From b550a83e80dcb2eeb081c8dc59fef322f5135446 Mon Sep 17 00:00:00 2001
From: Lachlan O'Dea <lodea@mac.com>
Date: Tue, 29 Sep 2020 11:13:06 +1000
Subject: [PATCH 1/7] Improve InetSocketAddress and socket binding APIs.

Use meaningful names for the InetSocketAddress
constructors.

Make binding to an automatically assigned socket
address explicit.
---
 .../src/main/scala/StreamsBasedServer.scala   |  4 +-
 .../zio/nio/core/InetSocketAddress.scala      | 54 ++++++-------
 .../core/channels/AsynchronousChannel.scala   | 25 +++---
 .../nio/core/channels/DatagramChannel.scala   |  4 +
 .../nio/core/channels/SelectableChannel.scala | 16 ++--
 .../zio/nio/core/channels/ChannelSpec.scala   | 80 +++++++++----------
 .../core/channels/DatagramChannelSpec.scala   | 42 +++++-----
 .../zio/nio/core/channels/SelectorSpec.scala  |  3 +-
 .../nio/channels/AsynchronousChannel.scala    | 15 ++--
 .../zio/nio/channels/DatagramChannel.scala    | 15 ++++
 .../zio/nio/channels/SelectableChannel.scala  | 30 +++----
 .../scala/zio/nio/channels/ChannelSpec.scala  | 22 ++---
 .../nio/channels/DatagramChannelSpec.scala    |  6 +-
 .../scala/zio/nio/channels/SelectorSpec.scala |  7 +-
 14 files changed, 173 insertions(+), 150 deletions(-)

diff --git a/examples/src/main/scala/StreamsBasedServer.scala b/examples/src/main/scala/StreamsBasedServer.scala
index fae9b9ab..a9282048 100644
--- a/examples/src/main/scala/StreamsBasedServer.scala
+++ b/examples/src/main/scala/StreamsBasedServer.scala
@@ -3,7 +3,7 @@ import zio.clock.Clock
 import zio.console.Console
 import zio.duration._
 import zio.nio.channels._
-import zio.nio.core.SocketAddress
+import zio.nio.core.InetSocketAddress
 import zio.stream._
 
 object StreamsBasedServer extends App {
@@ -16,7 +16,7 @@ object StreamsBasedServer extends App {
     AsynchronousServerSocketChannel()
       .use(socket =>
         for {
-          _ <- SocketAddress.inetSocketAddress("localhost", port) >>= socket.bind
+          _ <- InetSocketAddress.hostname("localhost", port).flatMap(socket.bindTo(_))
           _ <- ZStream
                  .repeatEffect(socket.accept.preallocate)
                  .map(_.withEarlyRelease)
diff --git a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
index 7fd6ab26..5fc585de 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
@@ -22,6 +22,18 @@ sealed class SocketAddress private[nio] (private[nio] val jSocketAddress: JSocke
   final override def toString: String = jSocketAddress.toString
 }
 
+object SocketAddress {
+
+  def fromJava(jSocketAddress: JSocketAddress): SocketAddress =
+    jSocketAddress match {
+      case inet: JInetSocketAddress =>
+        new InetSocketAddress(inet)
+      case other                    =>
+        new SocketAddress(other)
+    }
+
+}
+
 /**
  * Representation of an IP Socket Address (IP address + port number).
  *
@@ -75,29 +87,26 @@ final class InetSocketAddress private[nio] (private val jInetSocketAddress: JIne
 
 }
 
-object SocketAddress {
-
-  private[nio] def fromJava(jSocketAddress: JSocketAddress) =
-    jSocketAddress match {
-      case inet: JInetSocketAddress =>
-        new InetSocketAddress(inet)
-      case other                    =>
-        new SocketAddress(other)
-    }
+object InetSocketAddress {
 
   /**
    * Creates a socket address where the IP address is the wildcard address and the port number a specified value.
    *
    * The socket address will be ''resolved''.
    */
-  def inetSocketAddress(port: Int): UIO[InetSocketAddress] = InetSocketAddress(port)
+  def wildCard(port: Int): UIO[InetSocketAddress] = UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(port)))
+
+  def wildCardEphemeral: UIO[InetSocketAddress] = wildCard(0)
 
   /**
    * Creates a socket address from an IP address and a port number.
    *
    * The socket address will be ''resolved''.
    */
-  def inetSocketAddress(hostname: String, port: Int): UIO[InetSocketAddress] = InetSocketAddress(hostname, port)
+  def hostname(hostname: String, port: Int): UIO[InetSocketAddress] =
+    UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(hostname, port)))
+
+  def hostnameEphemeral(hostname: String): UIO[InetSocketAddress] = this.hostname(hostname, 0)
 
   /**
    * Creates a socket address from a hostname and a port number.
@@ -105,7 +114,10 @@ object SocketAddress {
    * An attempt will be made to resolve the hostname into an `InetAddress`.
    * If that attempt fails, the socket address will be flagged as ''unresolved''.
    */
-  def inetSocketAddress(address: InetAddress, port: Int): UIO[InetSocketAddress] = InetSocketAddress(address, port)
+  def inetAddress(address: InetAddress, port: Int): UIO[InetSocketAddress] =
+    UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(address.jInetAddress, port)))
+
+  def inetAddressEphemeral(address: InetAddress): UIO[InetSocketAddress] = inetAddress(address, 0)
 
   /**
    * Creates an unresolved socket address from a hostname and a port number.
@@ -113,21 +125,9 @@ object SocketAddress {
    * No attempt will be made to resolve the hostname into an `InetAddress`.
    * The socket address will be flagged as ''unresolved''.
    */
-  def unresolvedInetSocketAddress(hostname: String, port: Int): UIO[InetSocketAddress] =
-    InetSocketAddress.createUnresolved(hostname, port)
-
-  private object InetSocketAddress {
-
-    def apply(port: Int): UIO[InetSocketAddress] = UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(port)))
-
-    def apply(host: String, port: Int): UIO[InetSocketAddress] =
-      UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(host, port)))
-
-    def apply(addr: InetAddress, port: Int): UIO[InetSocketAddress] =
-      UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(addr.jInetAddress, port)))
+  def unresolvedHostname(hostname: String, port: Int): UIO[InetSocketAddress] =
+    UIO.effectTotal(new InetSocketAddress(JInetSocketAddress.createUnresolved(hostname, port)))
 
-    def createUnresolved(host: String, port: Int): UIO[InetSocketAddress] =
-      UIO.effectTotal(new InetSocketAddress(JInetSocketAddress.createUnresolved(host, port)))
+  def unresolvedHostnameEphemeral(hostname: String): UIO[InetSocketAddress] = unresolvedHostname(hostname, 0)
 
-  }
 }
diff --git a/nio-core/src/main/scala/zio/nio/core/channels/AsynchronousChannel.scala b/nio-core/src/main/scala/zio/nio/core/channels/AsynchronousChannel.scala
index bc605ec3..53ba58b7 100644
--- a/nio-core/src/main/scala/zio/nio/core/channels/AsynchronousChannel.scala
+++ b/nio-core/src/main/scala/zio/nio/core/channels/AsynchronousChannel.scala
@@ -65,19 +65,16 @@ abstract class AsynchronousByteChannel private[channels] (protected val channel:
 
 final class AsynchronousServerSocketChannel(protected val channel: JAsynchronousServerSocketChannel) extends Channel {
 
-  /**
-   * Binds the channel's socket to a local address and configures the socket
-   * to listen for connections.
-   */
-  def bind(address: SocketAddress): IO[IOException, Unit] =
-    IO.effect(channel.bind(address.jSocketAddress)).refineToOrDie[IOException].unit
+  def bindTo(local: SocketAddress, backlog: Int = 0): IO[IOException, Unit] = bind(Some(local), backlog)
+
+  def bindAuto(backlog: Int = 0): IO[IOException, Unit] = bind(None, backlog)
 
