/Lib/test/test_socket.py

Large files files are truncated, but you can click here to view the full file

#!/usr/bin/env python3

import unittest
from test import support
from unittest.case import _ExpectedFailure

import errno
import io
import socket
import select
import tempfile
import _testcapi
import time
import traceback
import queue
import sys
import os
import array
import platform
import contextlib
from weakref import proxy
import signal
import math
import pickle
import struct
try:
    import fcntl
except ImportError:
    fcntl = False
try:
    import multiprocessing
except ImportError:
    multiprocessing = False

HOST = support.HOST
MSG = 'Michael Gilfix was here\u1234\r\n'.encode('utf-8') ## test unicode string and carriage return

try:
    import _thread as thread
    import threading
except ImportError:
    thread = None
    threading = None

def _have_socket_can():
    """Check whether CAN sockets are supported on this host."""
    try:
        s = socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
    except (AttributeError, OSError):
        return False
    else:
        s.close()
    return True

def _have_socket_rds():
    """Check whether RDS sockets are supported on this host."""
    try:
        s = socket.socket(socket.PF_RDS, socket.SOCK_SEQPACKET, 0)
    except (AttributeError, OSError):
        return False
    else:
        s.close()
    return True

HAVE_SOCKET_CAN = _have_socket_can()

HAVE_SOCKET_RDS = _have_socket_rds()

# Size in bytes of the int type
SIZEOF_INT = array.array("i").itemsize

class SocketTCPTest(unittest.TestCase):

    def setUp(self):
        self.serv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.port = support.bind_port(self.serv)
        self.serv.listen(1)

    def tearDown(self):
        self.serv.close()
        self.serv = None

class SocketUDPTest(unittest.TestCase):

    def setUp(self):
        self.serv = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.port = support.bind_port(self.serv)

    def tearDown(self):
        self.serv.close()
        self.serv = None

class ThreadSafeCleanupTestCase(unittest.TestCase):
    """Subclass of unittest.TestCase with thread-safe cleanup methods.

    This subclass protects the addCleanup() and doCleanups() methods
    with a recursive lock.
    """

    if threading:
        def __init__(self, *args, **kwargs):
            super().__init__(*args, **kwargs)
            self._cleanup_lock = threading.RLock()

        def addCleanup(self, *args, **kwargs):
            with self._cleanup_lock:
                return super().addCleanup(*args, **kwargs)

        def doCleanups(self, *args, **kwargs):
            with self._cleanup_lock:
                return super().doCleanups(*args, **kwargs)

class SocketCANTest(unittest.TestCase):

    """To be able to run this test, a `vcan0` CAN interface can be created with
    the following commands:
    # modprobe vcan
    # ip link add dev vcan0 type vcan
    # ifconfig vcan0 up
    """
    interface = 'vcan0'
    bufsize = 128

    def setUp(self):
        self.s = socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
        self.addCleanup(self.s.close)
        try:
            self.s.bind((self.interface,))
        except OSError:
            self.skipTest('network interface `%s` does not exist' %
                           self.interface)


class SocketRDSTest(unittest.TestCase):

    """To be able to run this test, the `rds` kernel module must be loaded:
    # modprobe rds
    """
    bufsize = 8192

    def setUp(self):
        self.serv = socket.socket(socket.PF_RDS, socket.SOCK_SEQPACKET, 0)
        self.addCleanup(self.serv.close)
        try:
            self.port = support.bind_port(self.serv)
        except OSError:
            self.skipTest('unable to bind RDS socket')


class ThreadableTest:
    """Threadable Test class

    The ThreadableTest class makes it easy to create a threaded
    client/server pair from an existing unit test. To create a
    new threaded class from an existing unit test, use multiple
    inheritance:

        class NewClass (OldClass, ThreadableTest):
            pass

    This class defines two new fixture functions with obvious
    purposes for overriding:

        clientSetUp ()
        clientTearDown ()

    Any new test functions within the class must then define
    tests in pairs, where the test name is preceeded with a
    '_' to indicate the client portion of the test. Ex:

        def testFoo(self):
            # Server portion

        def _testFoo(self):
            # Client portion

    Any exceptions raised by the clients during their tests
    are caught and transferred to the main thread to alert
    the testing framework.

    Note, the server setup function cannot call any blocking
    functions that rely on the client thread during setup,
    unless serverExplicitReady() is called just before
    the blocking call (such as in setting up a client/server
    connection and performing the accept() in setUp().
    """

    def __init__(self):
        # Swap the true setup function
        self.__setUp = self.setUp
        self.__tearDown = self.tearDown
        self.setUp = self._setUp
        self.tearDown = self._tearDown

    def serverExplicitReady(self):
        """This method allows the server to explicitly indicate that
        it wants the client thread to proceed. This is useful if the
        server is about to execute a blocking routine that is
        dependent upon the client thread during its setup routine."""
        self.server_ready.set()

    def _setUp(self):
        self.server_ready = threading.Event()
        self.client_ready = threading.Event()
        self.done = threading.Event()
        self.queue = queue.Queue(1)
        self.server_crashed = False

        # Do some munging to start the client test.
        methodname = self.id()
        i = methodname.rfind('.')
        methodname = methodname[i+1:]
        test_method = getattr(self, '_' + methodname)
        self.client_thread = thread.start_new_thread(
            self.clientRun, (test_method,))

        try:
            self.__setUp()
        except:
            self.server_crashed = True
            raise
        finally:
            self.server_ready.set()
        self.client_ready.wait()

    def _tearDown(self):
        self.__tearDown()
        self.done.wait()

        if self.queue.qsize():
            exc = self.queue.get()
            raise exc

    def clientRun(self, test_func):
        self.server_ready.wait()
        self.clientSetUp()
        self.client_ready.set()
        if self.server_crashed:
            self.clientTearDown()
            return
        if not hasattr(test_func, '__call__'):
            raise TypeError("test_func must be a callable function")
        try:
            test_func()
        except _ExpectedFailure:
            # We deliberately ignore expected failures
            pass
        except BaseException as e:
            self.queue.put(e)
        finally:
            self.clientTearDown()

    def clientSetUp(self):
        raise NotImplementedError("clientSetUp must be implemented.")

