客户端套接字不接受来自 cmd 的任何输入

Question

我创建了一个程序，其中服务器向客户端发送文件列表，然后客户端可以请求检查内容。它正确发送文件列表，但客户端不接受来自控制台的任何输入。 这是服务器程序

import java.util.*;
import java.io.*;
import java.net.*;
class TCPServer{
    public static void main(String args[]) throws Exception{
    ServerSocket server = new ServerSocket(4888);
    while(true){
    Socket client = server.accept();
    System.out.println(client);
    DataOutputStream out = new DataOutputStream(client.getOutputStream());
    File path = new File("C://testjava");
    String[] files = path.list();
    String send = "";
    for(String file:files){
        send = send + file + "\n";
    }
    out.writeBytes(send);
    BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream    ()));
    String search_file = in.readLine();
    String searching = "";
    for(String file:files){
        if (file.equals(search_file)){
        searching = search_file;
        }
    }
if(searching.equals("")){
        out.writeBytes("Requested file does not exist");
        client.close();
    }
    Scanner file = new Scanner(new FileReader(searching));
    while(file.hasNextLine()){
        out.writeBytes(file.nextLine());
    }
    client.close();
    }
    }
}

这是客户端程序

import java.util.*;
import java.io.*;
import java.net.*;
class TCPClient{
    public static void main(String args[]) throws Exception{
        Socket client = new Socket("localhost",4888);
        BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
        String  display = ""; 
        while ((display = in.readLine()) != null) {
            System.out.println(display);
        }
        System.out.println("\nChoose a file");
        Scanner src = new Scanner(System.in);
        String ask_file = src.nextLine();
        DataOutputStream out = new DataOutputStream(client.getOutputStream());
        out.writeBytes(ask_file);
        display = ""; 
        while ((display = in.readLine()) != null) {
            System.out.println(display);
        }
    }
}

谁能解释为什么客户端不接受任何输入？ 谢谢

Answer 1

在客户端，in.readLine() 阻塞，直到 Socket 关闭。

由于您显然还不想关闭套接字，您可以让服务器发送一条特殊消息以在循环中匹配 for。匹配时，跳出循环。

此外，类似 readLine/nextLine 的方法会占用换行符，因此您需要像 @EJP 所说的那样添加一些。我在下面编辑了您的代码。我测试了它，它现在似乎可以工作了。

TCP服务器

import java.util.*;
import java.io.*;
import java.net.*;
class TCPServer{
    public static void main(String args[]) throws Exception{
    ServerSocket server = new ServerSocket(4888);
    while(true){
    Socket client = server.accept();
    System.out.println(client);
    DataOutputStream out = new DataOutputStream(client.getOutputStream());
    File path = new File("C://Users/Brian/Desktop");
    String[] files = path.list();
    String send = "";
    for(String file:files){
        send = send + file + "\n";
    }
    send = send + "END\n"; // ADD SOMETHING LIKE THIS ------------------------------>
    out.writeBytes(send);
    BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream    ()));
    String search_file = in.readLine();
    String searching = "";
    for(String file:files){
        if (file.equals(search_file)){
        searching = search_file;
        }
    }
if(searching.equals("")){
        out.writeBytes("Requested file does not exist");
        client.close();
    }
    Scanner file = new Scanner(new FileReader(searching));
    while(file.hasNextLine()){
        out.writeBytes(file.nextLine() + "\n"); // ADD A NEWLINE HERE ------------------>
    }
    client.close();
    }
    }
}

TCP客户端

import java.util.*;
import java.io.*;
import java.net.*;
class TCPClient{
    public static void main(String args[]) throws Exception{
        Socket client = new Socket("localhost",4888);
        BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
        String  display = ""; 
        // ADD A TEST FOR "END" HERE --------------------------------------------->
        while ((display = in.readLine()) != null && !display.equals("END")) {
            System.out.println(display);
        }
        System.out.println("\nChoose a file");
        Scanner src = new Scanner(System.in);
        String ask_file = src.nextLine() + "\n"; // ADD A NEWLINE HERE ----------->
        DataOutputStream out = new DataOutputStream(client.getOutputStream());
        out.writeBytes(ask_file);
        display = ""; 
        while ((display = in.readLine()) != null) {
            System.out.println(display);
        }
    }
}

Answer 2

你在读行，但不是在写行。您需要在使用writeBytes() 编写的字符串中添加\n。否则readLine() 将永远阻塞等待永远不会到达的行终止符。