serving.py

# -*- coding: utf-8 -*-
"""
    werkzeug.serving
    ~~~~~~~~~~~~~~~~

    There are many ways to serve a WSGI application.  While you're developing
    it you usually don't want a full blown webserver like Apache but a simple
    standalone one.  From Python 2.5 onwards there is the `wsgiref`_ server in
    the standard library.  If you're using older versions of Python you can
    download the package from the cheeseshop.

    However there are some caveats. Sourcecode won't reload itself when
    changed and each time you kill the server using ``^C`` you get an
    `KeyboardInterrupt` error.  While the latter is easy to solve the first
    one can be a pain in the ass in some situations.

    The easiest way is creating a small ``start-myproject.py`` that runs the
    application::

        #!/usr/bin/env python
        # -*- coding: utf-8 -*-
        from myproject import make_app
        from werkzeug.serving import run_simple

        app = make_app(...)
        run_simple('localhost', 8080, app, use_reloader=True)

    You can also pass it a `extra_files` keyword argument with a list of
    additional files (like configuration files) you want to observe.

    For bigger applications you should consider using `click`
    (http://click.pocoo.org) instead of a simple start file.


    :copyright: 2007 Pallets
    :license: BSD-3-Clause
"""
import io
import os
import signal
import socket
import sys

from ._compat import PY2
from ._compat import reraise
from ._compat import WIN
from ._compat import wsgi_encoding_dance
from ._internal import _log
from .exceptions import InternalServerError
from .urls import uri_to_iri
from .urls import url_parse
from .urls import url_unquote

try:
    import socketserver
    from http.server import BaseHTTPRequestHandler
    from http.server import HTTPServer
except ImportError:
    import SocketServer as socketserver
    from BaseHTTPServer import HTTPServer
    from BaseHTTPServer import BaseHTTPRequestHandler

try:
    import ssl
except ImportError:

    class _SslDummy(object):
        def __getattr__(self, name):
            raise RuntimeError("SSL support unavailable")

    ssl = _SslDummy()

try:
    import termcolor
except ImportError:
    termcolor = None


def _get_openssl_crypto_module():
    try:
        from OpenSSL import crypto
    except ImportError:
        raise TypeError("Using ad-hoc certificates requires the pyOpenSSL library.")
    else:
        return crypto


ThreadingMixIn = socketserver.ThreadingMixIn
can_fork = hasattr(os, "fork")

if can_fork:
    ForkingMixIn = socketserver.ForkingMixIn
else:

    class ForkingMixIn(object):
        pass


try:
    af_unix = socket.AF_UNIX
except AttributeError:
    af_unix = None


LISTEN_QUEUE = 128
can_open_by_fd = not WIN and hasattr(socket, "fromfd")

# On Python 3, ConnectionError represents the same errnos as
# socket.error from Python 2, while socket.error is an alias for the
# more generic OSError.
if PY2:
    _ConnectionError = socket.error
else:
    _ConnectionError = ConnectionError


class DechunkedInput(io.RawIOBase):
    """An input stream that handles Transfer-Encoding 'chunked'"""

    def __init__(self, rfile):
        self._rfile = rfile
        self._done = False
        self._len = 0

    def readable(self):
        return True

    def read_chunk_len(self):
        try:
            line = self._rfile.readline().decode("latin1")
            _len = int(line.strip(), 16)
        except ValueError:
            raise IOError("Invalid chunk header")
        if _len < 0:
            raise IOError("Negative chunk length not allowed")
        return _len

    def readinto(self, buf):
        read = 0
        while not self._done and read < len(buf):
            if self._len == 0:
                # This is the first chunk or we fully consumed the previous
                # one. Read the next length of the next chunk
                self._len = self.read_chunk_len()

            if self._len == 0:
                # Found the final chunk of size 0. The stream is now exhausted,
                # but there is still a final newline that should be consumed
                self._done = True

            if self._len > 0:
                # There is data (left) in this chunk, so append it to the
                # buffer. If this operation fully consumes the chunk, this will
                # reset self._len to 0.
                n = min(len(buf), self._len)
                buf[read : read + n] = self._rfile.read(n)
                self._len -= n
                read += n

            if self._len == 0:
                # Skip the terminating newline of a chunk that has been fully
                # consumed. This also applies to the 0-sized final chunk
                terminator = self._rfile.readline()
                if terminator not in (b"\n", b"\r\n", b"\r"):
                    raise IOError("Missing chunk terminating newline")

        return read


class WSGIRequestHandler(BaseHTTPRequestHandler, object):

    """A request handler that implements WSGI dispatching."""