   /**
    * Binds the channel's socket to a local address and configures the socket
    * to listen for connections, up to backlog pending connection.
    */
-  def bind(address: SocketAddress, backlog: Int): IO[IOException, Unit] =
-    IO.effect(channel.bind(address.jSocketAddress, backlog)).refineToOrDie[IOException].unit
+  def bind(address: Option[SocketAddress], backlog: Int = 0): IO[IOException, Unit] =
+    IO.effect(channel.bind(address.map(_.jSocketAddress).orNull, backlog)).refineToOrDie[IOException].unit
 
   def setOption[T](name: SocketOption[T], value: T): IO[IOException, Unit] =
     IO.effect(channel.setOption(name, value)).refineToOrDie[IOException].unit
@@ -119,13 +116,17 @@ object AsynchronousServerSocketChannel {
       .toNioManaged
 }
 
-class AsynchronousSocketChannel(override protected val channel: JAsynchronousSocketChannel)
+final class AsynchronousSocketChannel(override protected val channel: JAsynchronousSocketChannel)
     extends AsynchronousByteChannel(channel) {
 
-  final def bind(address: SocketAddress): IO[IOException, Unit] =
-    IO.effect(channel.bind(address.jSocketAddress)).refineToOrDie[IOException].unit
+  def bindTo(address: SocketAddress): IO[IOException, Unit] = bind(Some(address))
 
-  final def setOption[T](name: SocketOption[T], value: T): IO[IOException, Unit] =
+  def bindAuto: IO[IOException, Unit] = bind(None)
+
+  def bind(address: Option[SocketAddress]): IO[IOException, Unit] =
+    IO.effect(channel.bind(address.map(_.jSocketAddress).orNull)).refineToOrDie[IOException].unit
+
+  def setOption[T](name: SocketOption[T], value: T): IO[IOException, Unit] =
     IO.effect(channel.setOption(name, value)).refineToOrDie[IOException].unit
 
   final def shutdownInput: IO[IOException, Unit] = IO.effect(channel.shutdownInput()).refineToOrDie[IOException].unit
diff --git a/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala b/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala
index f8599ee0..5a516699 100644
--- a/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala
+++ b/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala
@@ -15,6 +15,10 @@ final class DatagramChannel private[channels] (override protected[channels] val
     with SelectableChannel
     with ScatteringByteChannel {
 
+  def bindTo(local: SocketAddress): IO[IOException, Unit] = bind(Some(local))
+
+  def bindAuto: IO[IOException, Unit] = bind(None)
+
   /**
    * Binds this channel's underlying socket to the given local address. Passing `None` binds to an
    * automatically assigned local address.
diff --git a/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala b/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala
index 9cc8b9b9..c694f168 100644
--- a/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala
+++ b/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala
@@ -63,8 +63,12 @@ final class SocketChannel(override protected[channels] val channel: JSocketChann
     with GatheringByteChannel
     with ScatteringByteChannel {
 
-  def bind(local: SocketAddress): IO[IOException, Unit] =
-    IO.effect(channel.bind(local.jSocketAddress)).refineToOrDie[IOException].unit
+  def bindTo(address: SocketAddress): IO[IOException, Unit] = bind(Some(address))
+
+  def bindAuto: IO[IOException, Unit] = bind(None)
+
+  def bind(local: Option[SocketAddress]): IO[IOException, Unit] =
+    IO.effect(channel.bind(local.map(_.jSocketAddress).orNull)).refineToOrDie[IOException].unit
 
   def setOption[T](name: SocketOption[T], value: T): IO[IOException, Unit] =
     IO.effect(channel.setOption(name, value)).refineToOrDie[IOException].unit
@@ -110,12 +114,12 @@ object SocketChannel {
 }
 
 final class ServerSocketChannel(override protected val channel: JServerSocketChannel) extends SelectableChannel {
+  def bindTo(local: SocketAddress, backlog: Int = 0): IO[IOException, Unit] = bind(Some(local), backlog)
 
-  def bind(local: SocketAddress): IO[IOException, Unit] =
-    IO.effect(channel.bind(local.jSocketAddress)).refineToOrDie[IOException].unit
+  def bindAuto(backlog: Int = 0): IO[IOException, Unit] = bind(None, backlog)
 
-  def bind(local: SocketAddress, backlog: Int): IO[IOException, Unit] =
-    IO.effect(channel.bind(local.jSocketAddress, backlog)).refineToOrDie[IOException].unit
+  def bind(local: Option[SocketAddress], backlog: Int = 0): IO[IOException, Unit] =
+    IO.effect(channel.bind(local.map(_.jSocketAddress).orNull, backlog)).refineToOrDie[IOException].unit
 
   def setOption[T](name: SocketOption[T], value: T): IO[IOException, Unit] =
     IO.effect(channel.setOption(name, value)).refineToOrDie[IOException].unit
diff --git a/nio-core/src/test/scala/zio/nio/core/channels/ChannelSpec.scala b/nio-core/src/test/scala/zio/nio/core/channels/ChannelSpec.scala
index 2f37951a..6ae0c962 100644
--- a/nio-core/src/test/scala/zio/nio/core/channels/ChannelSpec.scala
+++ b/nio-core/src/test/scala/zio/nio/core/channels/ChannelSpec.scala
@@ -1,11 +1,11 @@
 package zio.nio.core.channels
 
-import java.io.{ EOFException, FileNotFoundException, IOException }
-
 import zio.nio.core.{ BaseSpec, Buffer, EffectOps, SocketAddress }
-import zio.{ IO, _ }
-import zio.test._
 import zio.test.Assertion._
+import zio.test._
+import zio.{ IO, _ }
+
+import java.io.{ EOFException, FileNotFoundException, IOException }
 
 object ChannelSpec extends BaseSpec {
 
@@ -14,23 +14,22 @@ object ChannelSpec extends BaseSpec {
       testM("read/write") {
         def echoServer(started: Promise[Nothing, SocketAddress]): IO[Exception, Unit] =
           for {
-            address <- SocketAddress.inetSocketAddress(0)
-            sink    <- Buffer.byte(3)
-            _       <- AsynchronousServerSocketChannel
-                         .open()
-                         .use { server =>
-                           for {
-                             _    <- server.bind(address)
-                             addr <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
-                             _    <- started.succeed(addr)
-                             _    <- server.accept.use { worker =>
-                                       worker.read(sink) *>
-                                         sink.flip *>
-                                         worker.write(sink)
-                                     }
-                           } yield ()
-                         }
-                         .fork
+            sink <- Buffer.byte(3)
+            _    <- AsynchronousServerSocketChannel
+                      .open()
+                      .use { server =>
+                        for {
+                          _    <- server.bindAuto()
+                          addr <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
+                          _    <- started.succeed(addr)
+                          _    <- server.accept.use { worker =>
+                                    worker.read(sink) *>
+                                      sink.flip *>
+                                      worker.write(sink)
+                                  }
+                        } yield ()
+                      }
+                      .fork
           } yield ()
 
         def echoClient(address: SocketAddress): IO[Exception, Boolean] =
@@ -59,22 +58,21 @@ object ChannelSpec extends BaseSpec {
       testM("read should fail when connection close") {
         def server(started: Promise[Nothing, SocketAddress]): IO[Exception, Fiber[Exception, Boolean]] =
           for {
-            address <- SocketAddress.inetSocketAddress(0)
-            result  <- AsynchronousServerSocketChannel
-                         .open()
-                         .use { server =>
-                           for {
-                             _      <- server.bind(address)
-                             addr   <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
-                             _      <- started.succeed(addr)
-                             result <- server.accept
-                                         .use(worker => worker.readChunk(3) *> worker.readChunk(3) *> ZIO.succeed(false))
-                                         .catchSome { case _: java.io.EOFException =>
-                                           ZIO.succeed(true)
-                                         }
-                           } yield result
-                         }
-                         .fork
+            result <- AsynchronousServerSocketChannel
+                        .open()
+                        .use { server =>
+                          for {
+                            _      <- server.bindAuto()
+                            addr   <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
+                            _      <- started.succeed(addr)
+                            result <- server.accept
+                                        .use(worker => worker.readChunk(3) *> worker.readChunk(3) *> ZIO.succeed(false))
+                                        .catchSome { case _: java.io.EOFException =>
+                                          ZIO.succeed(true)
+                                        }
+                          } yield result
+                        }
+                        .fork
           } yield result
 
