytes("Error: File does not exist! \n \r");
}
}
check = true;
//outToClient.writeBytes("Press enter to terminate session"); //user can see contents of file just in case disconnecting
//inFromClient.readLine(); //closes the window (like PuTTY)
inFromClient.close();
outToClient.close();
welcomeSocket.close();
connectionSocket.close();
但这是我的代码，完整的。我通过关闭所有东西来徒劳地试图修复它。
package server;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
import java.io.*;
import java.net.*;
import static java.lang.System.out;
public class Server
{
static Map<String, Integer> files = new HashMap<String, Integer>(); //contains file names and the access level required to open them
static Map<String, Integer> users = new HashMap<String, Integer>(); //contains user names and the access level assigned to them
public static void main(String[] args) throws IOException
{
out.println("Starting server...");
//read datafile.txt into files hashmap
File file = new File("datafile.txt");
try
{
out.println("Reading datafile.txt");
Scanner scannerdata = new Scanner(file);
while (scannerdata.hasNextLine())
{
String line = scannerdata.nextLine();
line.trim();
String field[] = line.split(":");
files.put(field[0], Integer.parseInt(field[1]));
}
scannerdata.close();
}
catch (FileNotFoundException e)
{
out.println("datafile.txt not found!");
}
////////debug////////////
//for (Entry<String, Integer> entry : files.entrySet())
//{
// String key = entry.getKey();
// Integer value = entry.getValue();
// out.println(key);
// out.println(value);
//}
//int debugclearance = files.get("nuclearlaunchcodes.txt");
//out.println(debugclearance);
////////debug////////////
//read userfile.txt into users hashmap
file = new File("userfile.txt");
try
{
out.println("Reading userfile.txt");
Scanner scannerusers = new Scanner(file);
while (scannerusers.hasNextLine())
{
String line = scannerusers.nextLine();
line.trim();
String field[] = line.split(":");
users.put(field[0], Integer.parseInt(field[1]));
}
scannerusers.close();
}
catch (FileNotFoundException e)
{
out.println("userfile.txt not found!");
}
////////debug////////////
//for (Entry<String, Integer> entry : users.entrySet())
//{
// String key = entry.getKey();
// Integer value = entry.getValue();
// out.println(key);
// out.println(value);
//}
//int debugclearance = users.get("paul");
//out.println(debugclearance);
////////debug////////////
String clientinput;
boolean check = false;
int accesslevel = 0;
while(true)
{
ServerSocket welcomeSocket = null;
Socket connectionSocket = null;
BufferedReader inFromClient = null;
DataOutputStream outToClient = null;
try
{
//start connection
//ServerSocket welcomeSocket = new ServerSocket(19000);
//Socket connectionSocket = welcomeSocket.accept();
welcomeSocket = new ServerSocket(19000);
connectionSocket = welcomeSocket.accept();
//BufferedReader inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
//DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
inFromClient = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
outToClient = new DataOutputStream(connectionSocket.getOutputStream());
while(!check) //authenticate user
{
outToClient.writeBytes("What is your username?");
outToClient.writeBytes(" ");
String username = inFromClient.readLine();
//alternate method I tried
//if(users.get(username) == null)
//{
// outToClient.writeBytes("Invalid username");
//}
//else
//{
// check = true;
//}
try
{
accesslevel = users.get(username);
check = true;
}
catch(NullPointerException e)
{
outToClient.writeBytes("Incorrect username \n \r");
welcomeSocket.close();
connectionSocket.close();
}
}
check = false;
//debug
//outToClient.writeBytes("It worked!");
//outToClient.writeBytes(clientinput);
//show list of files
int fileaccess;
outToClient.writeBytes("\n\rFilename:Access Level \n \r");
for (Entry<String, Integer> entry : files.entrySet()) //show all files and access levels
{
String key = entry.getKey();
Integer value = entry.getValue();
outToClient.writeBytes(key + ":" + value + "\n \r");
}
while(!check)
{
//ask user for file to read
outToClient.writeBytes("Which file would you like to read? \n \r");
String filetoread = inFromClient.readLine();
try
{
fileaccess = files.get(filetoread); //get access level requirement of file
if (fileaccess > accesslevel) //if user is lacking the access level
{
outToClient.writeBytes("Error: You do not have sufficient privileges to access this file! \n \r");
welcomeSocket.close();
connectionSocket.close();
}
else
{
try //try to read the file, if it exists. Just a backup verification
{
file = new File(filetoread);
Scanner scannerfile = new Scanner(file);
while (scannerfile.hasNextLine())
{
String line = scannerfile.nextLine();
line=line.trim();
outToClient.writeBytes(line + "\n\r");
}
outToClient.writeBytes("\n\r");
scannerfile.close();
}
catch (FileNotFoundException e)
{
outToClient.writeBytes("File not found! \n \r");
}
check = true;
}
}
catch (NullPointerException e) //first line of defense for checking made-up files
{
outToClient.writeBytes("Error: File does not exist! \n \r");
}
}
check = true;
//outToClient.writeBytes("Press enter to terminate session"); //user can see contents of file just in case disconnecting
//inFromClient.readLine(); //closes the window (like PuTTY)
inFromClient.close();
outToClient.close();
welcomeSocket.close();
connectionSocket.close();
}
catch(IOException e)
{
//out.println("Connection to client lost");
inFromClient.close();
outToClient.close();
welcomeSocket.close();
connectionSocket.close();
}
inFromClient.close();
outToClient.close();
welcomeSocket.close();
connectionSocket.close();
}
}
}
答案 0 :(得分：0)
这是因为你继续使用相同的套接字。另外我认为您希望支持多线程的多个连接。也许你可以看看这个答案？
Creating a socket server which allows multiple connections via threads and Java
我认为这会让你朝着正确的方向前进。
答案 1 :(得分：0)
您对变量'check'管理不善。您将其设置为true以退出循环，并跳过身份验证过程。尝试对这些部分使用两个不同的变量来避免这种混淆。