    @property
    def server_version(self):
        from . import __version__

        return "Werkzeug/" + __version__

    def make_environ(self):
        request_url = url_parse(self.path)

        def shutdown_server():
            self.server.shutdown_signal = True

        url_scheme = "http" if self.server.ssl_context is None else "https"
        if not self.client_address:
            self.client_address = "<local>"
        if isinstance(self.client_address, str):
            self.client_address = (self.client_address, 0)
        else:
            pass
        path_info = url_unquote(request_url.path)

        environ = {
            "wsgi.version": (1, 0),
            "wsgi.url_scheme": url_scheme,
            "wsgi.input": self.rfile,
            "wsgi.errors": sys.stderr,
            "wsgi.multithread": self.server.multithread,
            "wsgi.multiprocess": self.server.multiprocess,
            "wsgi.run_once": False,
            "werkzeug.server.shutdown": shutdown_server,
            "SERVER_SOFTWARE": self.server_version,
            "REQUEST_METHOD": self.command,
            "SCRIPT_NAME": "",
            "PATH_INFO": wsgi_encoding_dance(path_info),
            "QUERY_STRING": wsgi_encoding_dance(request_url.query),
            # Non-standard, added by mod_wsgi, uWSGI
            "REQUEST_URI": wsgi_encoding_dance(self.path),
            # Non-standard, added by gunicorn
            "RAW_URI": wsgi_encoding_dance(self.path),
            "REMOTE_ADDR": self.address_string(),
            "REMOTE_PORT": self.port_integer(),
            "SERVER_NAME": self.server.server_address[0],
            "SERVER_PORT": str(self.server.server_address[1]),
            "SERVER_PROTOCOL": self.request_version,
        }

        for key, value in self.get_header_items():
            key = key.upper().replace("-", "_")
            value = value.replace("\r\n", "")
            if key not in ("CONTENT_TYPE", "CONTENT_LENGTH"):
                key = "HTTP_" + key
                if key in environ:
                    value = "{},{}".format(environ[key], value)
            environ[key] = value

        if environ.get("HTTP_TRANSFER_ENCODING", "").strip().lower() == "chunked":
            environ["wsgi.input_terminated"] = True
            environ["wsgi.input"] = DechunkedInput(environ["wsgi.input"])

        if request_url.scheme and request_url.netloc:
            environ["HTTP_HOST"] = request_url.netloc

        return environ

    def run_wsgi(self):
        if self.headers.get("Expect", "").lower().strip() == "100-continue":
            self.wfile.write(b"HTTP/1.1 100 Continue\r\n\r\n")

        self.environ = environ = self.make_environ()
        headers_set = []
        headers_sent = []

        def write(data):
            assert headers_set, "write() before start_response"
            if not headers_sent:
                status, response_headers = headers_sent[:] = headers_set
                try:
                    code, msg = status.split(None, 1)
                except ValueError:
                    code, msg = status, ""
                code = int(code)
                self.send_response(code, msg)
                header_keys = set()
                for key, value in response_headers:
                    self.send_header(key, value)
                    key = key.lower()
                    header_keys.add(key)
                if not (
                    "content-length" in header_keys
                    or environ["REQUEST_METHOD"] == "HEAD"
                    or code < 200
                    or code in (204, 304)
                ):
                    self.close_connection = True
                    self.send_header("Connection", "close")
                if "server" not in header_keys:
                    self.send_header("Server", self.version_string())
                if "date" not in header_keys:
                    self.send_header("Date", self.date_time_string())
                self.end_headers()