         def client(address: SocketAddress): IO[Exception, Unit] =
@@ -102,25 +100,23 @@ object ChannelSpec extends BaseSpec {
           }
 
         def server(
-          address: SocketAddress,
           started: Promise[Nothing, SocketAddress]
         ): Managed[IOException, Fiber[Exception, Unit]] =
           for {
             server <- AsynchronousServerSocketChannel.open()
-            _      <- server.bind(address).toManaged_
+            _      <- server.bindAuto().toManaged_
             addr   <- server.localAddress.someOrElseM(IO.die(new NoSuchElementException)).toManaged_
             _      <- started.succeed(addr).toManaged_
             worker <- server.accept.unit.fork
           } yield worker
 
         for {
-          address        <- SocketAddress.inetSocketAddress(0)
           serverStarted1 <- Promise.make[Nothing, SocketAddress]
-          _              <- server(address, serverStarted1).use { s1 =>
+          _              <- server(serverStarted1).use { s1 =>
                               serverStarted1.await.flatMap(client).zipRight(s1.join)
                             }
           serverStarted2 <- Promise.make[Nothing, SocketAddress]
-          _              <- server(address, serverStarted2).use { s2 =>
+          _              <- server(serverStarted2).use { s2 =>
                               serverStarted2.await.flatMap(client).zipRight(s2.join)
                             }
         } yield assertCompletes
diff --git a/nio-core/src/test/scala/zio/nio/core/channels/DatagramChannelSpec.scala b/nio-core/src/test/scala/zio/nio/core/channels/DatagramChannelSpec.scala
index 973742c3..df39257f 100644
--- a/nio-core/src/test/scala/zio/nio/core/channels/DatagramChannelSpec.scala
+++ b/nio-core/src/test/scala/zio/nio/core/channels/DatagramChannelSpec.scala
@@ -1,11 +1,11 @@
 package zio.nio.core.channels
 
-import java.io.IOException
-
+import zio.{ IO, _ }
 import zio.nio.core._
 import zio.test.Assertion._
 import zio.test._
-import zio.{ IO, _ }
+
+import java.io.IOException
 
 object DatagramChannelSpec extends BaseSpec {
 
@@ -14,19 +14,18 @@ object DatagramChannelSpec extends BaseSpec {
       testM("read/write") {
         def echoServer(started: Promise[Nothing, SocketAddress]): IO[IOException, Unit] =
           for {
-            address <- SocketAddress.inetSocketAddress(0)
-            sink    <- Buffer.byte(3)
-            _       <- DatagramChannel.open.use { server =>
-                         for {
-                           _          <- server.bind(Some(address))
-                           addr       <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
-                           _          <- started.succeed(addr)
-                           retAddress <- server.receive(sink)
-                           addr       <- IO.fromOption(retAddress)
-                           _          <- sink.flip
-                           _          <- server.send(sink, addr)
-                         } yield ()
-                       }.fork
+            sink <- Buffer.byte(3)
+            _    <- DatagramChannel.open.use { server =>
+                      for {
+                        _          <- server.bindAuto
+                        addr       <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
+                        _          <- started.succeed(addr)
+                        retAddress <- server.receive(sink)
+                        addr       <- IO.fromOption(retAddress)
+                        _          <- sink.flip
+                        _          <- server.send(sink, addr)
+                      } yield ()
+                    }.fork
           } yield ()
 
         def echoClient(address: SocketAddress): IO[IOException, Boolean] =
@@ -56,28 +55,27 @@ object DatagramChannelSpec extends BaseSpec {
         def client(address: SocketAddress): IO[IOException, Unit] = DatagramChannel.open.use(_.connect(address).unit)
 
         def server(
-          address: SocketAddress,
+          address: Option[SocketAddress],
           started: Promise[Nothing, SocketAddress]
         ): IO[Nothing, Fiber[IOException, Unit]] =
           for {
             worker <- DatagramChannel.open.use { server =>
                         for {
-                          _    <- server.bind(Some(address))
-                          addr <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
+                          _    <- server.bind(address)
+                          addr <- server.localAddress.someOrElseM(ZIO.dieMessage("Local address must be bound"))
                           _    <- started.succeed(addr)
                         } yield ()
                       }.fork
           } yield worker
 
         for {
-          address        <- SocketAddress.inetSocketAddress(0)
           serverStarted  <- Promise.make[Nothing, SocketAddress]
-          s1             <- server(address, serverStarted)
+          s1             <- server(None, serverStarted)
           addr           <- serverStarted.await
           _              <- client(addr)
           _              <- s1.join
           serverStarted2 <- Promise.make[Nothing, SocketAddress]
-          s2             <- server(addr, serverStarted2)
+          s2             <- server(Some(addr), serverStarted2)
           _              <- serverStarted2.await
           _              <- client(addr)
           _              <- s2.join
diff --git a/nio-core/src/test/scala/zio/nio/core/channels/SelectorSpec.scala b/nio-core/src/test/scala/zio/nio/core/channels/SelectorSpec.scala
index d25a28d3..249eb9b0 100644
--- a/nio-core/src/test/scala/zio/nio/core/channels/SelectorSpec.scala
+++ b/nio-core/src/test/scala/zio/nio/core/channels/SelectorSpec.scala
@@ -65,13 +65,12 @@ object SelectorSpec extends BaseSpec {
       } yield ()
 
     for {
-      address  <- SocketAddress.inetSocketAddress(0).toManaged_
       scope    <- Managed.scope
       selector <- Selector.open
       channel  <- ServerSocketChannel.open
       _        <- Managed.fromEffect {
                     for {
-                      _      <- channel.bind(address)
+                      _      <- channel.bindAuto()
                       _      <- channel.configureBlocking(false)
                       _      <- channel.register(selector, Operation.Accept)
                       buffer <- Buffer.byte(256)
diff --git a/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala b/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala
index e8abbcf1..8fa283fa 100644
--- a/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala
+++ b/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala
@@ -67,17 +67,22 @@ class AsynchronousServerSocketChannel(private val channel: JAsynchronousServerSo
 
   /**
    * Binds the channel's socket to a local address and configures the socket
-   * to listen for connections.
+   * to listen for connections, up to backlog pending connection.
    */
-  final def bind(address: SocketAddress): IO[IOException, Unit] =
-    IO.effect(channel.bind(address.jSocketAddress)).refineToOrDie[IOException].unit
+  final def bindTo(local: SocketAddress, backlog: Int = 0): IO[IOException, Unit] = bind(Some(local), backlog)
+
+  /**
+   * Binds the channel's socket to an automatically assigned local address and configures the socket
+   * to listen for connections, up to backlog pending connection.
+   */
+  final def bindAuto(backlog: Int = 0): IO[IOException, Unit] = bind(None, backlog)
 
   /**
    * Binds the channel's socket to a local address and configures the socket
    * to listen for connections, up to backlog pending connection.
    */
-  final def bind(address: SocketAddress, backlog: Int): IO[IOException, Unit] =
-    IO.effect(channel.bind(address.jSocketAddress, backlog)).refineToOrDie[IOException].unit
+  final def bind(address: Option[SocketAddress], backlog: Int = 0): IO[IOException, Unit] =
+    IO.effect(channel.bind(address.map(_.jSocketAddress).orNull, backlog)).refineToOrDie[IOException].unit
 
   final def setOption[T](name: SocketOption[T], value: T): IO[IOException, Unit] =
     IO.effect(channel.setOption(name, value)).refineToOrDie[IOException].unit
diff --git a/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala b/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala
index cb06c3ba..2fc56851 100644
--- a/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala
+++ b/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala
@@ -109,6 +109,21 @@ object DatagramChannel {
    */
   def bind(local: Option[SocketAddress]): Managed[IOException, DatagramChannel] = open.flatMap(_.bind(local).toManaged_)
 