    def clientTearDown(self):
        self.done.set()
        thread.exit()

class ThreadedTCPSocketTest(SocketTCPTest, ThreadableTest):

    def __init__(self, methodName='runTest'):
        SocketTCPTest.__init__(self, methodName=methodName)
        ThreadableTest.__init__(self)

    def clientSetUp(self):
        self.cli = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    def clientTearDown(self):
        self.cli.close()
        self.cli = None
        ThreadableTest.clientTearDown(self)

class ThreadedUDPSocketTest(SocketUDPTest, ThreadableTest):

    def __init__(self, methodName='runTest'):
        SocketUDPTest.__init__(self, methodName=methodName)
        ThreadableTest.__init__(self)

    def clientSetUp(self):
        self.cli = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

    def clientTearDown(self):
        self.cli.close()
        self.cli = None
        ThreadableTest.clientTearDown(self)

class ThreadedCANSocketTest(SocketCANTest, ThreadableTest):

    def __init__(self, methodName='runTest'):
        SocketCANTest.__init__(self, methodName=methodName)
        ThreadableTest.__init__(self)

    def clientSetUp(self):
        self.cli = socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW)
        try:
            self.cli.bind((self.interface,))
        except OSError:
            # skipTest should not be called here, and will be called in the
            # server instead
            pass

    def clientTearDown(self):
        self.cli.close()
        self.cli = None
        ThreadableTest.clientTearDown(self)

class ThreadedRDSSocketTest(SocketRDSTest, ThreadableTest):

    def __init__(self, methodName='runTest'):
        SocketRDSTest.__init__(self, methodName=methodName)
        ThreadableTest.__init__(self)

    def clientSetUp(self):
        self.cli = socket.socket(socket.PF_RDS, socket.SOCK_SEQPACKET, 0)
        try:
            # RDS sockets must be bound explicitly to send or receive data
            self.cli.bind((HOST, 0))
            self.cli_addr = self.cli.getsockname()
        except OSError:
            # skipTest should not be called here, and will be called in the
            # server instead
            pass

    def clientTearDown(self):
        self.cli.close()
        self.cli = None
        ThreadableTest.clientTearDown(self)

class SocketConnectedTest(ThreadedTCPSocketTest):
    """Socket tests for client-server connection.

    self.cli_conn is a client socket connected to the server.  The
    setUp() method guarantees that it is connected to the server.
    """

    def __init__(self, methodName='runTest'):
        ThreadedTCPSocketTest.__init__(self, methodName=methodName)

    def setUp(self):
        ThreadedTCPSocketTest.setUp(self)
        # Indicate explicitly we're ready for the client thread to
        # proceed and then perform the blocking call to accept
        self.serverExplicitReady()
        conn, addr = self.serv.accept()
        self.cli_conn = conn

    def tearDown(self):
        self.cli_conn.close()
        self.cli_conn = None
        ThreadedTCPSocketTest.tearDown(self)

    def clientSetUp(self):
        ThreadedTCPSocketTest.clientSetUp(self)
        self.cli.connect((HOST, self.port))
        self.serv_conn = self.cli

    def clientTearDown(self):
        self.serv_conn.close()
        self.serv_conn = None
        ThreadedTCPSocketTest.clientTearDown(self)

class SocketPairTest(unittest.TestCase, ThreadableTest):

    def __init__(self, methodName='runTest'):
        unittest.TestCase.__init__(self, methodName=methodName)
        ThreadableTest.__init__(self)

    def setUp(self):
        self.serv, self.cli = socket.socketpair()

    def tearDown(self):
        self.serv.close()
        self.serv = None

    def clientSetUp(self):
        pass

    def clientTearDown(self):
        self.cli.close()
        self.cli = None
        ThreadableTest.clientTearDown(self)


# The following classes are used by the sendmsg()/recvmsg() tests.
# Combining, for instance, ConnectedStreamTestMixin and TCPTestBase
# gives a drop-in replacement for SocketConnectedTest, but different
# address families can be used, and the attributes serv_addr and
# cli_addr will be set to the addresses of the endpoints.

class SocketTestBase(unittest.TestCase):
    """A base class for socket tests.

    Subclasses must provide methods newSocket() to return a new socket
    and bindSock(sock) to bind it to an unused address.

    Creates a socket self.serv and sets self.serv_addr to its address.
    """

    def setUp(self):
        self.serv = self.newSocket()
        self.bindServer()

    def bindServer(self):
        """Bind server socket and set self.serv_addr to its address."""
        self.bindSock(self.serv)
        self.serv_addr = self.serv.getsockname()

    def tearDown(self):
        self.serv.close()
        self.serv = None


class SocketListeningTestMixin(SocketTestBase):
    """Mixin to listen on the server socket."""

    def setUp(self):
        super().setUp()
        self.serv.listen(1)


class ThreadedSocketTestMixin(ThreadSafeCleanupTestCase, SocketTestBase,
                              ThreadableTest):
    """Mixin to add client socket and allow client/server tests.

    Client socket is self.cli and its address is self.cli_addr.  See
    ThreadableTest for usage information.
    """

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        ThreadableTest.__init__(self)

    def clientSetUp(self):
        self.cli = self.newClientSocket()
        self.bindClient()

    def newClientSocket(self):
        """Return a new socket for use as client."""
        return self.newSocket()

    def bindClient(self):
        """Bind client socket and set self.cli_addr to its address."""
        self.bindSock(self.cli)
        self.cli_addr = self.cli.getsockname()

    def clientTearDown(self):
        self.cli.close()
        self.cli = None
        ThreadableTest.clientTearDown(self)


class ConnectedStreamTestMixin(SocketListeningTestMixin,
                               ThreadedSocketTestMixin):
    """Mixin to allow client/server stream tests with connected client.

