diff --git a/assets/opencomputers/lang/en_US.lang b/assets/opencomputers/lang/en_US.lang
index 5750508af..273cf59fa 100644
--- a/assets/opencomputers/lang/en_US.lang
+++ b/assets/opencomputers/lang/en_US.lang
@@ -56,6 +56,7 @@ oc:gui.Analyzer.RobotName=Name
 oc:gui.Analyzer.RobotOwner=Owner
 oc:gui.Analyzer.StoredEnergy=Stored energy
 oc:gui.Analyzer.TotalEnergy=Total stored energy
+oc:gui.Analyzer.Users=Users
 oc:gui.Robot.Power=Power
 oc:gui.Robot.TurnOff=Turn off
 oc:gui.Robot.TurnOn=Turn on
diff --git a/li/cil/oc/client/PacketHandler.scala b/li/cil/oc/client/PacketHandler.scala
index 4f902846c..12bec638e 100644
--- a/li/cil/oc/client/PacketHandler.scala
+++ b/li/cil/oc/client/PacketHandler.scala
@@ -26,6 +26,7 @@ class PacketHandler extends CommonPacketHandler {
       case PacketType.Analyze => onAnalyze(p)
       case PacketType.ChargerState => onChargerState(p)
       case PacketType.ComputerState => onComputerState(p)
+      case PacketType.ComputerUserList => onComputerUserList(p)
       case PacketType.PowerState => onPowerState(p)
       case PacketType.RedstoneState => onRedstoneState(p)
       case PacketType.RobotAnimateSwing => onRobotAnimateSwing(p)
@@ -73,6 +74,14 @@ class PacketHandler extends CommonPacketHandler {
       case _ => // Invalid packet.
     }
 
+  def onComputerUserList(p: PacketParser) =
+    p.readTileEntity[Computer]() match {
+      case Some(t) =>
+        val count = p.readInt()
+        t.users = (0 until count).map(_ => p.readUTF())
+      case _ => // Invalid packet.
+    }
+
   def onPowerState(p: PacketParser) =
     p.readTileEntity[PowerInformation]() match {
       case Some(t) =>
diff --git a/li/cil/oc/common/PacketType.scala b/li/cil/oc/common/PacketType.scala
index ad475fd25..d69894be9 100644
--- a/li/cil/oc/common/PacketType.scala
+++ b/li/cil/oc/common/PacketType.scala
@@ -6,6 +6,7 @@ object PacketType extends Enumeration {
   Analyze,
   ChargerState,
   ComputerState,
+  ComputerUserList,
   PowerState,
   RedstoneState,
   RobotAnimateSwing,
diff --git a/li/cil/oc/common/block/Case.scala b/li/cil/oc/common/block/Case.scala
index 2bbe5c748..f17c1e18f 100644
--- a/li/cil/oc/common/block/Case.scala
+++ b/li/cil/oc/common/block/Case.scala
@@ -80,8 +80,7 @@ abstract class Case(val parent: SimpleDelegator) extends Computer with SimpleDel
   // TODO do we have to manually sync the client since we can only check this on the server side?
   override def removedByEntity(world: World, x: Int, y: Int, z: Int, player: EntityPlayer) =
     world.getBlockTileEntity(x, y, z) match {
-      case c: tileentity.Case if !world.isRemote =>
-        c.computer.canInteract(player.getCommandSenderName)
+      case c: tileentity.Case => c.canInteract(player.getCommandSenderName)
       case _ => super.removedByEntity(world, x, y, z, player)
     }
 }
diff --git a/li/cil/oc/common/block/RobotAfterimage.scala b/li/cil/oc/common/block/RobotAfterimage.scala
index 3125f92ed..8402d08cd 100644
--- a/li/cil/oc/common/block/RobotAfterimage.scala
+++ b/li/cil/oc/common/block/RobotAfterimage.scala
@@ -54,7 +54,7 @@ class RobotAfterimage(val parent: SpecialDelegator) extends SpecialDelegate {
 