+  /**
+   * Opens a datagram channel bound to the given local address as a managed resource.
+   *
+   * @param local the local address
+   * @return a datagram channel bound to the local address
+   */
+  def bindTo(local: SocketAddress): Managed[IOException, DatagramChannel] = open.flatMap(_.bind(Some(local)).toManaged_)
+
+  /**
+   * Opens a datagram channel bound to an automatically assigned local address as a managed resource.
+   *
+   * @return a datagram channel bound to the local address
+   */
+  def bindAuto: Managed[IOException, DatagramChannel] = open.flatMap(_.bind(None).toManaged_)
+
   /**
    * Opens a datagram channel connected to the given remote address as a managed resource.
    *
diff --git a/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala b/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala
index 612c7952..1cb81935 100644
--- a/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala
+++ b/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala
@@ -1,5 +1,11 @@
 package zio.nio.channels
 
+import zio.nio.channels.spi.SelectorProvider
+import zio.nio.core.SocketAddress
+import zio.nio.core.channels.SelectionKey
+import zio.nio.core.channels.SelectionKey.Operation
+import zio.{ IO, Managed, UIO }
+
 import java.io.IOException
 import java.net.{ SocketOption, ServerSocket => JServerSocket, Socket => JSocket }
 import java.nio.channels.{
@@ -8,12 +14,6 @@ import java.nio.channels.{
   SocketChannel => JSocketChannel
 }
 
-import zio.{ IO, Managed, UIO }
-import zio.nio.channels.spi.SelectorProvider
-import zio.nio.core.{ SocketAddress }
-import zio.nio.core.channels.SelectionKey
-import zio.nio.core.channels.SelectionKey.Operation
-
 trait SelectableChannel extends Channel {
   protected val channel: JSelectableChannel
 
@@ -61,8 +61,12 @@ final class SocketChannel private[channels] (override protected[channels] val ch
     with GatheringByteChannel
     with ScatteringByteChannel {
 
-  final def bind(local: SocketAddress): IO[IOException, Unit] =
-    IO.effect(channel.bind(local.jSocketAddress)).refineToOrDie[IOException].unit
+  final def bindTo(address: SocketAddress): IO[IOException, Unit] = bind(Some(address))
+
+  final def bindAuto: IO[IOException, Unit] = bind(None)
+
+  final def bind(local: Option[SocketAddress]): IO[IOException, Unit] =
+    IO.effect(channel.bind(local.map(_.jSocketAddress).orNull)).refineToOrDie[IOException].unit
 
   final def setOption[T](name: SocketOption[T], value: T): IO[IOException, Unit] =
     IO.effect(channel.setOption(name, value)).refineToOrDie[IOException].unit
@@ -122,14 +126,12 @@ object SocketChannel {
 final class ServerSocketChannel private (override protected val channel: JServerSocketChannel)
     extends SelectableChannel {
 
-  final def bind(local: SocketAddress): IO[IOException, Unit] =
-    IO.effect(channel.bind(local.jSocketAddress)).refineToOrDie[IOException].unit
+  final def bindTo(local: SocketAddress, backlog: Int = 0): IO[IOException, Unit] = bind(Some(local), backlog)
 
-  final def bind(local: SocketAddress, backlog: Int): IO[IOException, Unit] =
-    IO.effect(channel.bind(local.jSocketAddress, backlog)).refineToOrDie[IOException].unit
+  final def bindAuto(backlog: Int = 0): IO[IOException, Unit] = bind(None, backlog)
 
-  final def setOption[T](name: SocketOption[T], value: T): IO[Exception, Unit] =
-    IO.effect(channel.setOption(name, value)).refineToOrDie[Exception].unit
+  final def bind(local: Option[SocketAddress], backlog: Int = 0): IO[IOException, Unit] =
+    IO.effect(channel.bind(local.map(_.jSocketAddress).orNull, backlog)).refineToOrDie[IOException].unit
 
   final val socket: UIO[JServerSocket] =
     IO.effectTotal(channel.socket())
diff --git a/nio/src/test/scala/zio/nio/channels/ChannelSpec.scala b/nio/src/test/scala/zio/nio/channels/ChannelSpec.scala
index 0653b543..8ff8d7e1 100644
--- a/nio/src/test/scala/zio/nio/channels/ChannelSpec.scala
+++ b/nio/src/test/scala/zio/nio/channels/ChannelSpec.scala
@@ -1,7 +1,7 @@
 package zio.nio.channels
 
 import zio.nio.BaseSpec
-import zio.nio.core.{ Buffer, SocketAddress }
+import zio.nio.core.{ Buffer, InetSocketAddress, SocketAddress }
 import zio.{ IO, _ }
 import zio.test._
 import zio.test.Assertion._
@@ -14,11 +14,11 @@ object ChannelSpec extends BaseSpec {
       testM("read/write") {
         def echoServer(started: Promise[Nothing, SocketAddress]): IO[Exception, Unit] =
           for {
-            address <- SocketAddress.inetSocketAddress(0)
+            address <- InetSocketAddress.wildCard(0)
             sink    <- Buffer.byte(3)
             _       <- AsynchronousServerSocketChannel().use { server =>
                          for {
-                           _    <- server.bind(address)
+                           _    <- server.bindTo(address)
                            addr <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
                            _    <- started.succeed(addr)
                            _    <- server.accept.use { worker =>
@@ -56,10 +56,10 @@ object ChannelSpec extends BaseSpec {
       testM("read should fail when connection close") {
         def server(started: Promise[Nothing, SocketAddress]): IO[Exception, Fiber[Exception, Boolean]] =
           for {
-            address <- SocketAddress.inetSocketAddress(0)
+            address <- InetSocketAddress.wildCard(0)
             result  <- AsynchronousServerSocketChannel().use { server =>
                          for {
-                           _      <- server.bind(address)
+                           _      <- server.bindTo(address)
                            addr   <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
                            _      <- started.succeed(addr)
                            result <- server.accept
@@ -100,7 +100,7 @@ object ChannelSpec extends BaseSpec {
           for {
             worker <- AsynchronousServerSocketChannel().use { server =>
                         for {
-                          _      <- server.bind(address)
+                          _      <- server.bindTo(address)
                           addr   <- server.localAddress.flatMap(opt => IO.effect(opt.get).orDie)
                           _      <- started.succeed(addr)
                           worker <- server.accept.use(_ => ZIO.unit)
@@ -109,7 +109,7 @@ object ChannelSpec extends BaseSpec {
           } yield worker
 
         for {
-          address       <- SocketAddress.inetSocketAddress(0)
+          address       <- InetSocketAddress.wildCard(0)
           serverStarted <- Promise.make[Nothing, SocketAddress]
           s1            <- server(address, serverStarted)
           addr          <- serverStarted.await
@@ -125,8 +125,8 @@ object ChannelSpec extends BaseSpec {
       testM("accept should be interruptible") {
         AsynchronousServerSocketChannel().use { server =>
           for {
-            addr   <- SocketAddress.inetSocketAddress(0)
-            _      <- server.bind(addr)
+            addr   <- InetSocketAddress.wildCard(0)
+            _      <- server.bindTo(addr)
             fiber  <- server.accept.useNow.fork
             _      <- fiber.interrupt
             result <- fiber.await
@@ -136,9 +136,9 @@ object ChannelSpec extends BaseSpec {
       // this would best be tagged as an regression test. for now just run manually when suspicious.
       testM("accept should not leak resources") {
         val server          = for {
-          addr    <- SocketAddress.inetSocketAddress(8081).toManaged_
+          addr    <- InetSocketAddress.wildCard(8081).toManaged_
           channel <- AsynchronousServerSocketChannel()
-          _       <- channel.bind(addr).toManaged_
+          _       <- channel.bindTo(addr).toManaged_
           _       <- AsynchronousSocketChannel().use(channel => channel.connect(addr)).forever.toManaged_.fork
         } yield channel
         val interruptAccept = server.use(
diff --git a/nio/src/test/scala/zio/nio/channels/DatagramChannelSpec.scala b/nio/src/test/scala/zio/nio/channels/DatagramChannelSpec.scala
index cfab45b9..1baadd97 100644
--- a/nio/src/test/scala/zio/nio/channels/DatagramChannelSpec.scala
+++ b/nio/src/test/scala/zio/nio/channels/DatagramChannelSpec.scala
@@ -1,7 +1,7 @@
 package zio.nio.channels
 