    Server's socket representing connection to client is self.cli_conn
    and client's connection to server is self.serv_conn.  (Based on
    SocketConnectedTest.)
    """

    def setUp(self):
        super().setUp()
        # Indicate explicitly we're ready for the client thread to
        # proceed and then perform the blocking call to accept
        self.serverExplicitReady()
        conn, addr = self.serv.accept()
        self.cli_conn = conn

    def tearDown(self):
        self.cli_conn.close()
        self.cli_conn = None
        super().tearDown()

    def clientSetUp(self):
        super().clientSetUp()
        self.cli.connect(self.serv_addr)
        self.serv_conn = self.cli

    def clientTearDown(self):
        self.serv_conn.close()
        self.serv_conn = None
        super().clientTearDown()


class UnixSocketTestBase(SocketTestBase):
    """Base class for Unix-domain socket tests."""

    # This class is used for file descriptor passing tests, so we
    # create the sockets in a private directory so that other users
    # can't send anything that might be problematic for a privileged
    # user running the tests.

    def setUp(self):
        self.dir_path = tempfile.mkdtemp()
        self.addCleanup(os.rmdir, self.dir_path)
        super().setUp()

    def bindSock(self, sock):
        path = tempfile.mktemp(dir=self.dir_path)
        sock.bind(path)
        self.addCleanup(support.unlink, path)

class UnixStreamBase(UnixSocketTestBase):
    """Base class for Unix-domain SOCK_STREAM tests."""

    def newSocket(self):
        return socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)


class InetTestBase(SocketTestBase):
    """Base class for IPv4 socket tests."""

    host = HOST

    def setUp(self):
        super().setUp()
        self.port = self.serv_addr[1]

    def bindSock(self, sock):
        support.bind_port(sock, host=self.host)

class TCPTestBase(InetTestBase):
    """Base class for TCP-over-IPv4 tests."""

    def newSocket(self):
        return socket.socket(socket.AF_INET, socket.SOCK_STREAM)

class UDPTestBase(InetTestBase):
    """Base class for UDP-over-IPv4 tests."""

    def newSocket(self):
        return socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

class SCTPStreamBase(InetTestBase):
    """Base class for SCTP tests in one-to-one (SOCK_STREAM) mode."""

    def newSocket(self):
        return socket.socket(socket.AF_INET, socket.SOCK_STREAM,
                             socket.IPPROTO_SCTP)


class Inet6TestBase(InetTestBase):
    """Base class for IPv6 socket tests."""

    # Don't use "localhost" here - it may not have an IPv6 address
    # assigned to it by default (e.g. in /etc/hosts), and if someone
    # has assigned it an IPv4-mapped address, then it's unlikely to
    # work with the full IPv6 API.
    host = "::1"

class UDP6TestBase(Inet6TestBase):
    """Base class for UDP-over-IPv6 tests."""

    def newSocket(self):
        return socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)


# Test-skipping decorators for use with ThreadableTest.

def skipWithClientIf(condition, reason):
    """Skip decorated test if condition is true, add client_skip decorator.

    If the decorated object is not a class, sets its attribute
    "client_skip" to a decorator which will return an empty function
    if the test is to be skipped, or the original function if it is
    not.  This can be used to avoid running the client part of a
    skipped test when using ThreadableTest.
    """
    def client_pass(*args, **kwargs):
        pass
    def skipdec(obj):
        retval = unittest.skip(reason)(obj)
        if not isinstance(obj, type):
            retval.client_skip = lambda f: client_pass
        return retval
    def noskipdec(obj):
        if not (isinstance(obj, type) or hasattr(obj, "client_skip")):
            obj.client_skip = lambda f: f
        return obj
    return skipdec if condition else noskipdec


def requireAttrs(obj, *attributes):
    """Skip decorated test if obj is missing any of the given attributes.

    Sets client_skip attribute as skipWithClientIf() does.
    """
    missing = [name for name in attributes if not hasattr(obj, name)]
    return skipWithClientIf(
        missing, "don't have " + ", ".join(name for name in missing))


def requireSocket(*args):
    """Skip decorated test if a socket cannot be created with given arguments.

    When an argument is given as a string, will use the value of that
    attribute of the socket module, or skip the test if it doesn't
    exist.  Sets client_skip attribute as skipWithClientIf() does.
    """
    err = None
    missing = [obj for obj in args if
               isinstance(obj, str) and not hasattr(socket, obj)]
    if missing:
        err = "don't have " + ", ".join(name for name in missing)
    else:
        callargs = [getattr(socket, obj) if isinstance(obj, str) else obj
                    for obj in args]
        try:
            s = socket.socket(*callargs)
        except OSError as e:
            # XXX: check errno?
            err = str(e)
        else:
            s.close()
    return skipWithClientIf(
        err is not None,
        "can't create socket({0}): {1}".format(
            ", ".join(str(o) for o in args), err))


#######################################################################
## Begin Tests

class GeneralModuleTests(unittest.TestCase):

    def test_repr(self):
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.addCleanup(s.close)
        self.assertTrue(repr(s).startswith("<socket.socket object"))

    def test_weakref(self):
        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        p = proxy(s)
        self.assertEqual(p.fileno(), s.fileno())
        s.close()
        s = None
        try:
            p.fileno()
        except ReferenceError:
            pass
        else:
            self.fail('Socket proxy still exists')

    def testSocketError(self):
        # Testing socket module exceptions
        msg = "Error raising socket exception (%s)."
        with self.assertRaises(OSError, msg=msg % 'OSError'):
            raise OSError
        with self.assertRaises(OSError, msg=msg % 'socket.herror'):
            raise socket.herror
        with self.assertRaises(OSError, msg=msg % 'socket.gaierror'):
            raise socket.gaierror