   override def rightClick(world: World, x: Int, y: Int, z: Int, player: EntityPlayer, side: ForgeDirection, hitX: Float, hitY: Float, hitZ: Float) = {
     findMovingRobot(world, x, y, z) match {
-      case Some(robot) => robot.getBlockType.onBlockActivated(world, robot.x, robot.y, robot.z, player, side.ordinal, hitX, hitY, hitZ)
+      case Some(robot) => Blocks.robotProxy.rightClick(world, robot.x, robot.y, robot.z, player, side, hitX, hitY, hitZ)
       case _ => world.setBlockToAir(x, y, z)
     }
   }
diff --git a/li/cil/oc/common/block/RobotProxy.scala b/li/cil/oc/common/block/RobotProxy.scala
index 1a8cd2a6f..8e6ed5e91 100644
--- a/li/cil/oc/common/block/RobotProxy.scala
+++ b/li/cil/oc/common/block/RobotProxy.scala
@@ -2,6 +2,7 @@ package li.cil.oc.common.block
 
 import java.util
 import li.cil.oc.common.{GuiType, tileentity}
+import li.cil.oc.server.PacketSender
 import li.cil.oc.server.component.robot
 import li.cil.oc.util.Tooltip
 import li.cil.oc.{Settings, OpenComputers}
@@ -84,6 +85,14 @@ class RobotProxy(val parent: SpecialDelegator) extends Computer with SpecialDele
                           side: ForgeDirection, hitX: Float, hitY: Float, hitZ: Float) = {
     if (!player.isSneaking) {
       if (!world.isRemote) {
+        // We only send slot changes to nearby players, so if there was no slot
+        // change since this player got into range he might have the wrong one,
+        // so we send him the current one just in case.
+        world.getBlockTileEntity(x, y, z) match {
+          case proxy: tileentity.RobotProxy =>
+            PacketSender.sendRobotSelectedSlotChange(proxy.robot)
+          case _ =>
+        }
         player.openGui(OpenComputers, GuiType.Robot.id, world, x, y, z)
       }
       true
diff --git a/li/cil/oc/common/tileentity/Computer.scala b/li/cil/oc/common/tileentity/Computer.scala
index 984a0a7ec..af64e6aac 100644
--- a/li/cil/oc/common/tileentity/Computer.scala
+++ b/li/cil/oc/common/tileentity/Computer.scala
@@ -6,9 +6,10 @@ import li.cil.oc.api.network._
 import li.cil.oc.server.{PacketSender => ServerPacketSender, driver, component}
 import li.cil.oc.util.ExtendedNBT._
 import net.minecraft.entity.player.EntityPlayer
-import net.minecraft.nbt.NBTTagCompound
+import net.minecraft.nbt.{NBTTagString, NBTTagCompound}
 import net.minecraftforge.common.ForgeDirection
 import scala.Some
+import scala.collection.mutable
 
 abstract class Computer(isRemote: Boolean) extends Environment with ComponentInventory with Rotatable with BundledRedstone with Analyzable {
   protected val _computer = if (isRemote) null else new component.Computer(this)
@@ -23,10 +24,14 @@ abstract class Computer(isRemote: Boolean) extends Environment with ComponentInv
 
   private var hasChanged = false
 
+  @SideOnly(Side.CLIENT)
+  private val _users = mutable.Set.empty[String]
+
   // ----------------------------------------------------------------------- //
 
   def isRunning = _isRunning
 
+  @SideOnly(Side.CLIENT)
   def isRunning_=(value: Boolean) = {
     _isRunning = value
     world.markBlockForRenderUpdate(x, y, z)
@@ -40,6 +45,21 @@ abstract class Computer(isRemote: Boolean) extends Environment with ComponentInv
     case _ => false
   }
 
+  def users: Iterable[String] =
+    if (isServer) computer.users
+    else _users
+
+  @SideOnly(Side.CLIENT)
+  def users_=(list: Iterable[String]) {
+    _users.clear()
+    _users ++= list
+  }
+
+  def canInteract(player: String) =
+    if (isServer) computer.canInteract(player)
+    else !Settings.get.canComputersBeOwned ||
+      _users.isEmpty || _users.contains(player)
+
   // ----------------------------------------------------------------------- //
 
   override def updateEntity() {
@@ -95,11 +115,14 @@ abstract class Computer(isRemote: Boolean) extends Environment with ComponentInv
   override def readFromNBTForClient(nbt: NBTTagCompound) {
     super.readFromNBTForClient(nbt)
     isRunning = nbt.getBoolean("isRunning")
+    _users.clear()
+    _users ++= nbt.getTagList("users").iterator[NBTTagString].map(_.data)
   }
 
   override def writeToNBTForClient(nbt: NBTTagCompound) {
     super.writeToNBTForClient(nbt)
     nbt.setBoolean("isRunning", isRunning)
+    nbt.setNewTagList("users", computer.users.map(user => new NBTTagString(null, user)))
   }
 