 import zio.nio._
-import zio.nio.core.{ Buffer, SocketAddress }
+import zio.nio.core.{ Buffer, InetSocketAddress, SocketAddress }
 import zio.test.Assertion._
 import zio.test._
 import zio._
@@ -13,7 +13,7 @@ object DatagramChannelSpec extends BaseSpec {
       testM("read/write") {
         def echoServer(started: Promise[Nothing, SocketAddress]): IO[Exception, Unit] =
           for {
-            address <- SocketAddress.inetSocketAddress(0)
+            address <- InetSocketAddress.wildCard(0)
             sink    <- Buffer.byte(3)
             _       <- DatagramChannel
                          .bind(Some(address))
@@ -72,7 +72,7 @@ object DatagramChannelSpec extends BaseSpec {
           } yield worker
 
         for {
-          address       <- SocketAddress.inetSocketAddress(0)
+          address       <- InetSocketAddress.wildCard(0)
           serverStarted <- Promise.make[Nothing, SocketAddress]
           s1            <- server(address, serverStarted)
           addr          <- serverStarted.await
diff --git a/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala b/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala
index c2dec9fa..f04f9fe5 100644
--- a/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala
+++ b/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala
@@ -1,11 +1,10 @@
 package zio.nio.channels
 
 import java.nio.channels.CancelledKeyException
-
 import zio._
 import zio.blocking.Blocking
 import zio.clock.Clock
-import zio.nio.core.{ Buffer, ByteBuffer, SocketAddress }
+import zio.nio.core.{ Buffer, ByteBuffer, InetSocketAddress, SocketAddress }
 import zio.nio.core.channels.SelectionKey.Operation
 import zio.nio.BaseSpec
 import zio.test._
@@ -68,11 +67,11 @@ object SelectorSpec extends BaseSpec {
       } yield ()
 
     for {
-      address <- SocketAddress.inetSocketAddress(0)
+      address <- InetSocketAddress.wildCard(0)
       _       <- Selector.make.use { selector =>
                    ServerSocketChannel.open.use { channel =>
                      for {
-                       _      <- channel.bind(address)
+                       _      <- channel.bindTo(address)
                        _      <- channel.configureBlocking(false)
                        _      <- channel.register(selector, Operation.Accept)
                        buffer <- Buffer.byte(256)

From 9b2b7014f5b7a6e944097c5ad8ac750753f82b66 Mon Sep 17 00:00:00 2001
From: Lachlan O'Dea <lodea@mac.com>
Date: Fri, 9 Oct 2020 20:43:29 +1100
Subject: [PATCH 2/7] Improve InetSocketAddress API.

---
 .../zio/nio/core/InetSocketAddress.scala      | 54 ++++++++++++++++---
 1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
index 5fc585de..095af550 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
@@ -1,8 +1,8 @@
 package zio.nio.core
 
-import java.net.{ InetSocketAddress => JInetSocketAddress, SocketAddress => JSocketAddress }
+import java.net.{ UnknownHostException, InetSocketAddress => JInetSocketAddress, SocketAddress => JSocketAddress }
 
-import zio.UIO
+import zio.{ IO, UIO }
 
 /**
  * Representation of a socket address without a specific protocol.
@@ -41,7 +41,10 @@ object SocketAddress {
  * will be made to resolve the hostname.
  * If resolution fails then the address is said to be unresolved but can still
  * be used on some circumstances like connecting through a proxy.
- * It provides an immutable object used by sockets for binding, connecting,
+ * However, note that network channels generally do ''not'' accept unresolved
+ * socket addresses.
+ *
+ * This class provides an immutable object used by sockets for binding, connecting,
  * or as returned values.
  *
  * The wildcard is a special local IP address. It usually means "any" and can
@@ -96,27 +99,56 @@ object InetSocketAddress {
    */
   def wildCard(port: Int): UIO[InetSocketAddress] = UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(port)))
 
+  /**
+   * Creates a socket address where the IP address is the wildcard address and
+   * the port is ephemeral.
+   *
+   * The socket address wll be ''resolved''.
+   */
   def wildCardEphemeral: UIO[InetSocketAddress] = wildCard(0)
 
   /**
-   * Creates a socket address from an IP address and a port number.
+   * Creates a socket address from a hostname and a port number.
    *
-   * The socket address will be ''resolved''.
+   * This method will attempt to resolve the hostname; if this fails, the returned
+   * socket address will be ''unresolved''.
    */
   def hostname(hostname: String, port: Int): UIO[InetSocketAddress] =
     UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(hostname, port)))
 
+  /**
+   * Creates a resolved socket address from a hostname and port number.
+   *
+   * If the hostname cannot be resolved, fails with `UnknownHostException`.
+   */
+  def hostnameResolved(hostname: String, port: Int): IO[UnknownHostException, InetSocketAddress] =
+    InetAddress.byName(hostname).flatMap(inetAddress(_, port))
+
+  /**
+   * Creates a socket address from a hostname, with an ephemeral port.
+   *
+   * This method will attempt to resolve the hostname; if this fails, the returned
+   * socket address will be ''unresolved''.
+   */
   def hostnameEphemeral(hostname: String): UIO[InetSocketAddress] = this.hostname(hostname, 0)
 
   /**
-   * Creates a socket address from a hostname and a port number.
+   * Creates a resolved socket address from a hostname, with an ephemeral port.
    *
-   * An attempt will be made to resolve the hostname into an `InetAddress`.
-   * If that attempt fails, the socket address will be flagged as ''unresolved''.
+   * If the hostname cannot be resolved, fails with `UnknownHostException`.
+   */
+  def hostnameEphemeralResolved(hostname: String): IO[UnknownHostException, InetSocketAddress] =
+    InetAddress.byName(hostname).flatMap(inetAddressEphemeral)
+
+  /**
+   * Creates a socket address from an IP address and a port number.
    */
   def inetAddress(address: InetAddress, port: Int): UIO[InetSocketAddress] =
     UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(address.jInetAddress, port)))
 
+  /**
+   * Creates a socket address from an IP address, with an ephemeral port.
+   */
   def inetAddressEphemeral(address: InetAddress): UIO[InetSocketAddress] = inetAddress(address, 0)
 
   /**
@@ -128,6 +160,12 @@ object InetSocketAddress {
   def unresolvedHostname(hostname: String, port: Int): UIO[InetSocketAddress] =
     UIO.effectTotal(new InetSocketAddress(JInetSocketAddress.createUnresolved(hostname, port)))
 
+  /**
+   * Creates an unresolved socket address from a hostname using an ephemeral port.
+   *
+   * No attempt will be made to resolve the hostname into an `InetAddress`.
+   * The socket address will be flagged as ''unresolved''.
+   */
   def unresolvedHostnameEphemeral(hostname: String): UIO[InetSocketAddress] = unresolvedHostname(hostname, 0)
 
 }

From 6f48c67b10f4693a2b0aaaaf2f282626f95cd168 Mon Sep 17 00:00:00 2001
From: Lachlan O'Dea <lodea@mac.com>
Date: Sat, 10 Oct 2020 15:34:56 +1100
Subject: [PATCH 3/7] Improvements to address handling.

