diff --git a/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/SonosLibrary.kt b/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/SonosLibrary.kt
index 31cc4e2..4fe214d 100644
--- a/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/SonosLibrary.kt
+++ b/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/SonosLibrary.kt
@@ -9,19 +9,6 @@ import org.luaj.vm2.lib.TwoArgFunction
 import org.luaj.vm2.lib.ZeroArgFunction
 import org.luaj.vm2.lib.jse.CoerceJavaToLua
 
-class OfFunction : OneArgFunction() {
-   override fun call(ip: LuaValue): LuaValue =
-      CoerceJavaToLua.coerce(SonosDevice(ip.checkjstring()))
-}
-
-class DiscoverFunction : ZeroArgFunction() {
-   override fun call(): LuaTable = LuaValue.tableOf().also { devices ->
-      SonosDiscovery.discover()
-         .map { CoerceJavaToLua.coerce(it) }
-         .forEachIndexed { i, device -> devices.set(i + 1, device) }
-   }
-}
-
 class SonosLibrary : TwoArgFunction() {
 
    override fun call(modname: LuaValue, env: LuaValue): LuaValue {
@@ -34,4 +21,17 @@ class SonosLibrary : TwoArgFunction() {
 
       return LuaValue.NIL
    }
+
+   class OfFunction : OneArgFunction() {
+      override fun call(ip: LuaValue): LuaValue =
+         CoerceJavaToLua.coerce(SonosDevice(ip.checkjstring()))
+   }
+
+   class DiscoverFunction : ZeroArgFunction() {
+      override fun call(): LuaTable = LuaValue.tableOf().also { devices ->
+         SonosDiscovery.discover()
+            .map { CoerceJavaToLua.coerce(it) }
+            .forEachIndexed { i, device -> devices.set(i + 1, device) }
+      }
+   }
 }
\ No newline at end of file
diff --git a/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/UtilLibrary.kt b/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/UtilLibrary.kt
new file mode 100644
index 0000000..a0e88cf
--- /dev/null
+++ b/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/lib/UtilLibrary.kt
@@ -0,0 +1,20 @@
+package com.bartlomiejpluta.ttsserver.core.lua.lib
+
+import org.luaj.vm2.LuaValue
+import org.luaj.vm2.lib.OneArgFunction
+import org.luaj.vm2.lib.TwoArgFunction
+
+class UtilLibrary : TwoArgFunction() {
+   override fun call(modname: LuaValue, env: LuaValue): LuaValue {
+      env.set("sleep", SleepFunction())
+
+      return LuaValue.NIL
+   }
+
+   class SleepFunction : OneArgFunction() {
+      override fun call(ms: LuaValue): LuaValue {
+         Thread.sleep(ms.checklong())
+         return LuaValue.NIL
+      }
+   }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/sandbox/SandboxFactory.kt b/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/sandbox/SandboxFactory.kt
index 16cec1e..2a16077 100644
--- a/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/sandbox/SandboxFactory.kt
+++ b/app/src/main/java/com/bartlomiejpluta/ttsserver/core/lua/sandbox/SandboxFactory.kt
@@ -3,6 +3,7 @@ package com.bartlomiejpluta.ttsserver.core.lua.sandbox
 import com.bartlomiejpluta.ttsserver.core.lua.lib.HTTPLibrary
 import com.bartlomiejpluta.ttsserver.core.lua.lib.SonosLibrary
 import com.bartlomiejpluta.ttsserver.core.lua.lib.TTSLibrary
+import com.bartlomiejpluta.ttsserver.core.lua.lib.UtilLibrary
 import org.luaj.vm2.Globals
 import org.luaj.vm2.LoadState
 import org.luaj.vm2.compiler.LuaC
@@ -14,6 +15,7 @@ import org.luaj.vm2.lib.jse.JseMathLib
 import org.luaj.vm2.lib.jse.JseOsLib
 
 class SandboxFactory(
+   private val utilLibrary: UtilLibrary,
    private val httpLibrary: HTTPLibrary,
    private val ttsLibrary: TTSLibrary,
    private val sonosLibrary: SonosLibrary
@@ -25,6 +27,7 @@ class SandboxFactory(
       it.load(StringLib())
       it.load(JseMathLib())
       it.load(JseOsLib())
+      it.load(utilLibrary)
       it.load(httpLibrary)
       it.load(ttsLibrary)
       it.load(sonosLibrary)
diff --git a/app/src/main/java/com/bartlomiejpluta/ttsserver/di/module/LuaModule.kt b/app/src/main/java/com/bartlomiejpluta/ttsserver/di/module/LuaModule.kt
index 04288be..ce14347 100644
--- a/app/src/main/java/com/bartlomiejpluta/ttsserver/di/module/LuaModule.kt
+++ b/app/src/main/java/com/bartlomiejpluta/ttsserver/di/module/LuaModule.kt
@@ -4,6 +4,7 @@ import android.content.Context
 import com.bartlomiejpluta.ttsserver.core.lua.lib.HTTPLibrary
 import com.bartlomiejpluta.ttsserver.core.lua.lib.SonosLibrary
 import com.bartlomiejpluta.ttsserver.core.lua.lib.TTSLibrary
+import com.bartlomiejpluta.ttsserver.core.lua.lib.UtilLibrary
 import com.bartlomiejpluta.ttsserver.core.lua.loader.EndpointLoader
 import com.bartlomiejpluta.ttsserver.core.lua.sandbox.SandboxFactory
 import com.bartlomiejpluta.ttsserver.core.tts.engine.TTSEngine
@@ -21,8 +22,17 @@ class LuaModule {
 
    @Provides
    @Singleton
-   fun sandboxFactory(httpLibrary: HTTPLibrary, ttsLibrary: TTSLibrary, sonosLibrary: SonosLibrary) =
-      SandboxFactory(httpLibrary, ttsLibrary, sonosLibrary)
+   fun sandboxFactory(
+      utilLibrary: UtilLibrary,
+      httpLibrary: HTTPLibrary,
+      ttsLibrary: TTSLibrary,
+      sonosLibrary: SonosLibrary
+   ) =
+      SandboxFactory(utilLibrary, httpLibrary, ttsLibrary, sonosLibrary)
+
+   @Provides
+   @Singleton
+   fun extraLibrary() = UtilLibrary()
 
    @Provides
    @Singleton
diff --git a/app/src/main/java/com/bartlomiejpluta/ttsserver/ui/main/MainActivity.kt b/app/src/main/java/com/bartlomiejpluta/ttsserver/ui/main/MainActivity.kt
index c16b797..1e107e3 100644
--- a/app/src/main/java/com/bartlomiejpluta/ttsserver/ui/main/MainActivity.kt
+++ b/app/src/main/java/com/bartlomiejpluta/ttsserver/ui/main/MainActivity.kt
@@ -114,4 +114,4 @@ class MainActivity : DaggerAppCompatActivity() {
          startService(it)
       }
    }
-}
+}
\ No newline at end of file