    def testSendtoErrors(self):
        # Testing that sendto doens't masks failures. See #10169.
        s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
        self.addCleanup(s.close)
        s.bind(('', 0))
        sockname = s.getsockname()
        # 2 args
        with self.assertRaises(TypeError) as cm:
            s.sendto('\u2620', sockname)
        self.assertEqual(str(cm.exception),
                         "'str' does not support the buffer interface")
        with self.assertRaises(TypeError) as cm:
            s.sendto(5j, sockname)
        self.assertEqual(str(cm.exception),
                         "'complex' does not support the buffer interface")
        with self.assertRaises(TypeError) as cm:
            s.sendto(b'foo', None)
        self.assertIn('not NoneType',str(cm.exception))
        # 3 args
        with self.assertRaises(TypeError) as cm:
            s.sendto('\u2620', 0, sockname)
        self.assertEqual(str(cm.exception),
                         "'str' does not support the buffer interface")
        with self.assertRaises(TypeError) as cm:
            s.sendto(5j, 0, sockname)
        self.assertEqual(str(cm.exception),
                         "'complex' does not support the buffer interface")
        with self.assertRaises(TypeError) as cm:
            s.sendto(b'foo', 0, None)
        self.assertIn('not NoneType', str(cm.exception))
        with self.assertRaises(TypeError) as cm:
            s.sendto(b'foo', 'bar', sockname)
        self.assertIn('an integer is required', str(cm.exception))
        with self.assertRaises(TypeError) as cm:
            s.sendto(b'foo', None, None)
        self.assertIn('an integer is required', str(cm.exception))
        # wrong number of args
        with self.assertRaises(TypeError) as cm:
            s.sendto(b'foo')
        self.assertIn('(1 given)', str(cm.exception))
        with self.assertRaises(TypeError) as cm:
            s.sendto(b'foo', 0, sockname, 4)
        self.assertIn('(4 given)', str(cm.exception))

    def testCrucialConstants(self):
        # Testing for mission critical constants
        socket.AF_INET
        socket.SOCK_STREAM
        socket.SOCK_DGRAM
        socket.SOCK_RAW
        socket.SOCK_RDM
        socket.SOCK_SEQPACKET
        socket.SOL_SOCKET
        socket.SO_REUSEADDR

    def testHostnameRes(self):
        # Testing hostname resolution mechanisms
        hostname = socket.gethostname()
        try:
            ip = socket.gethostbyname(hostname)
        except OSError:
            # Probably name lookup wasn't set up right; skip this test
            return
        self.assertTrue(ip.find('.') >= 0, "Error resolving host to ip.")
        try:
            hname, aliases, ipaddrs = socket.gethostbyaddr(ip)
        except OSError:
            # Probably a similar problem as above; skip this test
            return
        all_host_names = [hostname, hname] + aliases
        fqhn = socket.getfqdn(ip)
        if not fqhn in all_host_names:
            self.fail("Error testing host resolution mechanisms. (fqdn: %s, all: %s)" % (fqhn, repr(all_host_names)))

    @unittest.skipUnless(hasattr(socket, 'sethostname'), "test needs socket.sethostname()")
    @unittest.skipUnless(hasattr(socket, 'gethostname'), "test needs socket.gethostname()")
    def test_sethostname(self):
        oldhn = socket.gethostname()
        try:
            socket.sethostname('new')
        except OSError as e:
            if e.errno == errno.EPERM:
                self.skipTest("test should be run as root")
            else:
                raise
        try:
            # running test as root!
            self.assertEqual(socket.gethostname(), 'new')
            # Should work with bytes objects too
            socket.sethostname(b'bar')
            self.assertEqual(socket.gethostname(), 'bar')
        finally:
            socket.sethostname(oldhn)

    @unittest.skipUnless(hasattr(socket, 'if_nameindex'),
                         'socket.if_nameindex() not available.')
    def testInterfaceNameIndex(self):
        interfaces = socket.if_nameindex()
        for index, name in interfaces:
            self.assertIsInstance(index, int)
            self.assertIsInstance(name, str)
            # interface indices are non-zero integers
            self.assertGreater(index, 0)
            _index = socket.if_nametoindex(name)
            self.assertIsInstance(_index, int)
            self.assertEqual(index, _index)
            _name = socket.if_indextoname(index)
            self.assertIsInstance(_name, str)
            self.assertEqual(name, _name)

    @unittest.skipUnless(hasattr(socket, 'if_nameindex'),
                         'socket.if_nameindex() not available.')
    def testInvalidInterfaceNameIndex(self):
        # test nonexistent interface index/name
        self.assertRaises(OSError, socket.if_indextoname, 0)
        self.assertRaises(OSError, socket.if_nametoindex, '_DEADBEEF')
        # test with invalid values
        self.assertRaises(TypeError, socket.if_nametoindex, 0)
        self.assertRaises(TypeError, socket.if_indextoname, '_DEADBEEF')

    def testRefCountGetNameInfo(self):
        # Testing reference count for getnameinfo
        if hasattr(sys, "getrefcount"):
            try:
                # On some versions, this loses a reference
                orig = sys.getrefcount(__name__)
                socket.getnameinfo(__name__,0)
            except TypeError:
                if sys.getrefcount(__name__) != orig:
                    self.fail("socket.getnameinfo loses a reference")

    def testInterpreterCrash(self):
        # Making sure getnameinfo doesn't crash the interpreter
        try:
            # On some versions, this crashes the interpreter.
            socket.getnameinfo(('x', 0, 0, 0), 0)
        except OSError:
            pass

    def testNtoH(self):
        # This just checks that htons etc. are their own inverse,
        # when looking at the lower 16 or 32 bits.
        sizes = {socket.htonl: 32, socket.ntohl: 32,
                 socket.htons: 16, socket.ntohs: 16}
        for func, size in sizes.items():
            mask = (1<<size) - 1
            for i in (0, 1, 0xffff, ~0xffff, 2, 0x01234567, 0x76543210):
                self.assertEqual(i & mask, func(func(i&mask)) & mask)

            swapped = func(mask)
            self.assertEqual(swapped & mask, mask)
            self.assertRaises(OverflowError, func, 1<<34)

    def testNtoHErrors(self):
        good_values = [ 1, 2, 3, 1, 2, 3 ]
        bad_values = [ -1, -2, -3, -1, -2, -3 ]
        for k in good_values:
            socket.ntohl(k)
            socket.ntohs(k)
            socket.htonl(k)
            socket.htons(k)
        for k in bad_values:
            self.assertRaises(OverflowError, socket.ntohl, k)
            self.assertRaises(OverflowError, socket.ntohs, k)
            self.assertRaises(OverflowError, socket.htonl, k)
            self.assertRaises(OverflowError, socket.htons, k)

