socket編程練習掛了？

Question

我創建了一個非常簡單的 HTTP 代理服務器和后端服務器，可以生成簡單的請求。

代理服務器

package ch2.networking

import java.io.{BufferedReader, InputStreamReader}
import java.net.{ServerSocket, Socket}

class ProxyServer(address: String, port: Int, proxyPort: Int) {
  val proxySocket = new ServerSocket(proxyPort)

  while (true) {
    println("Proxy accepting connections...")
    val connectionSocket = proxySocket.accept()
    println(s"Proxy Accepted Connection: $connectionSocket")

    val connectionInputStream = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream))

    val serverSocket = new Socket(address, port)
    val serverInputStream = new BufferedReader(new InputStreamReader(serverSocket.getInputStream))

    val message: String = connectionInputStream.readLine()
    println(s"Proxy server received: $message")
    serverSocket.getOutputStream.write(message.getBytes("UTF-8"))

    val response = serverInputStream.readLine()
    println(s"Proxy server received $response from server")
    connectionSocket.getOutputStream.write(response.getBytes("UTF-8"))
  }
}

網絡服務器

package ch2.networking

import java.io.{BufferedReader, InputStreamReader}
import java.net.ServerSocket

class Server(port: Int) {
  val socket = new ServerSocket(port)

  while (true) {
    println("Server accepting connections...")
    val connectionSocket = socket.accept()
    println(s"Server Accepted Connection: $connectionSocket")
    val inputStream = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream))
    val request = inputStream.readLine()
    println(s"Received: $request")
    val response =
      """
        |HTTP/1.1 200 OK
        |
        |
        |Yay you win
        |""".stripMargin
    connectionSocket.getOutputStream.write(response.getBytes("UTF-8"))
  }
}

代理收到消息，但隨后對 Web 服務器的寫入永遠掛起。 我做錯了什么？

Answer 1

這是一個有效的實現：

import java.io.InputStream
import java.net.{ServerSocket, Socket}

import scala.annotation.tailrec

trait InputReader {
  @tailrec
  final def readRecur(in: InputStream, sb: StringBuilder = new StringBuilder): String = {
    val input = in.read()
    if (input != -1) {
      readRecur(in, sb.append(input.toChar))
    } else sb.toString()
  }
}

class Server(port: Int) extends Thread with InputReader {
  val socket = new ServerSocket(port)
  override def run(): Unit = {
    while (true) {
      println("Server accepting connections...")
      val connectionSocket = socket.accept()
      println(s"Server Accepted Connection: $connectionSocket")

      val in = connectionSocket.getInputStream
      val message = readRecur(in)

      println(s"Received: $message")
      val response =
        """
          |HTTP/1.1 200 OK
          |
          |
          |Yay you win
          |""".stripMargin
      connectionSocket.getOutputStream.write(response.getBytes("UTF-8"))
      connectionSocket.shutdownOutput()
    }
  }
}

class ProxyServer(address: String, port: Int, proxyPort: Int)
    extends Thread
    with InputReader {
  val proxySocket = new ServerSocket(proxyPort)

  override def run(): Unit = {
    while (true) {
      println("Proxy accepting connections...")
      val connectionSocket = proxySocket.accept()
      val connectionInputStream = connectionSocket.getInputStream
      println(s"Proxy Accepted Connection: $connectionSocket")

      val serverSocket = new Socket(address, port)
      val serverInputStream = serverSocket.getInputStream

      val message: String = readRecur(connectionInputStream)
      println(s"Proxy server received: $message")
      serverSocket.getOutputStream.write(message.getBytes("UTF-8"))
      serverSocket.shutdownOutput()

      val response = readRecur(serverInputStream)
      println(s"Proxy server received $response from server")
      connectionSocket.getOutputStream.write(response.getBytes("UTF-8"))
      connectionSocket.shutdownOutput()
    }
  }
}

object ProxyServer extends InputReader {
  def main(args: Array[String]): Unit = {
    val server = new Server(2222)
    println("starting server")
    server.start()

    val proxyServer = new ProxyServer("0.0.0.0", 2222, 3333)
    println("starting proxy server")
    proxyServer.start()

    // Begin testing
    val proxyServerSocket = new Socket("0.0.0.0", 2222)
    val message: String = "Hello!"
    println(s"Client sending message: $message")
    proxyServerSocket.getOutputStream.write(message.getBytes("UTF-8"))
    proxyServerSocket.shutdownOutput()

    val response = readRecur(proxyServerSocket.getInputStream)
    println(s"Client received: $response")

    server.stop()

  }
}

顯然問題出在讀取操作上，他們永遠不知道什么時候停止期待更多。 套接字通信是非常基本的，客戶端和服務器必須就協議（如 http 之類的）達成一致，以確保它們相互理解。

在上面的例子中，我創建了一個非常基本的閱讀器，它會一直閱讀，直到通信從另一端標記為完成。

Answer 2

在這種特殊情況下，您可以在編寫服務器響應后添加connectionSocket.close()使其工作。