June 2018 Update

Task/Echo-server/Scala/echo-server.scala

@@ -0,0 +1,30 @@
+import java.io.PrintWriter
+import java.net.{ServerSocket, Socket}
+
+import scala.io.Source
+
+object EchoServer extends App {
+  private val serverSocket = new ServerSocket(23)
+  private var numConnections = 0
+
+  class ClientHandler(clientSocket: Socket) extends Runnable {
+    private val (connectionId, closeCmd) = ({numConnections += 1; numConnections}, ":exit")
+
+    override def run(): Unit =
+      new PrintWriter(clientSocket.getOutputStream, true) {
+        println(s"Connection opened, close with entering '$closeCmd'.")
+        Source.fromInputStream(clientSocket.getInputStream).getLines
+          .takeWhile(!_.toLowerCase.startsWith(closeCmd))
+          .foreach { line =>
+            Console.println(s"Received on #$connectionId: $line")
+            println(line)  // Echo
+          }
+        Console.println(s"Gracefully closing connection, #$connectionId")
+        clientSocket.close()
+    }
+
+    println(s"Handling connection, $connectionId")
+  }
+
+  while (true) new Thread(new ClientHandler(serverSocket.accept())).start()
+}