diff --git a/src/socketify/socketify.py b/src/socketify/socketify.py
index 1c4374e..c5918b7 100644
--- a/src/socketify/socketify.py
+++ b/src/socketify/socketify.py
@@ -240,6 +240,8 @@ def uws_generic_listen_handler(listen_socket, config, user_data):
         app = ffi.from_handle(user_data)
         if hasattr(app, "_listen_handler") and hasattr(app._listen_handler, '__call__'):
             app.socket = listen_socket
+            if listen_socket == ffi.NULL:
+                raise RuntimeError("Failed to listen on port %d" % int(config.port))
             app._listen_handler(None if config == ffi.NULL else AppListenOptions(port=int(config.port),host=None if config.host == ffi.NULL else ffi.string(config.host).decode("utf-8"), options=int(config.options)))
 
 @ffi.callback("void(uws_res_t *, void*)")
diff --git a/tests/async.py b/tests/examples/async.py
similarity index 81%
rename from tests/async.py
rename to tests/examples/async.py
index 1772074..f1adcdd 100644
--- a/tests/async.py
+++ b/tests/examples/async.py
@@ -8,7 +8,7 @@ async def delayed_hello(delay, res):
     res.end("Hello with delay!")
 
 def home(res, req):
-    #request objecy only lives during the live time of this call
+    #request object only lives during the life time of this call
     #get parameters, query, headers anything you need here
     delay = req.get_query("delay")
     delay = 0 if delay == None else float(delay)
@@ -16,15 +16,19 @@ def home(res, req):
     #abort handler is grabed here, so responses only will be send if res.aborted == False
     res.run_async(delayed_hello(delay, res))
 
-async def json_message(res, req):
+async def json(res, _):
     #req maybe will not be available in direct attached async functions
     #but if you dont care about req info you can do it
     await asyncio.sleep(2) #do something async
     res.write_header("Content-Type", "application/json")
     res.end({ "message": "I'm delayed!"})
 
+def not_found(res, req):
+    res.write_status(404).end("Not Found")
+
 app.get("/", home)
-app.get("/json_message", json_message)
+app.get("/json", json)
+app.any("/*", not_found)
 
 app.listen(3000, lambda config: print("Listening on port http://localhost:%s now\n" % str(config.port)))
 app.run()
\ No newline at end of file
diff --git a/tests/docker/pypy3/Dockerfile b/tests/examples/docker/pypy3/Dockerfile
similarity index 100%
rename from tests/docker/pypy3/Dockerfile
rename to tests/examples/docker/pypy3/Dockerfile
diff --git a/tests/docker/pypy3/main.py b/tests/examples/docker/pypy3/main.py
similarity index 100%
rename from tests/docker/pypy3/main.py
rename to tests/examples/docker/pypy3/main.py
diff --git a/tests/docker/pypy3/requirements.txt b/tests/examples/docker/pypy3/requirements.txt
similarity index 100%
rename from tests/docker/pypy3/requirements.txt
rename to tests/examples/docker/pypy3/requirements.txt
diff --git a/tests/docker/python3-alpine/Dockerfile b/tests/examples/docker/python3-alpine/Dockerfile
similarity index 100%
rename from tests/docker/python3-alpine/Dockerfile
rename to tests/examples/docker/python3-alpine/Dockerfile
diff --git a/tests/docker/python3-alpine/main.py b/tests/examples/docker/python3-alpine/main.py
similarity index 100%
rename from tests/docker/python3-alpine/main.py
rename to tests/examples/docker/python3-alpine/main.py
diff --git a/tests/docker/python3-alpine/requirements.txt b/tests/examples/docker/python3-alpine/requirements.txt
similarity index 100%
rename from tests/docker/python3-alpine/requirements.txt
rename to tests/examples/docker/python3-alpine/requirements.txt
diff --git a/tests/docker/python3/Dockerfile b/tests/examples/docker/python3/Dockerfile
similarity index 100%
rename from tests/docker/python3/Dockerfile
rename to tests/examples/docker/python3/Dockerfile
diff --git a/tests/docker/python3/main.py b/tests/examples/docker/python3/main.py
similarity index 100%
rename from tests/docker/python3/main.py
rename to tests/examples/docker/python3/main.py
diff --git a/tests/docker/python3/requirements.txt b/tests/examples/docker/python3/requirements.txt
similarity index 100%
rename from tests/docker/python3/requirements.txt
rename to tests/examples/docker/python3/requirements.txt
diff --git a/tests/shutdown.py b/tests/examples/graceful_shutdown.py
similarity index 100%
rename from tests/shutdown.py
rename to tests/examples/graceful_shutdown.py
diff --git a/tests/examples/not_found.py b/tests/examples/not_found.py
new file mode 100644
index 0000000..ef51983
--- /dev/null
+++ b/tests/examples/not_found.py
@@ -0,0 +1,24 @@
+from socketify import App, AppOptions, AppListenOptions
+
+app = App()
+
+def home(res, req):
+    res.end("Hello, World!")
+
+def user(res, req):
+    try:
+        if int(req.get_parameter(0)) == 1:
+            return res.end("Hello user 1!")
+    finally:
+        #invalid user tells to go, to the next route valid route (not found)
+        req.set_yield(1) 
+    
+def not_found(res, req):
+    res.write_status(404).end("Not Found")
+
+app.get("/", home)
+app.get("/user/:user_id", user)
+app.any("/*", not_found)
+
+app.listen(3000, lambda config: print("Listening on port http://localhost:%s now\n" % str(config.port)))
+app.run()
\ No newline at end of file