Kotlin BufferedReader.readLine() 导致死循环

Question

我正在使用 Kotlin 制作简单的客户端-服务器应用程序。我遇到了 BufferedReader.readLine() 的问题。我的服务器发送了几行文本，在读取它们后，BufferedReader 阻止了程序，因此它不会继续。看起来它还在等待输入。我不知道如何解决它。这是我的客户代码：

package Client

import java.io.BufferedReader
import java.io.IOException
import java.io.InputStreamReader
import java.io.PrintWriter
import java.net.Socket

class ConnectionHandler(client : Socket) {
    private val reader : BufferedReader = BufferedReader(InputStreamReader(client.getInputStream()))
    private val writer : PrintWriter = PrintWriter(client.getOutputStream(), true)
    private var running : Boolean = false

    fun handle() {
        running = true
        while (running) {
            read()
            write()
        }
    }

    private fun write(){
        var intput: String? = readLine()
        if (intput != null) {
            writer.println(intput)
            if(intput.toLowerCase() == "exit")
               running = false
        }
    }

    private fun read(){
        var output : String? = "Server:"

        while (output != null) {
            println(output)
            output = reader.readLine()
        }
    }
}

这是我的服务器代码：

package Server

import java.io.BufferedReader
import java.io.InputStreamReader
import java.io.PrintWriter
import java.net.Socket


class ClientHandler(private val client : Socket) {
    private val reader : BufferedReader = client.getInputStream().bufferedReader()
    private val writer : PrintWriter = PrintWriter(client.getOutputStream(), true)
    private var running : Boolean = false

    fun handle(){
        running = true
        writer.println("Welcome to Server")
        writer.println("Possible operations: + - / *")
        writer.println("Example input 1 + 2 (notice the spaces between signs)")
        writer.println("To Exit write EXIT")


        while (running){
            try {
                val text = reader.readLine()
                if (text.toLowerCase() == "exit"){
                    shutdown()
                    continue
                }
                val values = text.split(" ")
                val result = Calculator().calculate(values[0].toInt(), values[2].toInt(), values[1])
                writer.println(" = $result" )
            }catch (ex: Exception){
                writer.println("Something went wrong, need to exit")
                shutdown()
            }
        }

    }

    private fun shutdown(){
        running = false;
        writer.println("exit")
        client.close()
        println("${client.inetAddress.hostAddress} closed connection")
    }

}

客户端读取最后一行 "To Exit write EXIT" 然后等待，发送接受输入。

Answer 1

readLine()会阻塞等待输入，returnnull只会在socket关闭的时候才阻塞。您需要调整 client/server 通信协议，以便服务器在完成写入后发送一个特殊标记，并且客户端在收到该标记时退出 read 函数中的循环。

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