diff --git a/adafruit_httpserver/exceptions.py b/adafruit_httpserver/exceptions.py
new file mode 100644
index 0000000..ca70712
--- /dev/null
+++ b/adafruit_httpserver/exceptions.py
@@ -0,0 +1,52 @@
+# SPDX-FileCopyrightText: Copyright (c) 2022 Dan Halbert for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+"""
+`adafruit_httpserver.exceptions`
+====================================================
+* Author(s): Michał Pokusa
+"""
+
+
+class InvalidPathError(Exception):
+    """
+    Parent class for all path related errors.
+    """
+
+
+class ParentDirectoryReferenceError(InvalidPathError):
+    """
+    Path contains ``..``, a reference to the parent directory.
+    """
+
+    def __init__(self, path: str) -> None:
+        """Creates a new ``ParentDirectoryReferenceError`` for the ``path``."""
+        super().__init__(f"Parent directory reference in path: {path}")
+
+
+class BackslashInPathError(InvalidPathError):
+    """
+    Backslash ``\\`` in path.
+    """
+
+    def __init__(self, path: str) -> None:
+        """Creates a new ``BackslashInPathError`` for the ``path``."""
+        super().__init__(f"Backslash in path: {path}")
+
+
+class ResponseAlreadySentError(Exception):
+    """
+    Another ``HTTPResponse`` has already been sent. There can only be one per ``HTTPRequest``.
+    """
+
+
+class FileNotExistsError(Exception):
+    """
+    Raised when a file does not exist.
+    """
+
+    def __init__(self, path: str) -> None:
+        """
+        Creates a new ``FileNotExistsError`` for the file at ``path``.
+        """
+        super().__init__(f"File does not exist: {path}")
diff --git a/adafruit_httpserver/response.py b/adafruit_httpserver/response.py
index 19f69de..0444039 100644
--- a/adafruit_httpserver/response.py
+++ b/adafruit_httpserver/response.py
@@ -8,7 +8,7 @@
 """
 
 try:
-    from typing import Optional, Dict, Union, Tuple
+    from typing import Optional, Dict, Union, Tuple, Callable
     from socket import socket
     from socketpool import SocketPool
 except ImportError:
@@ -17,12 +17,33 @@
 import os
 from errno import EAGAIN, ECONNRESET
 
+from .exceptions import (
+    BackslashInPathError,
+    FileNotExistsError,
+    ParentDirectoryReferenceError,
+    ResponseAlreadySentError,
+)
 from .mime_type import MIMEType
 from .request import HTTPRequest
 from .status import HTTPStatus, CommonHTTPStatus
 from .headers import HTTPHeaders
 
 
+def _prevent_multiple_send_calls(function: Callable):
+    """
+    Decorator that prevents calling ``send`` or ``send_file`` more than once.
+    """
+
+    def wrapper(self: "HTTPResponse", *args, **kwargs):
+        if self._response_already_sent:  # pylint: disable=protected-access
+            raise ResponseAlreadySentError
+
+        result = function(self, *args, **kwargs)
+        return result
+
+    return wrapper
+
+
 class HTTPResponse:
     """
     Response to a given `HTTPRequest`. Use in `HTTPServer.route` decorator functions.
@@ -73,8 +94,8 @@ def route_func(request):
     """
     Defaults to ``text/plain`` if not set.
 
-    Can be explicitly provided in the constructor, in `send()` or
-    implicitly determined from filename in `send_file()`.
+    Can be explicitly provided in the constructor, in ``send()`` or
+    implicitly determined from filename in ``send_file()``.
 
     Common MIME types are defined in `adafruit_httpserver.mime_type.MIMEType`.
     """
@@ -94,7 +115,7 @@ def __init__(  # pylint: disable=too-many-arguments
         Sets `status`, ``headers`` and `http_version`
         and optionally default ``content_type``.
 
