Try Netty

NettyExample.scala

import io.netty.bootstrap.ServerBootstrap
import io.netty.channel.{ChannelOption, ChannelHandlerContext, ChannelInitializer, ChannelInboundHandlerAdapter}
import io.netty.channel.nio.NioEventLoopGroup
import io.netty.channel.socket.SocketChannel
import io.netty.channel.socket.nio.NioServerSocketChannel
import io.netty.channel.group.{ChannelGroup, DefaultChannelGroup}
import io.netty.handler.codec.http.{HttpObjectAggregator, HttpServerCodec}
import io.netty.handler.logging.{LogLevel, LoggingHandler}
import io.netty.channel.ChannelHandler.Sharable
import io.netty.handler.codec.http._
import io.netty.util.ReferenceCountUtil
import io.netty.buffer.Unpooled


@Sharable
class HelloServerHandler extends ChannelInboundHandlerAdapter {
  
  override def channelRead(ctx: ChannelHandlerContext, msg: Object): Unit = {
    msg match {
      case req: FullHttpRequest => 
        val response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, Unpooled.copiedBuffer("hello world".getBytes()))
        response.headers.set("Content-Type", "text/plain")
        response.headers.set("Server", "Netty/4.1")
        response.headers.set("Content-Length", "11")
        ctx.write(response)
        req.release()
      case _ => ReferenceCountUtil.release(msg)
    }
  }

  override def channelReadComplete(ctx: ChannelHandlerContext): Unit = {
    ctx.flush()
  }

  override def exceptionCaught(ctx: ChannelHandlerContext, cause: Throwable): Unit = {
    ctx.close()
  }
}

object NettyExample {
  def main(args: Array[String]): Unit = {
    
    val master, worker = new NioEventLoopGroup()

    try {
      new ServerBootstrap()
        .group(master, worker)
        .channel(classOf[NioServerSocketChannel])
        .handler(new LoggingHandler(LogLevel.INFO))
        .childHandler(new ChannelInitializer[SocketChannel] {
            override def initChannel(ch: SocketChannel): Unit = {
              ch.pipeline
                .addLast(new HttpServerCodec)
                .addLast(new HttpObjectAggregator(65536))
                .addLast(new HelloServerHandler)
            }
        })
        .bind(8080).sync()
        .channel()
        .closeFuture().sync()
    } finally {
      master.shutdownGracefully()
      worker.shutdownGracefully()
    }
  }
}