JAVA TCP 客户端-服务器连接

Question

当我运行这个程序时，客户端类提示用户输入命令，该命令应该转到服务器类并打开一个文件并读取该文件的每一行并将字节长度返回给客户端类以被显示。

不幸的是，一旦我输入命令，什么也没有发生&不知道为什么。

TCP 客户端类

package TcpClient;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.Socket;
import java.io.*;

public class TcpClient {
  public static void main(String[] args) {
    String temp;
    String displayBytes;
    try {
      //create input stream
      BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
      //create client socket, connect to server
      Socket clientSocket = new Socket("localhost",5555);
      //create output stream attached to socket
      DataOutputStream outToServer =
      new DataOutputStream(clientSocket.getOutputStream());

      System.out.print("Command : ");

      //create input stream attached to socket
      BufferedReader inFromServer =
      new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

      temp = inFromUser.readLine();

      //send line to server
      outToServer.writeBytes(temp);

      //read line from server
      //displayBytes = inFromServer.readLine();

      while((displayBytes = inFromServer.readLine()) != null) {
        System.out.print(displayBytes);
      }
      //clientSocket.close();
    }
    catch(Exception ex) {
    }
  }
}

TCP 服务器类

package TcpServer;

import java.io.BufferedReader;
import java.io.*;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;

public class TcpServer {
  public static void main(String[] args) {
    // The name of the file to open.
    String fileName = "input.txt";
    // This will reference one line at a time
    String line = null;
    String holder=null;
    String clientWord;
    int bytNumber;

    try {
      //create welcoming socket at port 5555
      ServerSocket welcomeSocket = new ServerSocket(5555);
      //wait, on welcoming socket for contact by client
      Socket connectionSocket = welcomeSocket.accept();
      //create input stream, attached to socket
      BufferedReader inFromClient = 
      new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
      //create output stream, attached to socket
      DataOutputStream outToClient =
      new DataOutputStream(connectionSocket.getOutputStream());
      //read in line from socket
      clientWord = inFromClient.readLine();

      if(clientWord.equals("query")) {
        try {
          // FileReader reads text files in the default encoding.
          FileReader fileReader = new FileReader(fileName);

          // Always wrap FileReader in BufferedReader.
          BufferedReader buffer = new BufferedReader(fileReader);

          while((line = buffer.readLine()) != null) {
            System.out.println(line);
            bytNumber = line.getBytes().length;
            holder=Integer.toString(bytNumber);
            //pr.println(bytNumber);//only printing first line not going until eof
            outToClient.writeBytes(holder);
            // line = buffer.readLine();
            // pr.flush();
          }   

          // Always close files.
          buffer.close();         
        }
        catch(FileNotFoundException ex) {
          System.out.println("Unable to open file '" + fileName + "'");
        }
        catch(IOException ex) {
          System.out.println ("Error reading file '" + fileName + "'");
          // Or we could just do this: 
          // ex.printStackTrace();
        }
      }// end if statement
    }
    catch(Exception ex) {
    }
  }
}

Answer 1

我建议您只在两侧使用 DataOutputStream 和 DataInputStream 而不要使用 BufferedInputStream。下面稍微修改的代码能够正确地将消息从客户端发送到服务器。现在您可以轻松地让它为您想要实现的目标工作。

服务器

import java.io.BufferedReader;
import java.io.*;
import java.io.InputStreamReader;
import java.net.ServerSocket;
import java.net.Socket;



public class TcpServer {


public static void main(String[] args) {
    // The name of the file to open.
    String fileName = "input.txt";
    // This will reference one line at a time
    String line = null;
    String holder=null;
    String clientWord;
    int bytNumber;

    try
    {
        //create welcoming socket at port 5555
        ServerSocket welcomeSocket = new ServerSocket(5555);
        //wait, on welcoming socket for contact by client
        Socket connectionSocket = welcomeSocket.accept();
        //create input stream, attached to socket
        DataInputStream inFromClient =
                new DataInputStream(connectionSocket.getInputStream());
        //create output stream, attached to socket
        DataOutputStream outToClient =
                new DataOutputStream(connectionSocket.getOutputStream());
        //read in line from socket
        clientWord = inFromClient.readUTF();
    System.out.println(clientWord);

        if(clientWord.equals("query"))
        {


            try 
            {
         // FileReader reads text files in the default encoding.
         FileReader fileReader = new FileReader(fileName);


         // Always wrap FileReader in BufferedReader.
         BufferedReader buffer = new BufferedReader(fileReader);


                while((line = buffer.readLine()) != null) 
                {
             System.out.println(line);
             bytNumber = line.getBytes().length;
             holder=Integer.toString(bytNumber);
             //pr.println(bytNumber);//only printing first line not going until eof
            outToClient.writeBytes(holder);
             // line = buffer.readLine();
            // pr.flush();
                }   

         // Always close files.
         buffer.close();         
            }
            catch(FileNotFoundException ex) 
            {
         System.out.println(
             "Unable to open file '" + 
             fileName + "'");                
            }
            catch(IOException ex) 
            {
         System.out.println(
             "Error reading file '" 
             + fileName + "'");                  
         // Or we could just do this: 
         // ex.printStackTrace();
            }

        }// end if statement
    }

  catch(Exception ex)
    {

    }
}

}

客户端

import java.io.BufferedReader;
  import java.io.InputStreamReader;
  import java.net.Socket;
  import java.io.*;


  public class TcpClient {


       public static void main(String[] args) {
         String temp;
         String displayBytes;
        try
        {
        //create input stream
        BufferedReader inFromUser = new BufferedReader(new InputStreamReader(System.in));
        //create client socket, connect to server
        Socket clientSocket = new Socket("localhost",5555);
        //create output stream attached to socket
        DataOutputStream outToServer =
                new DataOutputStream(clientSocket.getOutputStream());



        System.out.print("Command : ");

        //create input stream attached to socket
        DataInputStream inFromServer = new DataInputStream(clientSocket.getInputStream());

        temp = inFromUser.readLine();

        //send line to server
        //outToServer.writeBytes(temp);
        outToServer.writeUTF(temp);
        outToServer.flush();


       //read line from server
        //displayBytes = inFromServer.readLine();

        while((displayBytes = inFromServer.readUTF()) != null)
        {
        System.out.print(displayBytes);
        }
        //clientSocket.close();
    }
    catch(Exception ex)
    {

    }
}
}