    def testGetServBy(self):
        eq = self.assertEqual
        # Find one service that exists, then check all the related interfaces.
        # I've ordered this by protocols that have both a tcp and udp
        # protocol, at least for modern Linuxes.
        if (sys.platform.startswith(('freebsd', 'netbsd'))
            or sys.platform in ('linux', 'darwin')):
            # avoid the 'echo' service on this platform, as there is an
            # assumption breaking non-standard port/protocol entry
            services = ('daytime', 'qotd', 'domain')
        else:
            services = ('echo', 'daytime', 'domain')
        for service in services:
            try:
                port = socket.getservbyname(service, 'tcp')
                break
            except OSError:
                pass
        else:
            raise OSError
        # Try same call with optional protocol omitted
        port2 = socket.getservbyname(service)
        eq(port, port2)
        # Try udp, but don't barf it it doesn't exist
        try:
            udpport = socket.getservbyname(service, 'udp')
        except OSError:
            udpport = None
        else:
            eq(udpport, port)
        # Now make sure the lookup by port returns the same service name
        eq(socket.getservbyport(port2), service)
        eq(socket.getservbyport(port, 'tcp'), service)
        if udpport is not None:
            eq(socket.getservbyport(udpport, 'udp'), service)
        # Make sure getservbyport does not accept out of range ports.
        self.assertRaises(OverflowError, socket.getservbyport, -1)
        self.assertRaises(OverflowError, socket.getservbyport, 65536)

    def testDefaultTimeout(self):
        # Testing default timeout
        # The default timeout should initially be None
        self.assertEqual(socket.getdefaulttimeout(), None)
        s = socket.socket()
        self.assertEqual(s.gettimeout(), None)
        s.close()

        # Set the default timeout to 10, and see if it propagates
        socket.setdefaulttimeout(10)
        self.assertEqual(socket.getdefaulttimeout(), 10)
        s = socket.socket()
        self.assertEqual(s.gettimeout(), 10)
        s.close()

        # Reset the default timeout to None, and see if it propagates
        socket.setdefaulttimeout(None)
        self.assertEqual(socket.getdefaulttimeout(), None)
        s = socket.socket()
        self.assertEqual(s.gettimeout(), None)
        s.close()

        # Check that setting it to an invalid value raises ValueError
        self.assertRaises(ValueError, socket.setdefaulttimeout, -1)

        # Check that setting it to an invalid type raises TypeError
        self.assertRaises(TypeError, socket.setdefaulttimeout, "spam")

    def testIPv4_inet_aton_fourbytes(self):
        if not hasattr(socket, 'inet_aton'):
            return  # No inet_aton, nothing to check
        # Test that issue1008086 and issue767150 are fixed.
        # It must return 4 bytes.
        self.assertEqual(b'\x00'*4, socket.inet_aton('0.0.0.0'))
        self.assertEqual(b'\xff'*4, socket.inet_aton('255.255.255.255'))

    def testIPv4toString(self):
        if not hasattr(socket, 'inet_pton'):
            return # No inet_pton() on this platform
        from socket import inet_aton as f, inet_pton, AF_INET
        g = lambda a: inet_pton(AF_INET, a)

        assertInvalid = lambda func,a: self.assertRaises(
            (OSError, ValueError), func, a
        )

        self.assertEqual(b'\x00\x00\x00\x00', f('0.0.0.0'))
        self.assertEqual(b'\xff\x00\xff\x00', f('255.0.255.0'))
        self.assertEqual(b'\xaa\xaa\xaa\xaa', f('170.170.170.170'))
        self.assertEqual(b'\x01\x02\x03\x04', f('1.2.3.4'))
        self.assertEqual(b'\xff\xff\xff\xff', f('255.255.255.255'))
        assertInvalid(f, '0.0.0.')
        assertInvalid(f, '300.0.0.0')
        assertInvalid(f, 'a.0.0.0')
        assertInvalid(f, '1.2.3.4.5')
        assertInvalid(f, '::1')

        self.assertEqual(b'\x00\x00\x00\x00', g('0.0.0.0'))
        self.assertEqual(b'\xff\x00\xff\x00', g('255.0.255.0'))
        self.assertEqual(b'\xaa\xaa\xaa\xaa', g('170.170.170.170'))
        self.assertEqual(b'\xff\xff\xff\xff', g('255.255.255.255'))
        assertInvalid(g, '0.0.0.')
        assertInvalid(g, '300.0.0.0')
        assertInvalid(g, 'a.0.0.0')
        assertInvalid(g, '1.2.3.4.5')
        assertInvalid(g, '::1')

    def testIPv6toString(self):
        if not hasattr(socket, 'inet_pton'):
            return # No inet_pton() on this platform
        try:
            from socket import inet_pton, AF_INET6, has_ipv6
            if not has_ipv6:
                return
        except ImportError:
            return
        f = lambda a: inet_pton(AF_INET6, a)
        assertInvalid = lambda a: self.assertRaises(
            (OSError, ValueError), f, a
        )

        self.assertEqual(b'\x00' * 16, f('::'))
        self.assertEqual(b'\x00' * 16, f('0::0'))
        self.assertEqual(b'\x00\x01' + b'\x00' * 14, f('1::'))
        self.assertEqual(
            b'\x45\xef\x76\xcb\x00\x1a\x56\xef\xaf\xeb\x0b\xac\x19\x24\xae\xae',
            f('45ef:76cb:1a:56ef:afeb:bac:1924:aeae')
        )
        self.assertEqual(
            b'\xad\x42\x0a\xbc' + b'\x00' * 4 + b'\x01\x27\x00\x00\x02\x54\x00\x02',
            f('ad42:abc::127:0:254:2')
        )
        self.assertEqual(b'\x00\x12\x00\x0a' + b'\x00' * 12, f('12:a::'))
        assertInvalid('0x20::')
        assertInvalid(':::')
        assertInvalid('::0::')
        assertInvalid('1::abc::')
        assertInvalid('1::abc::def')
        assertInvalid('1:2:3:4:5:6:')
        assertInvalid('1:2:3:4:5:6')
        assertInvalid('1:2:3:4:5:6:7:8:')
        assertInvalid('1:2:3:4:5:6:7:8:0')