-        To send the response, call `send` or `send_file`.
+        To send the response, call ``send`` or ``send_file``.
         For chunked response use
         ``with HTTPRequest(request, content_type=..., chunked=True) as r:`` and `send_chunk`.
         """
@@ -115,7 +136,7 @@ def _send_headers(
     ) -> None:
         """
         Sends headers.
-        Implicitly called by `send` and `send_file` and in
+        Implicitly called by ``send`` and ``send_file`` and in
         ``with HTTPResponse(request, chunked=True) as response:`` context manager.
         """
         headers = self.headers.copy()
@@ -141,6 +162,7 @@ def _send_headers(
             self.request.connection, response_message_header.encode("utf-8")
         )
 
+    @_prevent_multiple_send_calls
     def send(
         self,
         body: str = "",
@@ -152,8 +174,6 @@ def send(
 
         Should be called **only once** per response.
         """
-        if self._response_already_sent:
-            raise RuntimeError("Response was already sent")
 
         if getattr(body, "encode", None):
             encoded_response_message_body = body.encode("utf-8")
@@ -167,12 +187,41 @@ def send(
         self._send_bytes(self.request.connection, encoded_response_message_body)
         self._response_already_sent = True
 
-    def send_file(
+    @staticmethod
+    def _check_file_path_is_valid(file_path: str) -> bool:
+        """
+        Checks if ``file_path`` is valid.
+        If not raises error corresponding to the problem.
+        """
+
+        # Check for backslashes
+        if "\\" in file_path:  # pylint: disable=anomalous-backslash-in-string
+            raise BackslashInPathError(file_path)
+
+        # Check each component of the path for parent directory references
+        for part in file_path.split("/"):
+            if part == "..":
+                raise ParentDirectoryReferenceError(file_path)
+
+    @staticmethod
+    def _get_file_length(file_path: str) -> int:
+        """
+        Tries to get the length of the file at ``file_path``.
+        Raises ``FileNotExistsError`` if file does not exist.
+        """
+        try:
+            return os.stat(file_path)[6]
+        except OSError:
+            raise FileNotExistsError(file_path)  # pylint: disable=raise-missing-from
+
+    @_prevent_multiple_send_calls
+    def send_file(  # pylint: disable=too-many-arguments
         self,
         filename: str = "index.html",
         root_path: str = "./",
         buffer_size: int = 1024,
         head_only: bool = False,
+        safe: bool = True,
     ) -> None:
         """
         Send response with content of ``filename`` located in ``root_path``.
@@ -181,17 +230,18 @@ def send_file(
 
         Should be called **only once** per response.
         """
-        if self._response_already_sent:
-            raise RuntimeError("Response was already sent")
+
+        if safe:
+            self._check_file_path_is_valid(filename)
 
         if not root_path.endswith("/"):
             root_path += "/"
-        try:
-            file_length = os.stat(root_path + filename)[6]
-        except OSError:
-            # If the file doesn't exist, return 404.
-            HTTPResponse(self.request, status=CommonHTTPStatus.NOT_FOUND_404).send()
-            return
+        if filename.startswith("/"):
+            filename = filename[1:]
+
+        full_file_path = root_path + filename
+
+        file_length = self._get_file_length(full_file_path)
 
         self._send_headers(
             content_type=MIMEType.from_file_name(filename),
@@ -199,7 +249,7 @@ def send_file(
         )
 
         if not head_only:
-            with open(root_path + filename, "rb") as file:
+            with open(full_file_path, "rb") as file:
                 while bytes_read := file.read(buffer_size):
                     self._send_bytes(self.request.connection, bytes_read)
         self._response_already_sent = True
diff --git a/adafruit_httpserver/server.py b/adafruit_httpserver/server.py
index 8e86e82..8662403 100644
--- a/adafruit_httpserver/server.py
+++ b/adafruit_httpserver/server.py
@@ -16,6 +16,7 @@
 
 from errno import EAGAIN, ECONNRESET, ETIMEDOUT
 
+from .exceptions import FileNotExistsError, InvalidPathError
 from .methods import HTTPMethod
 from .request import HTTPRequest
 from .response import HTTPResponse
@@ -26,18 +27,19 @@
 class HTTPServer:
     """A basic socket-based HTTP server."""
 
-    def __init__(self, socket_source: Protocol) -> None:
+    def __init__(self, socket_source: Protocol, root_path: str) -> None:
         """Create a server, and get it ready to run.
 