   // ----------------------------------------------------------------------- //
@@ -126,9 +149,14 @@ abstract class Computer(isRemote: Boolean) extends Environment with ComponentInv
 
   def onAnalyze(stats: NBTTagCompound, player: EntityPlayer, side: Int, hitX: Float, hitY: Float, hitZ: Float): Node = {
     if (computer != null) computer.lastError match {
-      case Some(value) => stats.setString(Settings.namespace + "gui.Analyzer.LastError", value)
+      case Some(value) =>
+        stats.setString(Settings.namespace + "gui.Analyzer.LastError", value)
       case _ =>
     }
+    val list = users
+    if (list.size > 0) {
+      stats.setString(Settings.namespace + "gui.Analyzer.Users", list.mkString(", "))
+    }
     computer.node
   }
 }
diff --git a/li/cil/oc/server/PacketSender.scala b/li/cil/oc/server/PacketSender.scala
index 36e833c87..3720be180 100644
--- a/li/cil/oc/server/PacketSender.scala
+++ b/li/cil/oc/server/PacketSender.scala
@@ -44,6 +44,16 @@ object PacketSender {
     }
   }
 
+  def sendComputerUserList(t: Computer, list: Array[String]) {
+    val pb = new PacketBuilder(PacketType.ComputerUserList)
+
+    pb.writeTileEntity(t)
+    pb.writeInt(list.length)
+    list.foreach(pb.writeUTF)
+
+    pb.sendToNearbyPlayers(t)
+  }
+
   def sendPowerState(t: PowerInformation, player: Option[Player] = None) {
     val pb = new PacketBuilder(PacketType.PowerState)
 
@@ -91,7 +101,7 @@ object PacketSender {
     pb.writeTileEntity(t.proxy)
     pb.writeInt(t.animationTicksTotal)
 
-    pb.sendToNearbyPlayers(t)
+    pb.sendToNearbyPlayers(t, 64)
   }
 
   def sendRobotAnimateTurn(t: Robot) {
@@ -101,7 +111,7 @@ object PacketSender {
     pb.writeByte(t.turnAxis)
     pb.writeInt(t.animationTicksTotal)
 
-    pb.sendToNearbyPlayers(t)
+    pb.sendToNearbyPlayers(t, 64)
   }
 
   def sendRobotEquippedItemChange(t: Robot, stack: ItemStack) {
@@ -119,7 +129,7 @@ object PacketSender {
     pb.writeTileEntity(t.proxy)
     pb.writeInt(t.selectedSlot)
 
-    pb.sendToNearbyPlayers(t)
+    pb.sendToNearbyPlayers(t, 16)
   }
 
   def sendRotatableState(t: Rotatable, player: Option[Player] = None) {
@@ -187,7 +197,7 @@ object PacketSender {
     pb.writeTileEntity(t)
     pb.writeBoolean(hasPower)
 
-    pb.sendToNearbyPlayers(t)
+    pb.sendToNearbyPlayers(t, 64)
   }
 
   def sendScreenResolutionChange(t: Buffer, w: Int, h: Int) {
diff --git a/li/cil/oc/server/component/Computer.scala b/li/cil/oc/server/component/Computer.scala
index 8cdef8dd7..8531c20c9 100644
--- a/li/cil/oc/server/component/Computer.scala
+++ b/li/cil/oc/server/component/Computer.scala
@@ -7,6 +7,7 @@ import li.cil.oc.api
 import li.cil.oc.api.network._
 import li.cil.oc.common.tileentity
 import li.cil.oc.server
+import li.cil.oc.server.PacketSender
 import li.cil.oc.util.ExtendedLuaState.extendLuaState
 import li.cil.oc.util.ExtendedNBT._
 import li.cil.oc.util.{ThreadPoolFactory, GameTimeFormatter, LuaStateFactory}
@@ -45,7 +46,7 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
 
   private val addedComponents = mutable.Set.empty[Component]
 
-  private val users = mutable.Set.empty[String]
+  private val _users = mutable.Set.empty[String]
 
   private val signals = new mutable.Queue[Computer.Signal]
 
@@ -67,6 +68,8 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
 
   private var remainingPause = 0 // Ticks left to wait before resuming.
 
+  private var usersChanged = false // Send updated users list to clients?
+
   private var message: Option[String] = None // For error messages.
 