        self.assertEqual(b'\x00' * 12 + b'\xfe\x2a\x17\x40',
            f('::254.42.23.64')
        )
        self.assertEqual(
            b'\x00\x42' + b'\x00' * 8 + b'\xa2\x9b\xfe\x2a\x17\x40',
            f('42::a29b:254.42.23.64')
        )
        self.assertEqual(
            b'\x00\x42\xa8\xb9\x00\x00\x00\x02\xff\xff\xa2\x9b\xfe\x2a\x17\x40',
            f('42:a8b9:0:2:ffff:a29b:254.42.23.64')
        )
        assertInvalid('255.254.253.252')
        assertInvalid('1::260.2.3.0')
        assertInvalid('1::0.be.e.0')
        assertInvalid('1:2:3:4:5:6:7:1.2.3.4')
        assertInvalid('::1.2.3.4:0')
        assertInvalid('0.100.200.0:3:4:5:6:7:8')

    def testStringToIPv4(self):
        if not hasattr(socket, 'inet_ntop'):
            return # No inet_ntop() on this platform
        from socket import inet_ntoa as f, inet_ntop, AF_INET
        g = lambda a: inet_ntop(AF_INET, a)
        assertInvalid = lambda func,a: self.assertRaises(
            (OSError, ValueError), func, a
        )

        self.assertEqual('1.0.1.0', f(b'\x01\x00\x01\x00'))
        self.assertEqual('170.85.170.85', f(b'\xaa\x55\xaa\x55'))
        self.assertEqual('255.255.255.255', f(b'\xff\xff\xff\xff'))
        self.assertEqual('1.2.3.4', f(b'\x01\x02\x03\x04'))
        assertInvalid(f, b'\x00' * 3)
        assertInvalid(f, b'\x00' * 5)
        assertInvalid(f, b'\x00' * 16)

        self.assertEqual('1.0.1.0', g(b'\x01\x00\x01\x00'))
        self.assertEqual('170.85.170.85', g(b'\xaa\x55\xaa\x55'))
        self.assertEqual('255.255.255.255', g(b'\xff\xff\xff\xff'))
        assertInvalid(g, b'\x00' * 3)
        assertInvalid(g, b'\x00' * 5)
        assertInvalid(g, b'\x00' * 16)

    def testStringToIPv6(self):
        if not hasattr(socket, 'inet_ntop'):
            return # No inet_ntop() on this platform
        try:
            from socket import inet_ntop, AF_INET6, has_ipv6
            if not has_ipv6:
                return
        except ImportError:
            return
        f = lambda a: inet_ntop(AF_INET6, a)
        assertInvalid = lambda a: self.assertRaises(
            (OSError, ValueError), f, a
        )

        self.assertEqual('::', f(b'\x00' * 16))
        self.assertEqual('::1', f(b'\x00' * 15 + b'\x01'))
        self.assertEqual(
            'aef:b01:506:1001:ffff:9997:55:170',
            f(b'\x0a\xef\x0b\x01\x05\x06\x10\x01\xff\xff\x99\x97\x00\x55\x01\x70')
        )

        assertInvalid(b'\x12' * 15)
        assertInvalid(b'\x12' * 17)
        assertInvalid(b'\x12' * 4)

    # XXX The following don't test module-level functionality...

    def testSockName(self):
        # Testing getsockname()
        port = support.find_unused_port()
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.addCleanup(sock.close)
        sock.bind(("0.0.0.0", port))
        name = sock.getsockname()
        # XXX(nnorwitz): http://tinyurl.com/os5jz seems to indicate
        # it reasonable to get the host's addr in addition to 0.0.0.0.
        # At least for eCos.  This is required for the S/390 to pass.
        try:
            my_ip_addr = socket.gethostbyname(socket.gethostname())
        except OSError:
            # Probably name lookup wasn't set up right; skip this test
            return
        self.assertIn(name[0], ("0.0.0.0", my_ip_addr), '%s invalid' % name[0])
        self.assertEqual(name[1], port)

    def testGetSockOpt(self):
        # Testing getsockopt()
        # We know a socket should start without reuse==0
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.addCleanup(sock.close)
        reuse = sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR)
        self.assertFalse(reuse != 0, "initial mode is reuse")

    def testSetSockOpt(self):
        # Testing setsockopt()
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.addCleanup(sock.close)
        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
        reuse = sock.getsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR)
        self.assertFalse(reuse == 0, "failed to set reuse mode")

    def testSendAfterClose(self):
        # testing send() after close() with timeout
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.settimeout(1)
        sock.close()
        self.assertRaises(OSError, sock.send, b"spam")

    def testNewAttributes(self):
        # testing .family, .type and .protocol
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        self.assertEqual(sock.family, socket.AF_INET)
        self.assertEqual(sock.type, socket.SOCK_STREAM)
        self.assertEqual(sock.proto, 0)
        sock.close()

    def test_getsockaddrarg(self):
        host = '0.0.0.0'
        port = support.find_unused_port()
        big_port = port + 65536
        neg_port = port - 65536
        sock = socket.socket()
        try:
            self.assertRaises(OverflowError, sock.bind, (host, big_port))
            self.assertRaises(OverflowError, sock.bind, (host, neg_port))
            sock.bind((host, port))
        finally:
            sock.close()