            assert isinstance(data, bytes), "applications must write bytes"
            if data:
                # Only write data if there is any to avoid Python 3.5 SSL bug
                self.wfile.write(data)
            self.wfile.flush()

        def start_response(status, response_headers, exc_info=None):
            if exc_info:
                try:
                    if headers_sent:
                        reraise(*exc_info)
                finally:
                    exc_info = None
            elif headers_set:
                raise AssertionError("Headers already set")
            headers_set[:] = [status, response_headers]
            return write

        def execute(app):
            application_iter = app(environ, start_response)
            try:
                for data in application_iter:
                    write(data)
                if not headers_sent:
                    write(b"")
            finally:
                if hasattr(application_iter, "close"):
                    application_iter.close()
                application_iter = None

        try:
            execute(self.server.app)
        except (_ConnectionError, socket.timeout) as e:
            self.connection_dropped(e, environ)
        except Exception:
            if self.server.passthrough_errors:
                raise
            from .debug.tbtools import get_current_traceback

            traceback = get_current_traceback(ignore_system_exceptions=True)
            try:
                # if we haven't yet sent the headers but they are set
                # we roll back to be able to set them again.
                if not headers_sent:
                    del headers_set[:]
                execute(InternalServerError())
            except Exception:
                pass
            self.server.log("error", "Error on request:\n%s", traceback.plaintext)

    def handle(self):
        """Handles a request ignoring dropped connections."""
        rv = None
        try:
            rv = BaseHTTPRequestHandler.handle(self)
        except (_ConnectionError, socket.timeout) as e:
            self.connection_dropped(e)
        except Exception as e:
            if self.server.ssl_context is None or not is_ssl_error(e):
                raise
        if self.server.shutdown_signal:
            self.initiate_shutdown()
        return rv

    def initiate_shutdown(self):
        """A horrible, horrible way to kill the server for Python 2.6 and
        later.  It's the best we can do.
        """
        # Windows does not provide SIGKILL, go with SIGTERM then.
        sig = getattr(signal, "SIGKILL", signal.SIGTERM)
        # reloader active
        if is_running_from_reloader():
            os.kill(os.getpid(), sig)
        # python 2.7
        self.server._BaseServer__shutdown_request = True
        # python 2.6
        self.server._BaseServer__serving = False

    def connection_dropped(self, error, environ=None):
        """Called if the connection was closed by the client.  By default
        nothing happens.
        """

    def handle_one_request(self):
        """Handle a single HTTP request."""
        self.raw_requestline = self.rfile.readline()
        if not self.raw_requestline:
            self.close_connection = 1
        elif self.parse_request():
            return self.run_wsgi()

    def send_response(self, code, message=None):
        """Send the response header and log the response code."""
        self.log_request(code)
        if message is None:
            message = code in self.responses and self.responses[code][0] or ""
        if self.request_version != "HTTP/0.9":
            hdr = "%s %d %s\r\n" % (self.protocol_version, code, message)
            self.wfile.write(hdr.encode("ascii"))

    def version_string(self):
        return BaseHTTPRequestHandler.version_string(self).strip()

    def address_string(self):
        if getattr(self, "environ", None):
            return self.environ["REMOTE_ADDR"]
        elif not self.client_address:
            return "<local>"
        elif isinstance(self.client_address, str):
            return self.client_address
        else:
            return self.client_address[0]

    def port_integer(self):
        return self.client_address[1]

    def log_request(self, code="-", size="-"):
        try:
            path = uri_to_iri(self.path)
            msg = "%s %s %s" % (self.command, path, self.request_version)
        except AttributeError:
            # path isn't set if the requestline was bad
            msg = self.requestline

        code = str(code)

