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我正在尝试用 Java 编写控制台客户端-服务器应用程序；使用套接字，我目前有一个简单的登录系统和一个简单的命令系统。登录系统似乎工作，尽管它向客户端打印“无效的用户名和密码”行，无论用户是否输入正确的凭据。- 连接肯定有效。

但是，命令系统似乎根本不起作用，当服务器收到命令时，它似乎没有发回任何东西。

所以我的主要问题是为什么我的服务器在收到命令时不向客户端发送任何内容？

这是我的服务器：

import java.io.*;
import java.net.*;

class TCPServer2
{
public static void main(String argv[]) throws Exception
{


    ServerSocket welcomeSocket = new ServerSocket(6789);
    String[][] Login = {{"MATT","UNCP"},{"JOHN","UNCP"},{"CARL","UNCP"}};
    String Command;
    String username;
    String username1;
    String password;
    String password1;
    String cmd;
    while(true)
    {
        Socket connectionSocket = welcomeSocket.accept();
        BufferedReader inFromClient =
           new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
        DataOutputStream outToClient = new DataOutputStream(connectionSocket.getOutputStream());
        username = inFromClient.readLine();
        System.out.println("\nUsername received: " + username);
        password = inFromClient.readLine();
        System.out.println("\nPassword received: " + password);
        username1=username.toUpperCase();
        password1=password.toUpperCase();


        for(int i = 0; i<Login.length; i++)
        {
            if(Login[i][0].equals(username1) && Login[i][1].equals(password1))
            {
                outToClient.writeBytes("Hello " + username1);
                outToClient.writeBytes("\nOther users registered on the server currently include: \n");

                for(int k = 0; k<Login.length; k++)
                {
                    outToClient.writeBytes(Login[k][0]);
                    }
            }
            else {
                outToClient.writeBytes("Invalid Username and/or password.\n");
            }
            }
                        BufferedReader inFromClient2 =
           new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
        DataOutputStream outToClient2 = new DataOutputStream(connectionSocket.getOutputStream());
        Command = inFromClient2.readLine();
        System.out.println("\nCommand received: " + Command);


if(Command.equals("listTranslations"))
{
outToClient2.writeBytes("English,Thai,Geordie,etc.");
}
else
{
if(Command.equals("getCost"))
{
outToClient2.writeBytes("£100\n");
}
else
{
outToClient2.writeBytes("Invalid Command");
}
}

}

    }
}

这是我的客户：

import java.io.*;
import java.net.*;

class TCPClient2
{
public static void main(String argv[]) throws Exception
{
     String userName;
     String passWord;
     String loginInfo;
     String loginInfo2;
     String loginInfo3;
     String command;
     String commandInfo;
     String commandInfo2;

     BufferedReader inFromUser = new BufferedReader( new InputStreamReader(System.in));
     Socket clientSocket = new Socket("localhost", 6789);
     DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
     BufferedReader inFromServer = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

     System.out.println("Username: ");
     userName = inFromUser.readLine();
     outToServer.writeBytes(userName + "\n");

     System.out.println("Password: ");
     passWord = inFromUser.readLine();
     outToServer.writeBytes(passWord + "\n");

     loginInfo = inFromServer.readLine();
     System.out.println(loginInfo);
     loginInfo2 = inFromServer.readLine();
     System.out.println(loginInfo2);
     loginInfo3 = inFromServer.readLine();
     System.out.println(loginInfo3);

     System.out.println("Please enter a command: ");
     command = inFromUser.readLine();
     outToServer.writeBytes(command);

     commandInfo = inFromServer.readLine();
     System.out.println(commandInfo);
     commandInfo2 = inFromServer.readLine();
     System.out.println(commandInfo);



     clientSocket.close();
 }
}

这是我第一次在 stackoverflow 上提问，但我过去浏览过很多次。所以我只想对你们提供的伟大社区表示感谢。

4

2 回答 2

0

这是我评论的延续：

我就是这样做的，首先我会用这样String[][] Login = {{"MATT","UNCP"},{"JOHN","UNCP"},{"CARL","UNCP"}};的东西替换它：

Map<String, String> userDetails = new HashMap<String, String>();
userDetails.put("MAT", "UNCP");
userDetails.put("JOHN","UNCP"); 
userDetails.put("CARL", "UNCP");

然后，而不是这个：

 for(int i = 0; i<Login.length; i++)
        {
            if(Login[i][0].equals(username1) && Login[i][1].equals(password1))
            {
                outToClient.writeBytes("Hello " + username1);
                outToClient.writeBytes("\nOther users registered on the server currently include: \n");

                for(int k = 0; k<Login.length; k++)
                {
                    outToClient.writeBytes(Login[k][0]);
                    }
            }
            else {
                outToClient.writeBytes("Invalid Username and/or password.\n");
            }
        }

我会这样做：

if (userDetails.get(username1).equals(password1))
{
    outToClient.writeBytes("Hello " + username1);
                outToClient.writeBytes("\nOther users registered on the server currently include: \n");

    for (String str : userDetails.keySet()
    {
         outToClient.writeBytes(str);
    }

}
else
{
    outToClient.writeBytes("Invalid Username and/or password.\n");
}

我看到它的方式，系统正在工作并打印Invalid credentials字符串是因为，假设您提供这些登录详细信息：CARL并且UNCP，您正在传递第二组凭据，因此您的循环将通过将它们与凭据进行比较来检查凭据第一组，由于它们不匹配，它将打印消息。在第二次迭代中，它将看到凭据匹配并将您登录。

有关更多信息，请查看JavaDoc。HashMap 是一个集合，除了通常的List和Set.

于 2012-05-09T13:23:13.330 回答
0

我不确定这是否会对您有所帮助，但请检查您是否不必在每次 writeBytes 调用后刷新以真正将数据输出到客户端。

尝试添加 outToClient.flush();

于 2012-05-09T13:11:53.300 回答