    @unittest.skipUnless(os.name == "nt", "Windows specific")
    def test_sock_ioctl(self):
        self.assertTrue(hasattr(socket.socket, 'ioctl'))
        self.assertTrue(hasattr(socket, 'SIO_RCVALL'))
        self.assertTrue(hasattr(socket, 'RCVALL_ON'))
        self.assertTrue(hasattr(socket, 'RCVALL_OFF'))
        self.assertTrue(hasattr(socket, 'SIO_KEEPALIVE_VALS'))
        s = socket.socket()
        self.addCleanup(s.close)
        self.assertRaises(ValueError, s.ioctl, -1, None)
        s.ioctl(socket.SIO_KEEPALIVE_VALS, (1, 100, 100))

    def testGetaddrinfo(self):
        try:
            socket.getaddrinfo('localhost', 80)
        except socket.gaierror as err:
            if err.errno == socket.EAI_SERVICE:
                # see http://bugs.python.org/issue1282647
                self.skipTest("buggy libc version")
            raise
        # len of every sequence is supposed to be == 5
        for info in socket.getaddrinfo(HOST, None):
            self.assertEqual(len(info), 5)
        # host can be a domain name, a string representation of an
        # IPv4/v6 address or None
        socket.getaddrinfo('localhost', 80)
        socket.getaddrinfo('127.0.0.1', 80)
        socket.getaddrinfo(None, 80)
        if support.IPV6_ENABLED:
            socket.getaddrinfo('::1', 80)
        # port can be a string service name such as "http", a numeric
        # port number or None
        socket.getaddrinfo(HOST, "http")
        socket.getaddrinfo(HOST, 80)
        socket.getaddrinfo(HOST, None)
        # test family and socktype filters
        infos = socket.getaddrinfo(HOST, None, socket.AF_INET)
        for family, _, _, _, _ in infos:
            self.assertEqual(family, socket.AF_INET)
        infos = socket.getaddrinfo(HOST, None, 0, socket.SOCK_STREAM)
        for _, socktype, _, _, _ in infos:
            self.assertEqual(socktype, socket.SOCK_STREAM)
        # test proto and flags arguments
        socket.getaddrinfo(HOST, None, 0, 0, socket.SOL_TCP)
        socket.getaddrinfo(HOST, None, 0, 0, 0, socket.AI_PASSIVE)
        # a server willing to support both IPv4 and IPv6 will
        # usually do this
        socket.getaddrinfo(None, 0, socket.AF_UNSPEC, socket.SOCK_STREAM, 0,
                           socket.AI_PASSIVE)
        # test keyword arguments
        a = socket.getaddrinfo(HOST, None)
        b = socket.getaddrinfo(host=HOST, port=None)
        self.assertEqual(a, b)
        a = socket.getaddrinfo(HOST, None, socket.AF_INET)
        b = socket.getaddrinfo(HOST, None, family=socket.AF_INET)
        self.assertEqual(a, b)
        a = socket.getaddrinfo(HOST, None, 0, socket.SOCK_STREAM)
        b = socket.getaddrinfo(HOST, None, type=socket.SOCK_STREAM)
        self.assertEqual(a, b)
        a = socket.getaddrinfo(HOST, None, 0, 0, socket.SOL_TCP)
        b = socket.getaddrinfo(HOST, None, proto=socket.SOL_TCP)
        self.assertEqual(a, b)
        a = socket.getaddrinfo(HOST, None, 0, 0, 0, socket.AI_PASSIVE)
        b = socket.getaddrinfo(HOST, None, flags=socket.AI_PASSIVE)
        self.assertEqual(a, b)
        a = socket.getaddrinfo(None, 0, socket.AF_UNSPEC, socket.SOCK_STREAM, 0,
                               socket.AI_PASSIVE)
        b = socket.getaddrinfo(host=None, port=0, family=socket.AF_UNSPEC,
                               type=socket.SOCK_STREAM, proto=0,
                               flags=socket.AI_PASSIVE)
        self.assertEqual(a, b)
        # Issue #6697.
        self.assertRaises(UnicodeEncodeError, socket.getaddrinfo, 'localhost', '\uD800')

    def test_getnameinfo(self):
        # only IP addresses are allowed
        self.assertRaises(OSError, socket.getnameinfo, ('mail.python.org',0), 0)

    @unittest.skipUnless(support.is_resource_enabled('network'),
                         'network is not enabled')
    def test_idna(self):
        # Check for internet access before running test (issue #12804).
        try:
            socket.gethostbyname('python.org')
        except socket.gaierror as e:
            if e.errno == socket.EAI_NODATA:
                self.skipTest('internet access required for this test')
        # these should all be successful
        socket.gethostbyname('испытание.python.org')
        socket.gethostbyname_ex('испытание.python.org')
        socket.getaddrinfo('испытание.python.org',0,socket.AF_UNSPEC,socket.SOCK_STREAM)
        # this may not work if the forward lookup choses the IPv6 address, as that doesn't
        # have a reverse entry yet
        # socket.gethostbyaddr('испытание.python.org')

    def check_sendall_interrupted(self, with_timeout):
        # socketpair() is not stricly required, but it makes things easier.
        if not hasattr(signal, 'alarm') or not hasattr(socket, 'socketpair'):
            self.skipTest("signal.alarm and socket.socketpair required for this test")
        # Our signal handlers clobber the C errno by calling a math function
        # with an invalid domain value.
        def ok_handler(*args):
            self.assertRaises(ValueError, math.acosh, 0)
        def raising_handler(*args):
            self.assertRaises(ValueError, math.acosh, 0)
            1 // 0
        c, s = socket.socketpair()
        old_alarm = signal.signal(signal.SIGALRM, raising_handler)
        try:
            if with_timeout:
                # Just above the one second minimum for signal.alarm
                c.settimeout(1.5)
            with self.assertRaises(ZeroDivisionError):
                signal.alarm(1)
                c.sendall(b"x" * (1024**2))
            if with_timeout:
                signal.signal(signal.SIGALRM, ok_handler)
                signal.alarm(1)
                self.assertRaises(socket.timeout, c.sendall, b"x" * (1024**2))
        finally:
            signal.signal(signal.SIGALRM, old_alarm)
            c.close()
            s.close()

    def test_sendall_interrupted(self):
        self.check_sendall_interrupted(False)

    def test_sendall_interrupted_with_timeout(self):
        self.check_sendall_interrupted(True)

    def test_dealloc_warn(self):
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        r = repr(sock)
        with self.assertWarns(ResourceWarning) as cm:
            sock = None
            support.gc_collect()
        self.assertIn(r, str(cm.warning.args[0]))
        # An open socket file object gets dereferenced after the socket
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        f = sock.makefile('rb')
        r = repr(sock)
        sock = None
        support.gc_collect()
        with self.assertWarns(ResourceWarning):
            f = None
            support.gc_collect()

    def test_name_closed_socketio(self):
        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
            fp = sock.makefile("rb")
            fp.close()
            self.assertEqual(repr(fp), "<_io.BufferedReader name=-1>")

    def test_unusable_closed_socketio(self):
        with socket.socket() as sock:
            fp = sock.makefile("rb", buffering=0)
            self.assertTrue(fp.readable())
            self.assertFalse(fp.writable())
            self.assertFalse(fp.seekable())
            fp.close()
            self.assertRaises(ValueError, fp.readable)
            self.assertRaises(ValueError, fp.writable)
            self.assertRaises(ValueError, fp.seekable)

    def test_pickle(self):
        sock = socket.socket()
        with sock:
            for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
                self.assertRaises(TypeError, pickle.dumps, sock, protocol)

    def test_listen_backlog0(self):
        srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        srv.bind((HOST, 0))
        # backlog = 0
        srv.listen(0)
        srv.close()