        if termcolor:
            color = termcolor.colored

            if code[0] == "1":  # 1xx - Informational
                msg = color(msg, attrs=["bold"])
            elif code[0] == "2":  # 2xx - Success
                msg = color(msg, color="white")
            elif code == "304":  # 304 - Resource Not Modified
                msg = color(msg, color="cyan")
            elif code[0] == "3":  # 3xx - Redirection
                msg = color(msg, color="green")
            elif code == "404":  # 404 - Resource Not Found
                msg = color(msg, color="yellow")
            elif code[0] == "4":  # 4xx - Client Error
                msg = color(msg, color="red", attrs=["bold"])
            else:  # 5xx, or any other response
                msg = color(msg, color="magenta", attrs=["bold"])

        self.log("info", '"%s" %s %s', msg, code, size)

    def log_error(self, *args):
        self.log("error", *args)

    def log_message(self, format, *args):
        self.log("info", format, *args)

    def log(self, type, message, *args):
        _log(
            type,
            "%s - - [%s] %s\n"
            % (self.address_string(), self.log_date_time_string(), message % args),
        )

    def get_header_items(self):
        """
        Get an iterable list of key/value pairs representing headers.

        This function provides Python 2/3 compatibility as related to the
        parsing of request headers. Python 2.7 is not compliant with
        RFC 3875 Section 4.1.18 which requires multiple values for headers
        to be provided or RFC 2616 which allows for folding of multi-line
        headers. This function will return a matching list regardless
        of Python version. It can be removed once Python 2.7 support
        is dropped.

        :return: List of tuples containing header hey/value pairs
        """
        if PY2:
            # For Python 2, process the headers manually according to
            # W3C RFC 2616 Section 4.2.
            items = []
            for header in self.headers.headers:
                # Remove "\r\n" from the header and split on ":" to get
                # the field name and value.
                try:
                    key, value = header[0:-2].split(":", 1)
                except ValueError:
                    # If header could not be slit with : but starts with white
                    # space and it follows an existing header, it's a folded
                    # header.
                    if header[0] in ("\t", " ") and items:
                        # Pop off the last header
                        key, value = items.pop()
                        # Append the current header to the value of the last
                        # header which will be placed back on the end of the
                        # list
                        value = value + header
                    # Otherwise it's just a bad header and should error
                    else:
                        # Re-raise the value error
                        raise

                # Add the key and the value once stripped of leading
                # white space. The specification allows for stripping
                # trailing white space but the Python 3 code does not
                # strip trailing white space. Therefore, trailing space
                # will be left as is to match the Python 3 behavior.
                items.append((key, value.lstrip()))
        else:
            items = self.headers.items()

        return items


#: backwards compatible name if someone is subclassing it
BaseRequestHandler = WSGIRequestHandler


def generate_adhoc_ssl_pair(cn=None):
    from random import random

    crypto = _get_openssl_crypto_module()

    # pretty damn sure that this is not actually accepted by anyone
    if cn is None:
        cn = "*"

    cert = crypto.X509()
    cert.set_serial_number(int(random() * sys.maxsize))
    cert.gmtime_adj_notBefore(0)
    cert.gmtime_adj_notAfter(60 * 60 * 24 * 365)

    subject = cert.get_subject()
    subject.CN = cn
    subject.O = "Dummy Certificate"  # noqa: E741

    issuer = cert.get_issuer()
    issuer.CN = subject.CN
    issuer.O = subject.O  # noqa: E741

    pkey = crypto.PKey()
    pkey.generate_key(crypto.TYPE_RSA, 2048)
    cert.set_pubkey(pkey)
    cert.sign(pkey, "sha256")

    return cert, pkey


def make_ssl_devcert(base_path, host=None, cn=None):
    """Creates an SSL key for development.  This should be used instead of
    the ``'adhoc'`` key which generates a new cert on each server start.
    It accepts a path for where it should store the key and cert and
    either a host or CN.  If a host is given it will use the CN
    ``*.host/CN=host``.

    For more information see :func:`run_simple`.