---
 .../main/scala/zio/nio/core/InetAddress.scala |  2 +-
 .../zio/nio/core/InetSocketAddress.scala      |  2 +-
 .../nio/core/channels/DatagramChannel.scala   |  8 +--
 .../nio/core/channels/SelectableChannel.scala |  2 +-
 .../zio/nio/core/channels/SelectionKey.scala  | 15 ++++--
 .../nio/channels/AsynchronousChannel.scala    |  2 +-
 .../zio/nio/channels/DatagramChannel.scala    |  8 +--
 .../zio/nio/channels/SelectableChannel.scala  |  2 +-
 .../scala/zio/nio/channels/Selector.scala     | 43 +++++++++++++---
 .../scala/zio/nio/channels/SelectorSpec.scala | 51 +++++++++----------
 10 files changed, 86 insertions(+), 49 deletions(-)

diff --git a/nio-core/src/main/scala/zio/nio/core/InetAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetAddress.scala
index 3a901cf1..d62d64eb 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetAddress.scala
@@ -46,7 +46,7 @@ final class InetAddress private[nio] (private[nio] val jInetAddress: JInetAddres
 
   def canonicalHostName: String = jInetAddress.getCanonicalHostName
 
-  def address: Array[Byte] = jInetAddress.getAddress
+  def address: Chunk[Byte] = Chunk.fromArray(jInetAddress.getAddress)
 
   override def hashCode(): Int = jInetAddress.hashCode()
 
diff --git a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
index 095af550..e68f1478 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
@@ -9,7 +9,7 @@ import zio.{ IO, UIO }
  *
  * The concrete subclass [[InetSocketAddress]] is used in practice.
  */
-sealed class SocketAddress private[nio] (private[nio] val jSocketAddress: JSocketAddress) {
+sealed class SocketAddress protected (private[nio] val jSocketAddress: JSocketAddress) {
 
   final override def equals(obj: Any): Boolean =
     obj match {
diff --git a/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala b/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala
index 5a516699..5d5c20f0 100644
--- a/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala
+++ b/nio-core/src/main/scala/zio/nio/core/channels/DatagramChannel.scala
@@ -61,7 +61,7 @@ final class DatagramChannel private[channels] (override protected[channels] val
    * @return the local address if the socket is bound, otherwise `None`
    */
   def localAddress: IO[IOException, Option[SocketAddress]] =
-    IO.effect(channel.getLocalAddress()).refineToOrDie[IOException].map(a => Option(a).map(new SocketAddress(_)))
+    IO.effect(channel.getLocalAddress()).refineToOrDie[IOException].map(a => Option(a).map(SocketAddress.fromJava))
 
   /**
    * Receives a datagram via this channel into the given [[zio.nio.core.ByteBuffer]].
@@ -70,7 +70,9 @@ final class DatagramChannel private[channels] (override protected[channels] val
    * @return the socket address of the datagram's source, if available.
    */
   def receive(dst: ByteBuffer): IO[IOException, Option[SocketAddress]] =
-    IO.effect(channel.receive(dst.byteBuffer)).refineToOrDie[IOException].map(a => Option(a).map(new SocketAddress(_)))
+    IO.effect(channel.receive(dst.byteBuffer))
+      .refineToOrDie[IOException]
+      .map(a => Option(a).map(SocketAddress.fromJava))
 
   /**
    * Optionally returns the remote socket address that this channel's underlying socket is connected to.
@@ -78,7 +80,7 @@ final class DatagramChannel private[channels] (override protected[channels] val
    * @return the remote address if the socket is connected, otherwise `None`
    */
   def remoteAddress: IO[IOException, Option[SocketAddress]] =
-    IO.effect(channel.getRemoteAddress()).refineToOrDie[IOException].map(a => Option(a).map(new SocketAddress(_)))
+    IO.effect(channel.getRemoteAddress()).refineToOrDie[IOException].map(a => Option(a).map(SocketAddress.fromJava))
 
   /**
    * Sends a datagram via this channel to the given target [[zio.nio.core.SocketAddress]].
diff --git a/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala b/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala
index c694f168..7b9a51ee 100644
--- a/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala
+++ b/nio-core/src/main/scala/zio/nio/core/channels/SelectableChannel.scala
@@ -143,7 +143,7 @@ final class ServerSocketChannel(override protected val channel: JServerSocketCha
       })
 
   val localAddress: IO[IOException, SocketAddress] =
-    IO.effect(new SocketAddress(channel.getLocalAddress())).refineToOrDie[IOException]
+    IO.effect(SocketAddress.fromJava(channel.getLocalAddress())).refineToOrDie[IOException]
 }
 
 object ServerSocketChannel {
diff --git a/nio-core/src/main/scala/zio/nio/core/channels/SelectionKey.scala b/nio-core/src/main/scala/zio/nio/core/channels/SelectionKey.scala
index 62ddb1d7..67248a3d 100644
--- a/nio-core/src/main/scala/zio/nio/core/channels/SelectionKey.scala
+++ b/nio-core/src/main/scala/zio/nio/core/channels/SelectionKey.scala
@@ -56,8 +56,7 @@ final class SelectionKey(private[nio] val selectionKey: jc.SelectionKey) {
    * {{{
    *   for {
    *     _ <- selector.select
-   *     selectedKeys <- selector.selectedKeys
-   *     _ <- IO.foreach_(selectedKeys) { key =>
+   *     _ <- selector.foreachSelectedKey { key =>
    *       key.matchChannel { readyOps => {
    *         case channel: ServerSocketChannel if readyOps(Operation.Accept) =>
    *           // use `channel` to accept connection
@@ -68,7 +67,7 @@ final class SelectionKey(private[nio] val selectionKey: jc.SelectionKey) {
    *             IO.when(readyOps(Operation.Write)) {
    *               // use `channel` to write
    *             }
-   *       } } *> selector.removeKey(key)
+   *       } }
    *     }
    *   } yield ()
    * }}}
@@ -126,6 +125,14 @@ final class SelectionKey(private[nio] val selectionKey: jc.SelectionKey) {
 
   final def attachment: UIO[Option[AnyRef]] = IO.effectTotal(selectionKey.attachment()).map(Option(_))
 
-  override def toString: String = selectionKey.toString()
+  override def toString: String = selectionKey.toString
+
+  override def hashCode(): Int = selectionKey.hashCode()
+
+  override def equals(obj: Any): Boolean =
+    obj match {
+      case other: SelectionKey => selectionKey.equals(other.selectionKey)
+      case _                   => false
+    }
 
 }
diff --git a/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala b/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala
index 8fa283fa..41d2faaf 100644
--- a/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala
+++ b/nio/src/main/scala/zio/nio/channels/AsynchronousChannel.scala
@@ -106,7 +106,7 @@ class AsynchronousServerSocketChannel(private val channel: JAsynchronousServerSo
    */
   final def localAddress: IO[IOException, Option[SocketAddress]] =
     IO.effect(
-      Option(channel.getLocalAddress).map(new SocketAddress(_))
+      Option(channel.getLocalAddress).map(SocketAddress.fromJava)
     ).refineToOrDie[IOException]
 
   /**
diff --git a/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala b/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala
index 2fc56851..26e684db 100644
--- a/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala
+++ b/nio/src/main/scala/zio/nio/channels/DatagramChannel.scala
@@ -43,7 +43,7 @@ final class DatagramChannel private[channels] (override protected[channels] val
    * @return the local address if the socket is bound, otherwise `None`
    */
   def localAddress: IO[IOException, Option[SocketAddress]] =
-    IO.effect(channel.getLocalAddress()).refineToOrDie[IOException].map(a => Option(a).map(new SocketAddress(_)))
+    IO.effect(Option(channel.getLocalAddress()).map(SocketAddress.fromJava)).refineToOrDie[IOException]
 