   // ----------------------------------------------------------------------- //
@@ -83,6 +86,8 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
 
   def lastError = message
 
+  def users = _users.synchronized(_users.toArray)
+
   def isRobot = false
 
   // ----------------------------------------------------------------------- //
@@ -90,7 +95,7 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
   def address = node.address
 
   def canInteract(player: String) = !Settings.get.canComputersBeOwned ||
-    users.isEmpty || users.contains(player) ||
+    _users.synchronized(_users.isEmpty || _users.contains(player)) ||
     MinecraftServer.getServer.isSinglePlayer ||
     MinecraftServer.getServer.getConfigurationManager.isPlayerOpped(player)
 
@@ -232,6 +237,15 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
         }
     })
 
+    // Avoid spamming user list across the network.
+    if (worldTime % 20 == 0 && usersChanged) {
+      val list = _users.synchronized {
+        usersChanged = false
+        users
+      }
+      PacketSender.sendComputerUserList(owner, list)
+    }
+
     // Check if we should switch states. These are all the states in which we're
     // guaranteed that the executor thread isn't running anymore.
     state.synchronized(state.top match {
@@ -419,14 +433,14 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
 
   override def load(nbt: NBTTagCompound) = this.synchronized {
     assert(state.top == Computer.State.Stopped)
-    assert(users.isEmpty)
+    assert(_users.isEmpty)
     assert(signals.isEmpty)
     state.clear()
 
     super.load(nbt)
 
     state.pushAll(nbt.getTagList("state").iterator[NBTTagInt].reverse.map(s => Computer.State(s.data)))
-    nbt.getTagList("users").foreach[NBTTagString](u => users += u.data)
+    nbt.getTagList("users").foreach[NBTTagString](u => _users += u.data)
 
     if (state.size > 0 && state.top != Computer.State.Stopped && init()) {
       // Unlimit memory use while unpersisting.
@@ -506,7 +520,7 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
     processAddedComponents()
 
     nbt.setNewTagList("state", state.map(_.id))
-    nbt.setNewTagList("users", users)
+    nbt.setNewTagList("users", _users)
 
     if (state.top != Computer.State.Stopped) {
       // Unlimit memory while persisting.
@@ -826,25 +840,28 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
 
       // User management.
       lua.pushScalaFunction(lua => {
-        users.foreach(lua.pushString)
-        users.size
+        _users.foreach(lua.pushString)
+        _users.size
       })
       lua.setField(-2, "users")
 
       lua.pushScalaFunction(lua => try {
-        if (users.size >= Settings.get.maxUsers)
+        if (_users.size >= Settings.get.maxUsers)
           throw new Exception("too many users")
 
         val name = lua.checkString(1)
 
-        if (users.contains(name))
+        if (_users.contains(name))
           throw new Exception("user exists")
         if (name.length > Settings.get.maxUsernameLength)
           throw new Exception("username too long")
         if (!MinecraftServer.getServer.getConfigurationManager.getAllUsernames.contains(name))
           throw new Exception("player must be online")
 
-        users += name
+        _users.synchronized {
+          _users += name
+          usersChanged = true
+        }
         lua.pushBoolean(true)
         1
       } catch {
@@ -857,7 +874,13 @@ class Computer(val owner: tileentity.Computer) extends ManagedComponent with Con
 
       lua.pushScalaFunction(lua => {
         val name = lua.checkString(1)
-        lua.pushBoolean(users.remove(name))
+        _users.synchronized {
+          val success = _users.remove(name)
+          if (success) {
+            usersChanged = true
+          }
+          lua.pushBoolean(success)
+        }
         1
       })
       lua.setField(-2, "removeUser")
diff --git a/li/cil/oc/server/component/ManagedComponent.scala b/li/cil/oc/server/component/ManagedComponent.scala
index 98030d27f..e1657d522 100644
--- a/li/cil/oc/server/component/ManagedComponent.scala
+++ b/li/cil/oc/server/component/ManagedComponent.scala
@@ -22,15 +22,6 @@ abstract class ManagedComponent extends ManagedEnvironment {
     if (node != null) nbt.setNewCompoundTag("node", node.save)
   }
 
-  /**
-   * Handy function for returning a list of results.
-   * <p/>
-   * This is primarily meant to be used for returning result arrays from Lua
-   * callbacks, to avoid having to write `XYZ.box(...)` all the time.
-   *
-   * @param args the values to return.
-   * @return and array of objects.
-   */
   final protected def result(args: Any*): Array[AnyRef] = {
     def unwrap(arg: Any): AnyRef = arg match {
       case x: ScalaNumber => x.underlying