    .. versionadded:: 0.9

    :param base_path: the path to the certificate and key.  The extension
                      ``.crt`` is added for the certificate, ``.key`` is
                      added for the key.
    :param host: the name of the host.  This can be used as an alternative
                 for the `cn`.
    :param cn: the `CN` to use.
    """
    from OpenSSL import crypto

    if host is not None:
        cn = "*.%s/CN=%s" % (host, host)
    cert, pkey = generate_adhoc_ssl_pair(cn=cn)

    cert_file = base_path + ".crt"
    pkey_file = base_path + ".key"

    with open(cert_file, "wb") as f:
        f.write(crypto.dump_certificate(crypto.FILETYPE_PEM, cert))
    with open(pkey_file, "wb") as f:
        f.write(crypto.dump_privatekey(crypto.FILETYPE_PEM, pkey))

    return cert_file, pkey_file


def generate_adhoc_ssl_context():
    """Generates an adhoc SSL context for the development server."""
    crypto = _get_openssl_crypto_module()
    import tempfile
    import atexit

    cert, pkey = generate_adhoc_ssl_pair()
    cert_handle, cert_file = tempfile.mkstemp()
    pkey_handle, pkey_file = tempfile.mkstemp()
    atexit.register(os.remove, pkey_file)
    atexit.register(os.remove, cert_file)

    os.write(cert_handle, crypto.dump_certificate(crypto.FILETYPE_PEM, cert))
    os.write(pkey_handle, crypto.dump_privatekey(crypto.FILETYPE_PEM, pkey))
    os.close(cert_handle)
    os.close(pkey_handle)
    ctx = load_ssl_context(cert_file, pkey_file)
    return ctx


def load_ssl_context(cert_file, pkey_file=None, protocol=None):
    """Loads SSL context from cert/private key files and optional protocol.
    Many parameters are directly taken from the API of
    :py:class:`ssl.SSLContext`.

    :param cert_file: Path of the certificate to use.
    :param pkey_file: Path of the private key to use. If not given, the key
                      will be obtained from the certificate file.
    :param protocol: One of the ``PROTOCOL_*`` constants in the stdlib ``ssl``
                     module. Defaults to ``PROTOCOL_SSLv23``.
    """
    if protocol is None:
        protocol = ssl.PROTOCOL_SSLv23
    ctx = _SSLContext(protocol)
    ctx.load_cert_chain(cert_file, pkey_file)
    return ctx


class _SSLContext(object):

    """A dummy class with a small subset of Python3's ``ssl.SSLContext``, only
    intended to be used with and by Werkzeug."""

    def __init__(self, protocol):
        self._protocol = protocol
        self._certfile = None
        self._keyfile = None
        self._password = None

    def load_cert_chain(self, certfile, keyfile=None, password=None):
        self._certfile = certfile
        self._keyfile = keyfile or certfile
        self._password = password

    def wrap_socket(self, sock, **kwargs):
        return ssl.wrap_socket(
            sock,
            keyfile=self._keyfile,
            certfile=self._certfile,
            ssl_version=self._protocol,
            **kwargs
        )


def is_ssl_error(error=None):
    """Checks if the given error (or the current one) is an SSL error."""
    exc_types = (ssl.SSLError,)
    try:
        from OpenSSL.SSL import Error

        exc_types += (Error,)
    except ImportError:
        pass

    if error is None:
        error = sys.exc_info()[1]
    return isinstance(error, exc_types)


def select_address_family(host, port):
    """Return ``AF_INET4``, ``AF_INET6``, or ``AF_UNIX`` depending on
    the host and port."""
    # disabled due to problems with current ipv6 implementations
    # and various operating systems.  Probably this code also is
    # not supposed to work, but I can't come up with any other
    # ways to implement this.
    # try:
    #     info = socket.getaddrinfo(host, port, socket.AF_UNSPEC,
    #                               socket.SOCK_STREAM, 0,
    #                               socket.AI_PASSIVE)
    #     if info:
    #         return info[0][0]
    # except socket.gaierror:
    #     pass
    if host.startswith("unix://"):
        return socket.AF_UNIX
    elif ":" in host and hasattr(socket, "AF_INET6"):
        return socket.AF_INET6
    return socket.AF_INET


def get_sockaddr(host, port, family):
    """Return a fully qualified socket address that can be passed to
    :func:`socket.bind`."""
    if family == af_unix:
        return host.split("://", 1)[1]
    try:
        res = socket.getaddrinfo(
            host, port, family, socket.SOCK_STREAM, socket.IPPROTO_TCP
        )
    except socket.gaierror:
        return host, port
    return res[0][4]


class BaseWSGIServer(HTTPServer, object):

