A minimalist wrapper for Netty in terms of scalaz-stream


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Getting Started

First, you'll need to add the RichRelevance Bintray resolver setting to your SBT file:

resolvers += "RichRelevance Bintray" at "http://dl.bintray.com/rr/releases"

If you want to be able to use snapshot releases, replace releases with snapshots. With the resolver configured, add the following dependency specification:

libraryDependencies += "org.scalaz.netty" %% "scalaz-netty" % "0.4.2"

Builds are published for Scala 2.11.8, and for 2.12.x for versions at or above 0.4.2. The latest stable release is 0.4.2.

Versions that end in 'a' in the 0.3.x series use scalaz 7.2.x, versions without use scalaz 7.1.x.

The 0.3.2 versions contain one additional feature over the 0.3, #28, which has only been tested on Linux and may not work elsewhere.

The upstream dependencies for this project include the following:

For version 0.4.1 and 0.4.2:

  • scalaz 7.2.7
  • scalaz-stream 0.8.6a
  • scodec-bits 1.1.2
  • netty 4.0.42.Final

For version 0.4:

  • scalaz 7.2.5
  • scalaz-stream 0.8.4a
  • scodec-bits 1.1.0
  • netty 4.0.40.Final

For version 0.3 and 0.3.2:

  • scalaz 7.1.7
  • scalaz-stream 0.8
  • scodec-bits 1.0.12
  • netty 4.0.36.Final

And for version 0.3a and 0.3.2a:

  • scalaz 7.2.2
  • scalaz-stream 0.8a
  • scodec-bits 1.0.12
  • netty 4.0.36.Final

Snapshot releases follow the version scheme master-<sha1>, where the "sha1" component is the Git commit that was snapshotted. Not all commits will have corresponding snapshot releases. You can browse the list of snapshot releases on bintray.


import scalaz.netty._
import scalaz.stream._
import scalaz.concurrent._
import java.net.InetSocketAddress
import scodec.bits.ByteVector

 * A simple server which accepts a connection, echos the incoming
 * data back to the sender, waiting for the client to close the connection.

def log(msg: String): Task[Unit] = Task.delay(println(s"$msg"))

val address = new InetSocketAddress("localhost", 9090)

val EchoServer = merge.mergeN(Netty server address map { incoming =>
  for {
    exchange <- incoming
    _ <- Process.eval(log("accepted connection"))
    _ <- exchange.read to exchange.write
  } yield ()

 * A simple client which sends ByteVector(1, 2, 3) to the server,
 * prints its response and then shuts down.

val BasicClient = Netty connect address flatMap { exchange =>
  for {
    _ <- Process(ByteVector(1, 2, 3)) to exchange.write
    data <- exchange.read take 1
    _ <- Process.eval(log(s"received data = $data"))
  } yield ()

// Usage:
// scala> EchoServer.run.runAsync(_ => ())  // press Enter when this completes to acquire new prompt
// scala> BasicClient.run.run

Future Work

  • Byte buffers are copied upon receipt. The only way to safely address this problem will be to integrate with Scodec and decode against the directly allocated byte buffers. Not hard to do, really...
  • Exceptions probably don't propagate properly under all circumstances.


Licensed under the Apache License 2.0. For more information, please see LICENSE.txt. Opening a pull request signifies your consent to license your contributions under the Apache License 2.0. Don't open a pull request if you don't know what this means.