         :param socket: An object that is a source of sockets. This could be a `socketpool`
           in CircuitPython or the `socket` module in CPython.
+        :param str root_path: Root directory to serve files from
         """
         self._buffer = bytearray(1024)
         self._timeout = 1
         self.routes = _HTTPRoutes()
         self._socket_source = socket_source
         self._sock = None
-        self.root_path = "/"
+        self.root_path = root_path
 
     def route(self, path: str, method: HTTPMethod = HTTPMethod.GET) -> Callable:
         """
@@ -63,14 +65,13 @@ def route_decorator(func: Callable) -> Callable:
 
         return route_decorator
 
-    def serve_forever(self, host: str, port: int = 80, root_path: str = "") -> None:
+    def serve_forever(self, host: str, port: int = 80) -> None:
         """Wait for HTTP requests at the given host and port. Does not return.
 
         :param str host: host name or IP address
         :param int port: port
-        :param str root_path: root directory to serve files from
         """
-        self.start(host, port, root_path)
+        self.start(host, port)
 
         while True:
             try:
@@ -78,17 +79,14 @@ def serve_forever(self, host: str, port: int = 80, root_path: str = "") -> None:
             except OSError:
                 continue
 
-    def start(self, host: str, port: int = 80, root_path: str = "") -> None:
+    def start(self, host: str, port: int = 80) -> None:
         """
         Start the HTTP server at the given host and port. Requires calling
         poll() in a while loop to handle incoming requests.
 
         :param str host: host name or IP address
         :param int port: port
-        :param str root_path: root directory to serve files from
         """
-        self.root_path = root_path
-
         self._sock = self._socket_source.socket(
             self._socket_source.AF_INET, self._socket_source.SOCK_STREAM
         )
@@ -158,38 +156,50 @@ def poll(self):
                     conn, received_body_bytes, content_length
                 )
 
+                # Find a handler for the route
                 handler = self.routes.find_handler(
                     _HTTPRoute(request.path, request.method)
                 )
 
-                # If a handler for route exists and is callable, call it.
-                if handler is not None and callable(handler):
-                    handler(request)
-
-                # If no handler exists and request method is GET, try to serve a file.
-                elif handler is None and request.method in (
-                    HTTPMethod.GET,
-                    HTTPMethod.HEAD,
-                ):
-                    filename = "index.html" if request.path == "/" else request.path
-                    HTTPResponse(request).send_file(
-                        filename=filename,
-                        root_path=self.root_path,
-                        buffer_size=self.request_buffer_size,
-                        head_only=(request.method == HTTPMethod.HEAD),
+                try:
+                    # If a handler for route exists and is callable, call it.
+                    if handler is not None and callable(handler):
+                        handler(request)
+
+                    # If no handler exists and request method is GET or HEAD, try to serve a file.
+                    elif handler is None and request.method in (
+                        HTTPMethod.GET,
+                        HTTPMethod.HEAD,
+                    ):
+                        filename = "index.html" if request.path == "/" else request.path
+                        HTTPResponse(request).send_file(
+                            filename=filename,
+                            root_path=self.root_path,
+                            buffer_size=self.request_buffer_size,
+                            head_only=(request.method == HTTPMethod.HEAD),
+                        )
+                    else:
+                        HTTPResponse(
+                            request, status=CommonHTTPStatus.BAD_REQUEST_400
+                        ).send()
+
+                except InvalidPathError as error:
+                    HTTPResponse(request, status=CommonHTTPStatus.FORBIDDEN_403).send(
+                        str(error)
                     )
-                else:
-                    HTTPResponse(
-                        request, status=CommonHTTPStatus.BAD_REQUEST_400
-                    ).send()
-
-        except OSError as ex:
-            # handle EAGAIN and ECONNRESET
-            if ex.errno == EAGAIN:
-                # there is no data available right now, try again later.
+
+                except FileNotExistsError as error:
+                    HTTPResponse(request, status=CommonHTTPStatus.NOT_FOUND_404).send(
+                        str(error)
+                    )
+
+        except OSError as error:
+            # Handle EAGAIN and ECONNRESET
+            if error.errno == EAGAIN:
+                # There is no data available right now, try again later.
                 return
-            if ex.errno == ECONNRESET:
-                # connection reset by peer, try again later.
+            if error.errno == ECONNRESET:
+                # Connection reset by peer, try again later.
                 return
             raise
 
@@ -204,7 +214,7 @@ def request_buffer_size(self) -> int:
 
         Example::
 