   /**
    * Receives a datagram via this channel into the given [[zio.nio.core.ByteBuffer]].
@@ -52,7 +52,9 @@ final class DatagramChannel private[channels] (override protected[channels] val
    * @return the socket address of the datagram's source, if available.
    */
   def receive(dst: ByteBuffer): IO[IOException, Option[SocketAddress]] =
-    IO.effect(channel.receive(dst.byteBuffer)).refineToOrDie[IOException].map(a => Option(a).map(new SocketAddress(_)))
+    IO.effect(channel.receive(dst.byteBuffer))
+      .refineToOrDie[IOException]
+      .map(a => Option(a).map(SocketAddress.fromJava))
 
   /**
    * Optionally returns the remote socket address that this channel's underlying socket is connected to.
@@ -60,7 +62,7 @@ final class DatagramChannel private[channels] (override protected[channels] val
    * @return the remote address if the socket is connected, otherwise `None`
    */
   def remoteAddress: IO[IOException, Option[SocketAddress]] =
-    IO.effect(channel.getRemoteAddress()).refineToOrDie[IOException].map(a => Option(a).map(new SocketAddress(_)))
+    IO.effect(Option(channel.getRemoteAddress()).map(SocketAddress.fromJava)).refineToOrDie[IOException]
 
   /**
    * Sends a datagram via this channel to the given target [[zio.nio.core.SocketAddress]].
diff --git a/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala b/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala
index 1cb81935..fdc5d44e 100644
--- a/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala
+++ b/nio/src/main/scala/zio/nio/channels/SelectableChannel.scala
@@ -147,7 +147,7 @@ final class ServerSocketChannel private (override protected val channel: JServer
     IO.effect(Option(channel.accept()).map(new SocketChannel(_))).refineToOrDie[IOException]
 
   final val localAddress: IO[IOException, SocketAddress] =
-    IO.effect(new SocketAddress(channel.getLocalAddress())).refineToOrDie[IOException]
+    IO.effect(SocketAddress.fromJava(channel.getLocalAddress())).refineToOrDie[IOException]
 }
 
 object ServerSocketChannel {
diff --git a/nio/src/main/scala/zio/nio/channels/Selector.scala b/nio/src/main/scala/zio/nio/channels/Selector.scala
index aab6ac9f..eeda518c 100644
--- a/nio/src/main/scala/zio/nio/channels/Selector.scala
+++ b/nio/src/main/scala/zio/nio/channels/Selector.scala
@@ -1,16 +1,15 @@
 package zio.nio.channels
 
-import java.io.IOException
-import java.nio.channels.{ ClosedSelectorException, Selector => JSelector, SelectionKey => JSelectionKey }
-
-import zio.{ IO, Managed, UIO, ZIO }
 import com.github.ghik.silencer.silent
+import zio.blocking.Blocking
 import zio.duration.Duration
 import zio.nio.channels.spi.SelectorProvider
 import zio.nio.core.channels.SelectionKey
-import zio.blocking
-import zio.blocking.Blocking
+import zio.{ IO, Managed, UIO, ZIO, blocking }
 
+import java.io.IOException
+import java.nio.channels.{ ClosedSelectorException, SelectionKey => JSelectionKey, Selector => JSelector }
+import scala.collection.mutable
 import scala.jdk.CollectionConverters._
 
 class Selector(private[nio] val selector: JSelector) {
@@ -24,12 +23,40 @@ class Selector(private[nio] val selector: JSelector) {
       .map(_.asScala.toSet[JSelectionKey].map(new SelectionKey(_)))
       .refineToOrDie[ClosedSelectorException]
 
+  /**
+   * Returns this selector's selected-key set.
+   *
+   * Note that the returned set it mutable - keys may be removed from, but not directly added to it.
+   * Any attempt to add an object to the key set will cause an `UnsupportedOperationException` to be thrown.
+   * The selected-key set is not thread-safe.
+   */
   @silent
-  final val selectedKeys: IO[ClosedSelectorException, Set[SelectionKey]] =
+  final val selectedKeys: IO[ClosedSelectorException, mutable.Set[SelectionKey]] =
     IO.effect(selector.selectedKeys())
-      .map(_.asScala.toSet[JSelectionKey].map(new SelectionKey(_)))
+      .map(_.asScala.map(new SelectionKey(_)))
       .refineToOrDie[ClosedSelectorException]
 
+  /**
+   * Performs an effect with each selected key.
+   *
+   * If the result of effect is true, the key will be removed from the selected-key set, which is
+   * usually what you want after successfully handling a selected key.
+   */
+  def foreachSelectedKey[R, E](f: SelectionKey => ZIO[R, E, Boolean]): ZIO[R, E, Unit] =
+    ZIO.effectTotal(selector.selectedKeys().iterator()).flatMap { iter =>
+      def loop: ZIO[R, E, Unit] =
+        ZIO.effectSuspendTotal {
+          if (iter.hasNext) {
+            val key = iter.next()
+            f(new SelectionKey(key)).flatMap(ZIO.when(_)(ZIO.effectTotal(iter.remove()))) *>
+              loop
+          } else
+            ZIO.unit
+        }
+
+      loop
+    }
+
   final def removeKey(key: SelectionKey): IO[ClosedSelectorException, Unit] =
     IO.effect(selector.selectedKeys().remove(key.selectionKey))
       .unit
diff --git a/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala b/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala
index f04f9fe5..ef38585d 100644
--- a/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala
+++ b/nio/src/test/scala/zio/nio/channels/SelectorSpec.scala
@@ -38,32 +38,31 @@ object SelectorSpec extends BaseSpec {
       buffer: ByteBuffer
     ): ZIO[Blocking, Exception, Unit] =
       for {
-        _            <- selector.select
-        selectedKeys <- selector.selectedKeys
-        _            <- IO.foreach(selectedKeys) { key =>
-                          IO.whenM(safeStatusCheck(key.isAcceptable)) {
-                            for {
-                              clientOpt <- channel.accept
-                              client     = clientOpt.get
-                              _         <- client.configureBlocking(false)
-                              _         <- client.register(selector, Operation.Read)
-                            } yield ()
-                          } *>
-                            IO.whenM(safeStatusCheck(key.isReadable)) {
-                              IO.effectSuspendTotal {
-                                val sClient = key.channel
-                                val client  = sClient.asInstanceOf[zio.nio.core.channels.SocketChannel]
-                                for {
-                                  _ <- client.read(buffer)
-                                  _ <- buffer.flip
-                                  _ <- client.write(buffer)
-                                  _ <- buffer.clear
-                                  _ <- client.close
-                                } yield ()
-                              }
-                            } *>
-                            selector.removeKey(key)
-                        }
+        _ <- selector.select
+        _ <- selector.foreachSelectedKey { key =>
+               IO.whenM(safeStatusCheck(key.isAcceptable)) {
+                 for {
+                   clientOpt <- channel.accept
+                   client     = clientOpt.get
+                   _         <- client.configureBlocking(false)
+                   _         <- client.register(selector, Operation.Read)
+                 } yield ()
+               } *>
+                 IO.whenM(safeStatusCheck(key.isReadable)) {
+                   IO.effectSuspendTotal {
+                     val sClient = key.channel
+                     val client  = sClient.asInstanceOf[zio.nio.core.channels.SocketChannel]
+                     for {
+                       _ <- client.read(buffer)
+                       _ <- buffer.flip
+                       _ <- client.write(buffer)
+                       _ <- buffer.clear
+                       _ <- client.close
+                     } yield ()
+                   }
+                 }.as(true)
+             }
+        _ <- selector.selectedKeys.filterOrDieMessage(_.isEmpty)("Selected key set should be empty")
       } yield ()
 
     for {

From 918f97718562a9686b3a2c49c8b4328a621030f5 Mon Sep 17 00:00:00 2001
From: Lachlan O'Dea <lodea@mac.com>
Date: Mon, 26 Oct 2020 18:30:13 +1100
Subject: [PATCH 4/7] Add localhost constructor to InetSocketAddress.