    """Simple single-threaded, single-process WSGI server."""

    multithread = False
    multiprocess = False
    request_queue_size = LISTEN_QUEUE

    def __init__(
        self,
        host,
        port,
        app,
        handler=None,
        passthrough_errors=False,
        ssl_context=None,
        fd=None,
    ):
        if handler is None:
            handler = WSGIRequestHandler

        self.address_family = select_address_family(host, port)

        if fd is not None:
            real_sock = socket.fromfd(fd, self.address_family, socket.SOCK_STREAM)
            port = 0

        server_address = get_sockaddr(host, int(port), self.address_family)

        # remove socket file if it already exists
        if self.address_family == af_unix and os.path.exists(server_address):
            os.unlink(server_address)
        HTTPServer.__init__(self, server_address, handler)

        self.app = app
        self.passthrough_errors = passthrough_errors
        self.shutdown_signal = False
        self.host = host
        self.port = self.socket.getsockname()[1]

        # Patch in the original socket.
        if fd is not None:
            self.socket.close()
            self.socket = real_sock
            self.server_address = self.socket.getsockname()

        if ssl_context is not None:
            if isinstance(ssl_context, tuple):
                ssl_context = load_ssl_context(*ssl_context)
            if ssl_context == "adhoc":
                ssl_context = generate_adhoc_ssl_context()
            # If we are on Python 2 the return value from socket.fromfd
            # is an internal socket object but what we need for ssl wrap
            # is the wrapper around it :(
            sock = self.socket
            if PY2 and not isinstance(sock, socket.socket):
                sock = socket.socket(sock.family, sock.type, sock.proto, sock)
            self.socket = ssl_context.wrap_socket(sock, server_side=True)
            self.ssl_context = ssl_context
        else:
            self.ssl_context = None

    def log(self, type, message, *args):
        _log(type, message, *args)

    def serve_forever(self):
        self.shutdown_signal = False
        try:
            HTTPServer.serve_forever(self)
        except KeyboardInterrupt:
            pass
        finally:
            self.server_close()

    def handle_error(self, request, client_address):
        if self.passthrough_errors:
            raise
        # Python 2 still causes a socket.error after the earlier
        # handling, so silence it here.
        if isinstance(sys.exc_info()[1], _ConnectionError):
            return
        return HTTPServer.handle_error(self, request, client_address)

    def get_request(self):
        con, info = self.socket.accept()
        return con, info


class ThreadedWSGIServer(ThreadingMixIn, BaseWSGIServer):

    """A WSGI server that does threading."""

    multithread = True
    daemon_threads = True


class ForkingWSGIServer(ForkingMixIn, BaseWSGIServer):

    """A WSGI server that does forking."""

    multiprocess = True

    def __init__(
        self,
        host,
        port,
        app,
        processes=40,
        handler=None,
        passthrough_errors=False,
        ssl_context=None,
        fd=None,
    ):
        if not can_fork:
            raise ValueError("Your platform does not support forking.")
        BaseWSGIServer.__init__(
            self, host, port, app, handler, passthrough_errors, ssl_context, fd
        )
        self.max_children = processes