    @unittest.skipUnless(support.IPV6_ENABLED, 'IPv6 required for this test.')
    def test_flowinfo(self):
        self.assertRaises(OverflowError, socket.getnameinfo,
                          ('::1',0, 0xffffffff), 0)
        with socket.socket(socket.AF_INET6, socket.SOCK_STREAM) as s:
            self.assertRaises(OverflowError, s.bind, ('::1', 0, -10))


@unittest.skipUnless(HAVE_SOCKET_CAN, 'SocketCan required for this test.')
class BasicCANTest(unittest.TestCase):

    def testCrucialConstants(self):
        socket.AF_CAN
        socket.PF_CAN
        socket.CAN_RAW

    def testCreateSocket(self):
        with socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW) as s:
            pass

    def testBindAny(self):
        with socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW) as s:
            s.bind(('', ))

    def testTooLongInterfaceName(self):
        # most systems limit IFNAMSIZ to 16, take 1024 to be sure
        with socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW) as s:
            self.assertRaisesRegex(OSError, 'interface name too long',
                                   s.bind, ('x' * 1024,))

    @unittest.skipUnless(hasattr(socket, "CAN_RAW_LOOPBACK"),
                         'socket.CAN_RAW_LOOPBACK required for this test.')
    def testLoopback(self):
        with socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW) as s:
            for loopback in (0, 1):
                s.setsockopt(socket.SOL_CAN_RAW, socket.CAN_RAW_LOOPBACK,
                             loopback)
                self.assertEqual(loopback,
                    s.getsockopt(socket.SOL_CAN_RAW, socket.CAN_RAW_LOOPBACK))

    @unittest.skipUnless(hasattr(socket, "CAN_RAW_FILTER"),
                         'socket.CAN_RAW_FILTER required for this test.')
    def testFilter(self):
        can_id, can_mask = 0x200, 0x700
        can_filter = struct.pack("=II", can_id, can_mask)
        with socket.socket(socket.PF_CAN, socket.SOCK_RAW, socket.CAN_RAW) as s:
            s.setsockopt(socket.SOL_CAN_RAW, socket.CAN_RAW_FILTER, can_filter)
            self.assertEqual(can_filter,
                    s.getsockopt(socket.SOL_CAN_RAW, socket.CAN_RAW_FILTER, 8))


@unittest.skipUnless(HAVE_SOCKET_CAN, 'SocketCan required for this test.')
@unittest.skipUnless(thread, 'Threading required for this test.')
class CANTest(ThreadedCANSocketTest):

    """The CAN frame structure is defined in <linux/can.h>:

    struct can_frame {
        canid_t can_id;  /* 32 bit CAN_ID + EFF/RTR/ERR flags */
        __u8    can_dlc; /* data length code: 0 .. 8 */
        __u8    data[8] __attribute__((aligned(8)));
    };
    """
    can_frame_fmt = "=IB3x8s"

    def __init__(self, methodName='runTest'):
        ThreadedCANSocketTest.__init__(self, methodName=methodName)

    @classmethod
    def build_can_frame(cls, can_id, data):
        """Build a CAN frame."""
        can_dlc = len(data)
        data = data.ljust(8, b'\x00')
        return struct.pack(cls.can_frame_fmt, can_id, can_dlc, data)

    @classmethod
    def dissect_can_frame(cls, frame):
        """Dissect a CAN frame."""
        can_id, can_dlc, data = struct.unpack(cls.can_frame_fmt, frame)
        return (can_id, can_dlc, data[:can_dlc])

    def testSendFrame(self):
        cf, addr = self.s.recvfrom(self.bufsize)
        self.assertEqual(self.cf, cf)
        self.assertEqual(addr[0], self.interface)
        self.assertEqual(addr[1], socket.AF_CAN)

    def _testSendFrame(self):
        self.cf = self.build_can_frame(0x00, b'\x01\x02\x03\x04\x05')
        self.cli.send(self.cf)

    def testSendMaxFrame(self):
        cf, addr = self.s.recvfrom(self.bufsize)
        self.assertEqual(self.cf, cf)

    def _testSendMaxFrame(self):
        self.cf = self.build_can_frame(0x00, b'\x07' * 8)
        self.cli.send(self.cf)

    def testSendMultiFrames(self):
        cf, addr = self.s.recvfrom(self.bufsize)
        self.assertEqual(self.cf1, cf)

        cf, addr = self.s.recvfrom(self.bufsize)
        self.assertEqual(self.cf2, cf)

    def _testSendMultiFrames(self):
        self.cf1 = self.build_can_frame(0x07, b'\x44\x33\x22\x11')
        self.cli.send(self.cf1)

        self.cf2 = self.build_can_frame(0x12, b'\x99\x22\x33')
        self.cli.send(self.cf2)


@unittest.skipUnless(HAVE_SOCKET_RDS, 'RDS sockets required for this test.')
class BasicRDSTest(unittest.TestCase):

    def testCrucialConstants(self):
        socket.AF_RDS
        socket.PF_RDS

    def testCreateSocket(self):
        with socket.socket(socket.PF_RDS, socket.SOCK_SEQPACKET, 0) as s:
            pass

    def testSocketBufferSize(self):
        bufsize = 16384
        wit…