---
 .../src/main/scala/zio/nio/core/InetSocketAddress.scala     | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
index e68f1478..74f4b70c 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
@@ -151,6 +151,12 @@ object InetSocketAddress {
    */
   def inetAddressEphemeral(address: InetAddress): UIO[InetSocketAddress] = inetAddress(address, 0)
 
+  /**
+   * Creates a socket address for localhost using the specified port.
+   */
+  def localHost(port: Int): IO[UnknownHostException, InetSocketAddress] =
+    InetAddress.localHost.flatMap(inetAddress(_, port))
+
   /**
    * Creates an unresolved socket address from a hostname and a port number.
    *

From fea81b8a4eb34839c29615c7a625a8febb3398b7 Mon Sep 17 00:00:00 2001
From: Steven Vroonland <steven@dataworkz.nl>
Date: Sat, 13 Mar 2021 12:42:36 +0100
Subject: [PATCH 5/7] Fix name conflict

---
 examples/src/main/scala/StreamsBasedServer.scala            | 2 +-
 .../src/main/scala/zio/nio/core/InetSocketAddress.scala     | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/examples/src/main/scala/StreamsBasedServer.scala b/examples/src/main/scala/StreamsBasedServer.scala
index a9282048..20413c0d 100644
--- a/examples/src/main/scala/StreamsBasedServer.scala
+++ b/examples/src/main/scala/StreamsBasedServer.scala
@@ -16,7 +16,7 @@ object StreamsBasedServer extends App {
     AsynchronousServerSocketChannel()
       .use(socket =>
         for {
-          _ <- InetSocketAddress.hostname("localhost", port).flatMap(socket.bindTo(_))
+          _ <- InetSocketAddress.hostName("localhost", port).flatMap(socket.bindTo(_))
           _ <- ZStream
                  .repeatEffect(socket.accept.preallocate)
                  .map(_.withEarlyRelease)
diff --git a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
index 74f4b70c..bd24e3e8 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
@@ -113,8 +113,8 @@ object InetSocketAddress {
    * This method will attempt to resolve the hostname; if this fails, the returned
    * socket address will be ''unresolved''.
    */
-  def hostname(hostname: String, port: Int): UIO[InetSocketAddress] =
-    UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(hostname, port)))
+  def hostName(hostName: String, port: Int): UIO[InetSocketAddress] =
+    UIO.effectTotal(new InetSocketAddress(new JInetSocketAddress(hostName, port)))
 
   /**
    * Creates a resolved socket address from a hostname and port number.
@@ -130,7 +130,7 @@ object InetSocketAddress {
    * This method will attempt to resolve the hostname; if this fails, the returned
    * socket address will be ''unresolved''.
    */
-  def hostnameEphemeral(hostname: String): UIO[InetSocketAddress] = this.hostname(hostname, 0)
+  def hostnameEphemeral(hostname: String): UIO[InetSocketAddress] = this.hostName(hostname, 0)
 
   /**
    * Creates a resolved socket address from a hostname, with an ephemeral port.

From cfc05506d5898e4c61c9ade047dad20a26ec2dba Mon Sep 17 00:00:00 2001
From: Steven Vroonland <steven@dataworkz.nl>
Date: Sat, 13 Mar 2021 12:43:10 +0100
Subject: [PATCH 6/7] Fix typo

---
 nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
index bd24e3e8..e16d7dfd 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
@@ -103,7 +103,7 @@ object InetSocketAddress {
    * Creates a socket address where the IP address is the wildcard address and
    * the port is ephemeral.
    *
-   * The socket address wll be ''resolved''.
+   * The socket address will be ''resolved''.
    */
   def wildCardEphemeral: UIO[InetSocketAddress] = wildCard(0)
 

From 8acdd43fc07d99dd316b64e233c5acebc4d582d8 Mon Sep 17 00:00:00 2001
From: Steven Vroonland <steven@dataworkz.nl>
Date: Sat, 13 Mar 2021 12:51:30 +0100
Subject: [PATCH 7/7] Consistent casing of hostName

---
 .../main/scala/zio/nio/core/InetAddress.scala    |  2 +-
 .../scala/zio/nio/core/InetSocketAddress.scala   | 16 ++++++++--------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/nio-core/src/main/scala/zio/nio/core/InetAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetAddress.scala
index d62d64eb..02cb3483 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetAddress.scala
@@ -42,7 +42,7 @@ final class InetAddress private[nio] (private[nio] val jInetAddress: JInetAddres
     IO.effect(jInetAddress.isReachable(networkInterface.jNetworkInterface, ttl, timeout))
       .refineToOrDie[IOException]
 
-  def hostname: String = jInetAddress.getHostName
+  def hostName: String = jInetAddress.getHostName
 
   def canonicalHostName: String = jInetAddress.getCanonicalHostName
 
diff --git a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
index e16d7dfd..e4a3e58b 100644
--- a/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
+++ b/nio-core/src/main/scala/zio/nio/core/InetSocketAddress.scala
@@ -121,8 +121,8 @@ object InetSocketAddress {
    *
    * If the hostname cannot be resolved, fails with `UnknownHostException`.
    */
-  def hostnameResolved(hostname: String, port: Int): IO[UnknownHostException, InetSocketAddress] =
-    InetAddress.byName(hostname).flatMap(inetAddress(_, port))
+  def hostNameResolved(hostName: String, port: Int): IO[UnknownHostException, InetSocketAddress] =
+    InetAddress.byName(hostName).flatMap(inetAddress(_, port))
 
   /**
    * Creates a socket address from a hostname, with an ephemeral port.
@@ -130,15 +130,15 @@ object InetSocketAddress {
    * This method will attempt to resolve the hostname; if this fails, the returned
    * socket address will be ''unresolved''.
    */
-  def hostnameEphemeral(hostname: String): UIO[InetSocketAddress] = this.hostName(hostname, 0)
+  def hostNameEphemeral(hostName: String): UIO[InetSocketAddress] = this.hostName(hostName, 0)
 
   /**
    * Creates a resolved socket address from a hostname, with an ephemeral port.
    *
    * If the hostname cannot be resolved, fails with `UnknownHostException`.
    */
-  def hostnameEphemeralResolved(hostname: String): IO[UnknownHostException, InetSocketAddress] =
-    InetAddress.byName(hostname).flatMap(inetAddressEphemeral)
+  def hostNameEphemeralResolved(hostName: String): IO[UnknownHostException, InetSocketAddress] =
+    InetAddress.byName(hostName).flatMap(inetAddressEphemeral)
 
   /**
    * Creates a socket address from an IP address and a port number.
@@ -163,8 +163,8 @@ object InetSocketAddress {
    * No attempt will be made to resolve the hostname into an `InetAddress`.
    * The socket address will be flagged as ''unresolved''.
    */
-  def unresolvedHostname(hostname: String, port: Int): UIO[InetSocketAddress] =
-    UIO.effectTotal(new InetSocketAddress(JInetSocketAddress.createUnresolved(hostname, port)))
+  def unresolvedHostName(hostName: String, port: Int): UIO[InetSocketAddress] =
+    UIO.effectTotal(new InetSocketAddress(JInetSocketAddress.createUnresolved(hostName, port)))
 
   /**
    * Creates an unresolved socket address from a hostname using an ephemeral port.
@@ -172,6 +172,6 @@ object InetSocketAddress {
    * No attempt will be made to resolve the hostname into an `InetAddress`.
    * The socket address will be flagged as ''unresolved''.
    */
-  def unresolvedHostnameEphemeral(hostname: String): UIO[InetSocketAddress] = unresolvedHostname(hostname, 0)
+  def unresolvedHostNameEphemeral(hostName: String): UIO[InetSocketAddress] = unresolvedHostName(hostName, 0)
 
 }