def make_server(
    host=None,
    port=None,
    app=None,
    threaded=False,
    processes=1,
    request_handler=None,
    passthrough_errors=False,
    ssl_context=None,
    fd=None,
):
    """Create a new server instance that is either threaded, or forks
    or just processes one request after another.
    """
    if threaded and processes > 1:
        raise ValueError("cannot have a multithreaded and multi process server.")
    elif threaded:
        return ThreadedWSGIServer(
            host, port, app, request_handler, passthrough_errors, ssl_context, fd=fd
        )
    elif processes > 1:
        return ForkingWSGIServer(
            host,
            port,
            app,
            processes,
            request_handler,
            passthrough_errors,
            ssl_context,
            fd=fd,
        )
    else:
        return BaseWSGIServer(
            host, port, app, request_handler, passthrough_errors, ssl_context, fd=fd
        )


def is_running_from_reloader():
    """Checks if the application is running from within the Werkzeug
    reloader subprocess.

    .. versionadded:: 0.10
    """
    return os.environ.get("WERKZEUG_RUN_MAIN") == "true"


def run_simple(
    hostname,
    port,
    application,
    use_reloader=False,
    use_debugger=False,
    use_evalex=True,
    extra_files=None,
    reloader_interval=1,
    reloader_type="auto",
    threaded=False,
    processes=1,
    request_handler=None,
    static_files=None,
    passthrough_errors=False,
    ssl_context=None,
):
    """Start a WSGI application. Optional features include a reloader,
    multithreading and fork support.

    This function has a command-line interface too::

        python -m werkzeug.serving --help

    .. versionadded:: 0.5
       `static_files` was added to simplify serving of static files as well
       as `passthrough_errors`.

    .. versionadded:: 0.6
       support for SSL was added.

    .. versionadded:: 0.8
       Added support for automatically loading a SSL context from certificate
       file and private key.

    .. versionadded:: 0.9
       Added command-line interface.

    .. versionadded:: 0.10
       Improved the reloader and added support for changing the backend
       through the `reloader_type` parameter.  See :ref:`reloader`
       for more information.

    .. versionchanged:: 0.15
        Bind to a Unix socket by passing a path that starts with
        ``unix://`` as the ``hostname``.

    :param hostname: The host to bind to, for example ``'localhost'``.
        If the value is a path that starts with ``unix://`` it will bind
        to a Unix socket instead of a TCP socket..
    :param port: The port for the server.  eg: ``8080``
    :param application: the WSGI application to execute
    :param use_reloader: should the server automatically restart the python
                         process if modules were changed?
    :param use_debugger: should the werkzeug debugging system be used?
    :param use_evalex: should the exception evaluation feature be enabled?
    :param extra_files: a list of files the reloader should watch
                        additionally to the modules.  For example configuration
                        files.
    :param reloader_interval: the interval for the reloader in seconds.
    :param reloader_type: the type of reloader to use.  The default is
                          auto detection.  Valid values are ``'stat'`` and
                          ``'watchdog'``. See :ref:`reloader` for more
                          information.
    :param threaded: should the process handle each request in a separate
                     thread?
    :param processes: if greater than 1 then handle each request in a new process
                      up to this maximum number of concurrent processes.
    :param request_handler: optional parameter that can be used to replace
                            the default one.  You can use this to replace it
                            with a different
                            :class:`~BaseHTTPServer.BaseHTTPRequestHandler`
                            subclass.
    :param static_files: a list or dict of paths for static files.  This works
                         exactly like :class:`SharedDataMiddleware`, it's actually
                         just wrapping the application in that middleware before
                         serving.
    :param passthrough_errors: set this to `True` to disable the error catching.
                               This means that the server will die on errors but
                               it can be useful to hook debuggers in (pdb etc.)
    :param ssl_context: an SSL context for the connection. Either an
                        :class:`ssl.SSLContext`, a tuple in the form
                        ``(cert_file, pkey_file)``, the string ``'adhoc'`` if
                        the server should automatically create one, or ``None``
                        to disable SSL (which is the default).
    """
    if not isinstance(port, int):
        raise TypeError("port must be an integer")
    if use_debugger:
        from .debug import DebuggedApplication

        application = DebuggedApplication(application, use_evalex)
    if static_files:
        from .middleware.shared_data import SharedDataMiddleware

        application = SharedDataMiddleware(application, static_files)

    def log_startup(sock):
        display_hostname = hostname if hostname not in ("", "*") else "localhost"
        quit_msg = "(Press CTRL+C to quit)"
        if sock.family == af_unix:
            _log("info", " * Running on %s %s", display_hostname, quit_msg)
        else:
            if ":" in display_hostname:
                display_hostname = "[%s]" % display_hostname
            port = sock.getsockname()[1]
            _log(
                "info",
                " * Running on %s://%s:%d/ %s",
                "http" if ssl_context is None else "https",
                display_hostname,
                port,
                quit_msg,
            )

    def inner():
        try:
            fd = int(os.environ["WERKZEUG_SERVER_FD"])
        except (LookupError, ValueError):
            fd = None
        srv = make_server(
            hostname,
            port,
            application,
            threaded,
            processes,
            request_handler,
            passthrough_errors,
            ssl_context,
            fd=fd,
        )
        if fd is None:
            log_startup(srv.socket)
        srv.serve_forever()

    if use_reloader:
        # If we're not running already in the subprocess that is the
        # reloader we want to open up a socket early to make sure the
        # port is actually available.
        if not is_running_from_reloader():
            if port == 0 and not can_open_by_fd:
                raise ValueError(
                    "Cannot bind to a random port with enabled "
                    "reloader if the Python interpreter does "
                    "not support socket opening by fd."
                )

            # Create and destroy a socket so that any exceptions are
            # raised before we spawn a separate Python interpreter and
            # lose this ability.
            address_family = select_address_family(hostname, port)
            server_address = get_sockaddr(hostname, port, address_family)
            s = socket.socket(address_family, socket.SOCK_STREAM)
            s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
            s.bind(server_address)
            if hasattr(s, "set_inheritable"):
                s.set_inheritable(True)

            # If we can open the socket by file descriptor, then we can just
            # reuse this one and our socket will survive the restarts.
            if can_open_by_fd:
                os.environ["WERKZEUG_SERVER_FD"] = str(s.fileno())
                s.listen(LISTEN_QUEUE)
                log_startup(s)
            else:
                s.close()
                if address_family == af_unix:
                    _log("info", "Unlinking %s" % server_address)
                    os.unlink(server_address)

        # Do not use relative imports, otherwise "python -m werkzeug.serving"
        # breaks.
        from ._reloader import run_with_reloader

        run_with_reloader(inner, extra_files, reloader_interval, reloader_type)
    else:
        inner()


def run_with_reloader(*args, **kwargs):
    # People keep using undocumented APIs.  Do not use this function
    # please, we do not guarantee that it continues working.
    from ._reloader import run_with_reloader

    return run_with_reloader(*args, **kwargs)


def main():
    """A simple command-line interface for :py:func:`run_simple`."""

    # in contrast to argparse, this works at least under Python < 2.7
    import optparse
    from .utils import import_string

    parser = optparse.OptionParser(usage="Usage: %prog [options] app_module:app_object")
    parser.add_option(
        "-b",
        "--bind",
        dest="address",
        help="The hostname:port the app should listen on.",
    )
    parser.add_option(
        "-d",
        "--debug",
        dest="use_debugger",
        action="store_true",
        default=False,
        help="Use Werkzeug's debugger.",
    )
    parser.add_option(
        "-r",
        "--reload",
        dest="use_reloader",
        action="store_true",
        default=False,
        help="Reload Python process if modules change.",
    )
    options, args = parser.parse_args()

    hostname, port = None, None
    if options.address:
        address = options.address.split(":")
        hostname = address[0]
        if len(address) > 1:
            port = address[1]

    if len(args) != 1:
        sys.stdout.write("No application supplied, or too much. See --help\n")
        sys.exit(1)
    app = import_string(args[0])

    run_simple(
        hostname=(hostname or "127.0.0.1"),
        port=int(port or 5000),
        application=app,
        use_reloader=options.use_reloader,
        use_debugger=options.use_debugger,
    )


if __name__ == "__main__":
    main()