-            server = HTTPServer(pool)
+            server = HTTPServer(pool, "/static")
             server.request_buffer_size = 2048
 
             server.serve_forever(str(wifi.radio.ipv4_address))
@@ -226,7 +236,7 @@ def socket_timeout(self) -> int:
 
         Example::
 
-            server = HTTPServer(pool)
+            server = HTTPServer(pool, "/static")
             server.socket_timeout = 3
 
             server.serve_forever(str(wifi.radio.ipv4_address))
diff --git a/adafruit_httpserver/status.py b/adafruit_httpserver/status.py
index d32538c..8a7b198 100644
--- a/adafruit_httpserver/status.py
+++ b/adafruit_httpserver/status.py
@@ -39,6 +39,9 @@ class CommonHTTPStatus(HTTPStatus):  # pylint: disable=too-few-public-methods
     BAD_REQUEST_400 = HTTPStatus(400, "Bad Request")
     """400 Bad Request"""
 
+    FORBIDDEN_403 = HTTPStatus(403, "Forbidden")
+    """403 Forbidden"""
+
     NOT_FOUND_404 = HTTPStatus(404, "Not Found")
     """404 Not Found"""
 
diff --git a/docs/api.rst b/docs/api.rst
index 4615507..64bb534 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -27,3 +27,6 @@
 
 .. automodule:: adafruit_httpserver.mime_type
     :members:
+
+.. automodule:: adafruit_httpserver.exceptions
+    :members:
diff --git a/examples/httpserver_chunked.py b/examples/httpserver_chunked.py
index ae519ec..ed67fc6 100644
--- a/examples/httpserver_chunked.py
+++ b/examples/httpserver_chunked.py
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Unlicense
 
-import secrets  # pylint: disable=no-name-in-module
+import os
 
 import socketpool
 import wifi
@@ -12,14 +12,15 @@
 from adafruit_httpserver.server import HTTPServer
 
 
-ssid, password = secrets.WIFI_SSID, secrets.WIFI_PASSWORD  # pylint: disable=no-member
+ssid = os.getenv("WIFI_SSID")
+password = os.getenv("WIFI_PASSWORD")
 
 print("Connecting to", ssid)
 wifi.radio.connect(ssid, password)
 print("Connected to", ssid)
 
 pool = socketpool.SocketPool(wifi.radio)
-server = HTTPServer(pool)
+server = HTTPServer(pool, "/static")
 
 
 @server.route("/chunked")
diff --git a/examples/httpserver_cpu_information.py b/examples/httpserver_cpu_information.py
index cf3d13b..41d7a05 100644
--- a/examples/httpserver_cpu_information.py
+++ b/examples/httpserver_cpu_information.py
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Unlicense
 
-import secrets  # pylint: disable=no-name-in-module
+import os
 
 import json
 import microcontroller
@@ -15,14 +15,15 @@
 from adafruit_httpserver.server import HTTPServer
 
 
-ssid, password = secrets.WIFI_SSID, secrets.WIFI_PASSWORD  # pylint: disable=no-member
+ssid = os.getenv("WIFI_SSID")
+password = os.getenv("WIFI_PASSWORD")
 
 print("Connecting to", ssid)
 wifi.radio.connect(ssid, password)
 print("Connected to", ssid)
 
 pool = socketpool.SocketPool(wifi.radio)
-server = HTTPServer(pool)
+server = HTTPServer(pool, "/static")
 
 
 @server.route("/cpu-information")
diff --git a/examples/httpserver_mdns.py b/examples/httpserver_mdns.py
index d2228c9..bebdc2a 100644
--- a/examples/httpserver_mdns.py
+++ b/examples/httpserver_mdns.py
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Unlicense
 
-import secrets  # pylint: disable=no-name-in-module
+import os
 
 import mdns
 import socketpool
@@ -14,7 +14,8 @@
 from adafruit_httpserver.server import HTTPServer
 
 
-ssid, password = secrets.WIFI_SSID, secrets.WIFI_PASSWORD  # pylint: disable=no-member
+ssid = os.getenv("WIFI_SSID")
+password = os.getenv("WIFI_PASSWORD")
 
 print("Connecting to", ssid)
 wifi.radio.connect(ssid, password)
@@ -25,7 +26,7 @@
 mdns_server.advertise_service(service_type="_http", protocol="_tcp", port=80)
 
 pool = socketpool.SocketPool(wifi.radio)
-server = HTTPServer(pool)
+server = HTTPServer(pool, "/static")
 
 
 @server.route("/")
diff --git a/examples/httpserver_neopixel.py b/examples/httpserver_neopixel.py
index 814a7af..baff3de 100644
--- a/examples/httpserver_neopixel.py
+++ b/examples/httpserver_neopixel.py
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Unlicense
 
-import secrets  # pylint: disable=no-name-in-module
+import os
 
 import board
 import neopixel
@@ -15,14 +15,15 @@
 from adafruit_httpserver.server import HTTPServer
 
 
-ssid, password = secrets.WIFI_SSID, secrets.WIFI_PASSWORD  # pylint: disable=no-member
+ssid = os.getenv("WIFI_SSID")
+password = os.getenv("WIFI_PASSWORD")
 
 print("Connecting to", ssid)
 wifi.radio.connect(ssid, password)
 print("Connected to", ssid)
 
 pool = socketpool.SocketPool(wifi.radio)
-server = HTTPServer(pool)
+server = HTTPServer(pool, "/static")
 
 pixel = neopixel.NeoPixel(board.NEOPIXEL, 1)
 
diff --git a/examples/httpserver_simple_poll.py b/examples/httpserver_simple_poll.py
index db876c4..1ed5027 100644
--- a/examples/httpserver_simple_poll.py
+++ b/examples/httpserver_simple_poll.py
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Unlicense
 
-import secrets  # pylint: disable=no-name-in-module
+import os
 
 import socketpool
 import wifi
@@ -13,14 +13,15 @@
 from adafruit_httpserver.server import HTTPServer
 
 
-ssid, password = secrets.WIFI_SSID, secrets.WIFI_PASSWORD  # pylint: disable=no-member
+ssid = os.getenv("WIFI_SSID")
+password = os.getenv("WIFI_PASSWORD")
 
 print("Connecting to", ssid)
 wifi.radio.connect(ssid, password)
 print("Connected to", ssid)
 
 pool = socketpool.SocketPool(wifi.radio)
-server = HTTPServer(pool)
+server = HTTPServer(pool, "/static")
 
 
 @server.route("/")
diff --git a/examples/httpserver_simple_serve.py b/examples/httpserver_simple_serve.py
index 632c234..226d8f2 100644
--- a/examples/httpserver_simple_serve.py
+++ b/examples/httpserver_simple_serve.py
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Unlicense
 
-import secrets  # pylint: disable=no-name-in-module
+import os
 
 import socketpool
 import wifi
@@ -13,14 +13,15 @@
 from adafruit_httpserver.server import HTTPServer
 
 
-ssid, password = secrets.WIFI_SSID, secrets.WIFI_PASSWORD  # pylint: disable=no-member
+ssid = os.getenv("WIFI_SSID")
+password = os.getenv("WIFI_PASSWORD")
 
 print("Connecting to", ssid)
 wifi.radio.connect(ssid, password)
 print("Connected to", ssid)
 
 pool = socketpool.SocketPool(wifi.radio)
-server = HTTPServer(pool)
+server = HTTPServer(pool, "/static")
 
 
 @server.route("/")
diff --git a/examples/httpserver_url_parameters.py b/examples/httpserver_url_parameters.py
index 2f95163..22f9f3b 100644
--- a/examples/httpserver_url_parameters.py
+++ b/examples/httpserver_url_parameters.py
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: Unlicense
 
-import secrets  # pylint: disable=no-name-in-module
+import os
 
 import socketpool
 import wifi
@@ -13,14 +13,15 @@
 from adafruit_httpserver.server import HTTPServer
 
 
-ssid, password = secrets.WIFI_SSID, secrets.WIFI_PASSWORD  # pylint: disable=no-member
+ssid = os.getenv("WIFI_SSID")
+password = os.getenv("WIFI_PASSWORD")
 
 print("Connecting to", ssid)
 wifi.radio.connect(ssid, password)
 print("Connected to", ssid)
 
 pool = socketpool.SocketPool(wifi.radio)
-server = HTTPServer(pool)
+server = HTTPServer(pool, "/static")
 
 
 class Device: