mosquitto.py

# Copyright (c) 2012,2013 Roger Light <roger@atchoo.org>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# 1. Redistributions of source code must retain the above copyright notice,
#    this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 3. Neither the name of mosquitto nor the names of its
#    contributors may be used to endorse or promote products derived from
#    this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
#
#
# This product includes software developed by the OpenSSL Project for use in
# the OpenSSL Toolkit. (http://www.openssl.org/)
# This product includes cryptographic software written by Eric Young
# (eay@cryptsoft.com)
# This product includes software written by Tim Hudson (tjh@cryptsoft.com)

"""
This is an MQTT v3.1 client module. MQTT is a lightweight pub/sub messaging
protocol that is easy to implement and suitable for low powered devices.
"""
import errno
import platform
import random
import select
import socket
import ssl
import struct
import sys
import threading
import time

MOSQUITTO_MAJOR=1
MOSQUITTO_MINOR=2
MOSQUITTO_REVISION=3
MOSQUITTO_VERSION_NUMBER=(MOSQUITTO_MAJOR*1000000+MOSQUITTO_MINOR*1000+MOSQUITTO_REVISION)

EAGAIN = errno.EAGAIN

if sys.version_info[0] < 3:
    PROTOCOL_NAME = "MQIsdp"
else:
    PROTOCOL_NAME = b"MQIsdp"

PROTOCOL_VERSION = 3

# Message types
CONNECT = 0x10
CONNACK = 0x20
PUBLISH = 0x30
PUBACK = 0x40
PUBREC = 0x50
PUBREL = 0x60
PUBCOMP = 0x70
SUBSCRIBE = 0x80
SUBACK = 0x90
UNSUBSCRIBE = 0xA0
UNSUBACK = 0xB0
PINGREQ = 0xC0
PINGRESP = 0xD0
DISCONNECT = 0xE0

# Log levels
MOSQ_LOG_INFO = 0x01
MOSQ_LOG_NOTICE = 0x02
MOSQ_LOG_WARNING = 0x04
MOSQ_LOG_ERR = 0x08
MOSQ_LOG_DEBUG = 0x10

# CONNACK codes
CONNACK_ACCEPTED = 0
CONNACK_REFUSED_PROTOCOL_VERSION = 1
CONNACK_REFUSED_IDENTIFIER_REJECTED = 2
CONNACK_REFUSED_SERVER_UNAVAILABLE = 3
CONNACK_REFUSED_BAD_USERNAME_PASSWORD = 4
CONNACK_REFUSED_NOT_AUTHORIZED = 5

# Connection state
mosq_cs_new = 0
mosq_cs_connected = 1
mosq_cs_disconnecting = 2
mosq_cs_connect_async = 3

# Message direction
mosq_md_invalid = 0
mosq_md_in = 1
mosq_md_out = 2

# Message state
mosq_ms_invalid = 0,
mosq_ms_wait_puback = 1
mosq_ms_wait_pubrec = 2
mosq_ms_wait_pubrel = 3
mosq_ms_wait_pubcomp = 4

# Error values
MOSQ_ERR_AGAIN = -1
MOSQ_ERR_SUCCESS = 0
MOSQ_ERR_NOMEM = 1
MOSQ_ERR_PROTOCOL = 2
MOSQ_ERR_INVAL = 3
MOSQ_ERR_NO_CONN = 4
MOSQ_ERR_CONN_REFUSED = 5
MOSQ_ERR_NOT_FOUND = 6
MOSQ_ERR_CONN_LOST = 7
MOSQ_ERR_TLS = 8
MOSQ_ERR_PAYLOAD_SIZE = 9
MOSQ_ERR_NOT_SUPPORTED = 10
MOSQ_ERR_AUTH = 11
MOSQ_ERR_ACL_DENIED = 12
MOSQ_ERR_UNKNOWN = 13
MOSQ_ERR_ERRNO = 14


def _fix_sub_topic(subtopic):
    # Convert ////some////over/slashed///topic/etc/etc//
    # into some/over/slashed/topic/etc/etc
    if subtopic[0] == '/':
        return '/'+'/'.join(filter(None, subtopic.split('/')))
    else:
        return '/'.join(filter(None, subtopic.split('/')))


def error_string(mosq_errno):
    """Return the error string associated with a mosquitto error number."""
    if mosq_errno == MOSQ_ERR_SUCCESS:
        return "No error."
    elif mosq_errno == MOSQ_ERR_NOMEM:
        return "Out of memory."
    elif mosq_errno == MOSQ_ERR_PROTOCOL:
        return "A network protocol error occurred when communicating with the broker."
    elif mosq_errno == MOSQ_ERR_INVAL:
        return "Invalid function arguments provided."
    elif mosq_errno == MOSQ_ERR_NO_CONN:
        return "The client is not currently connected."
    elif mosq_errno == MOSQ_ERR_CONN_REFUSED:
        return "The connection was refused."
    elif mosq_errno == MOSQ_ERR_NOT_FOUND:
        return "Message not found (internal error)."
    elif mosq_errno == MOSQ_ERR_CONN_LOST:
        return "The connection was lost."
    elif mosq_errno == MOSQ_ERR_TLS:
        return "A TLS error occurred."
    elif mosq_errno == MOSQ_ERR_PAYLOAD_SIZE:
        return "Payload too large."
    elif mosq_errno == MOSQ_ERR_NOT_SUPPORTED:
        return "This feature is not supported."
    elif mosq_errno == MOSQ_ERR_AUTH:
        return "Authorisation failed."
    elif mosq_errno == MOSQ_ERR_ACL_DENIED:
        return "Access denied by ACL."
    elif mosq_errno == MOSQ_ERR_UNKNOWN:
        return "Unknown error."
    elif mosq_errno == MOSQ_ERR_ERRNO:
        return "Error defined by errno."
    else:
        return "Unknown error."


def connack_string(connack_code):
    """Return the string associated with a CONNACK result."""
    if connack_code == 0:
        return "Connection Accepted."
    elif connack_code == 1:
        return "Connection Refused: unacceptable protocol version."
    elif connack_code == 2:
        return "Connection Refused: identifier rejected."
    elif connack_code == 3:
        return "Connection Refused: broker unavailable."
    elif connack_code == 4:
        return "Connection Refused: bad user name or password."
    elif connack_code == 5:
        return "Connection Refused: not authorised."
    else:
        return "Connection Refused: unknown reason."


def topic_matches_sub(sub, topic):
    """Check whether a topic matches a subscription.

    For example:

    foo/bar would match the subscription foo/# or +/bar
    non/matching would not match the subscription non/+/+
    """
    result = True
    local_sub = _fix_sub_topic(sub)
    local_topic = _fix_sub_topic(topic)
    multilevel_wildcard = False

    slen = len(local_sub)
    tlen = len(local_topic)

    spos = 0
    tpos = 0

    while spos < slen and tpos < tlen:
        if local_sub[spos] == local_topic[tpos]:
            spos += 1
            tpos += 1
        else:
            if local_sub[spos] == '+':
                spos += 1
                while tpos < tlen and local_topic[tpos] != '/':
                    tpos += 1
                if tpos == tlen and spos == slen:
                    result = True
                    break

            elif local_sub[spos] == '#':
                multilevel_wildcard = True
                if spos+1 != slen:
                    result = False
                    break
                else:
                    result = True
                    break

            else:
                result = False
                break

        if tpos == tlen-1:
            # Check for e.g. foo matching foo/#
            if spos == slen-3 and local_sub[spos+1] == '/' and local_sub[spos+2] == '#':
                result = True
                multilevel_wildcard = True
                break

    if not multilevel_wildcard and (tpos < tlen or spos < slen):
        result = False

    return result


class MosquittoMessage:
    """ This is a class that describes an incoming message. It is passed to the
    on_message callback as the message parameter.

    Members:

    topic : String. topic that the message was published on.
    payload : String/bytes the message payload.
    qos : Integer. The message Quality of Service 0, 1 or 2.
    retain : Boolean. If true, the message is a retained message and not fresh.
    mid : Integer. The message id.
    """
    def __init__(self):
        self.timestamp = 0
        self.direction = mosq_md_invalid
        self.state = mosq_ms_invalid
        self.dup = False
        self.mid = 0
        self.topic = ""
        self.payload = None
        self.qos = 0
        self.retain = False


class MosquittoInPacket:
    """Internal datatype."""
    def __init__(self):
        self.command = 0
        self.have_remaining = 0
        self.remaining_count = []
        self.remaining_mult = 1
        self.remaining_length = 0
        self.packet = b""
        self.to_process = 0
        self.pos = 0

    def cleanup(self):
        self.__init__()


class MosquittoPacket:
    """Internal datatype."""
    def __init__(self, command, packet, mid, qos):
        self.command = command
        self.mid = mid
        self.qos = qos
        self.pos = 0
        self.to_process = len(packet)
        self.packet = packet


class Mosquitto:
    """MQTT version 3.1 client class.

    This is the main class for use communicating with an MQTT broker.

    General usage flow:

    * Use connect()/connect_async() to connect to a broker
    * Call loop() frequently to maintain network traffic flow with the broker
    * Or use loop_start() to set a thread running to call loop() for you.
    * Or use loop_forever() to handle calling loop() for you in a blocking
    * function.
    * Use subscribe() to subscribe to a topic and receive messages
    * Use publish() to send messages
    * Use disconnect() to disconnect from the broker

    Data returned from the broker is made available with the use of callback
    functions as described below.

    Callbacks
    =========

    A number of callback functions are available to receive data back from the
    broker. To use a callback, define a function and then assign it to the
    client:

    def on_connect(mosq, userdata, rc):
        print("Connection returned " + str(rc))

    client.on_connect = on_connect

    All of the callbacks as described below have a "mosq" and an "userdata"
    argument. "mosq" is the Mosquitto instance that is calling the callback.
    "userdata" is user data of any type and can be set when creating a new
    client instance or with user_data_set(userdata).

    The callbacks:

    on_connect(mosq, userdata, rc): called when the broker responds to our
      connection request. The value of rc determines success or not:
      0: Connection successful
      1: Connection refused - incorrect protocol version
      2: Connection refused - invalid client identifier
      3: Connection refused - server unavailable
      4: Connection refused - bad username or password
      5: Connection refused - not authorised
      6-255: Currently unused.

    on_disconnect(mosq, userdata, rc): called when the client disconnects from
      the broker. The rc parameter indicates the disconnection state. If
      MOSQ_ERR_SUCCESS (0), the callback was called in response to a
      disconnect() call. If any other value the disconnection was unexpected,
      such as might be caused by a network error.

    on_message(mosq, userdata, message): called when a message has been
      received on a topic that the client subscribes to. The message variable
      is a MosquittoMessage that describes all of the message parameters.

    on_publish(mosq, userdata, mid): called when a message that was to be sent
      using the publish() call has completed transmission to the broker. For
      messages with QoS levels 1 and 2, this means that the appropriate
      handshakes have completed. For QoS 0, this simply means that the message
      has left the client. The mid variable matches the mid variable returned
      from the corresponding publish() call, to allow outgoing messages to be
      tracked.  This callback is important because even if the publish() call
      returns success, it does not always mean that the message has been sent.

    on_subscribe(mosq, userdata, mid, granted_qos): called when the broker
      responds to a subscribe request. The mid variable matches the mid
      variable returned from the corresponding subscribe() call. The
      granted_qos variable is a list of integers that give the QoS level the
      broker has granted for each of the different subscription requests.

    on_unsubscribe(mosq, userdata, mid): called when the broker responds to an
      unsubscribe request. The mid variable matches the mid variable returned
      from the corresponding unsubscribe() call.

    on_log(mosq, userdata, level, buf): called when the client has log
      information. Define to allow debugging. The level variable gives the
      severity of the message and will be one of MOSQ_LOG_INFO,
      MOSQ_LOG_NOTICE, MOSQ_LOG_WARNING, MOSQ_LOG_ERR, and MOSQ_LOG_DEBUG. The
      message itself is in buf.

    """
    def __init__(self, client_id="", clean_session=True, userdata=None):
        """client_id is the unique client id string used when connecting to the
        broker. If client_id is zero length or None, then one will be randomly
        generated. In this case, clean_session must be True. If this is not the
        case a ValueError will be raised.

        clean_session is a boolean that determines the client type. If True,
        the broker will remove all information about this client when it
        disconnects. If False, the client is a persistent client and
        subscription information and queued messages will be retained when the
        client disconnects.
        Note that a client will never discard its own outgoing messages on
        disconnect. Calling connect() or reconnect() will cause the messages to
        be resent.  Use reinitialise() to reset a client to its original state.

        userdata is user defined data of any type that is passed as the
        "userdata" parameter to callbacks. It may be updated at a later point
        with the user_data_set() function.
        """
        if not clean_session and (client_id == "" or client_id is None):
            raise ValueError('A client id must be provided if clean session is False.')

        self._userdata = userdata
        self._sock = None
        self._keepalive = 60
        self._message_retry = 20
        self._last_retry_check = 0
        self._clean_session = clean_session
        if client_id == "" or client_id is None:
            self._client_id = "mosq/" + "".join(random.choice("0123456789ADCDEF") for x in range(23-5))
        else:
            self._client_id = client_id

        self._username = ""
        self._password = ""
        self._in_packet = MosquittoInPacket()
        self._out_packet = []
        self._current_out_packet = None
        self._last_msg_in = time.time()
        self._last_msg_out = time.time()
        self._ping_t = 0
        self._last_mid = 0
        self._state = mosq_cs_new
        self._messages = []
        self._max_inflight_messages = 20
        self._inflight_messages = 0
        self._will = False
        self._will_topic = ""
        self._will_payload = None
        self._will_qos = 0
        self._will_retain = False
        self.on_disconnect = None
        self.on_connect = None
        self.on_publish = None
        self.on_message = None
        self.on_subscribe = None
        self.on_unsubscribe = None
        self.on_log = None
        self._host = ""
        self._port = 1883
        self._bind_address = ""
        self._in_callback = False
        self._strict_protocol = False
        self._callback_mutex = threading.Lock()
        self._state_mutex = threading.Lock()
        self._out_packet_mutex = threading.Lock()
        self._current_out_packet_mutex = threading.Lock()
        self._msgtime_mutex = threading.Lock()
        self._message_mutex = threading.Lock()
        self._thread = None
        self._thread_terminate = False
        self._ssl = None
        self._tls_certfile = None
        self._tls_keyfile = None
        self._tls_ca_certs = None
        self._tls_cert_reqs = None
        self._tls_ciphers = None
        self._tls_insecure = False
        self._reconnect_delay = 1
        self._reconnect_delay_max = 1
        self._reconnect_exponential_backoff = False

    def __del__(self):
        pass

    def reinitialise(self, client_id="", clean_session=True, userdata=None):
        if self._ssl:
            self._ssl.close()
            self._ssl = None
            self._sock = None
        elif self._sock:
            self._sock.close()
            self._sock = None
        self.__init__(client_id, clean_session, userdata)

    def tls_set(self, ca_certs, certfile=None, keyfile=None, cert_reqs=ssl.CERT_REQUIRED, tls_version=ssl.PROTOCOL_TLSv1, ciphers=None):
        """Configure network encryption and authentication options. Enables SSL/TLS support.

        ca_certs : a string path to the Certificate Authority certificate files
        that are to be treated as trusted by this client. If this is the only
        option given then the client will operate in a similar manner to a web
        browser. That is to say it will require the broker to have a
        certificate signed by the Certificate Authorities in ca_certs and will
        communicate using TLS v1, but will not attempt any form of
        authentication. This provides basic network encryption but may not be
        sufficient depending on how the broker is configured.

        certfile and keyfile are strings pointing to the PEM encoded client
        certificate and private keys respectively. If these arguments are not
        None then they will be used as client information for TLS based
        authentication.  Support for this feature is broker dependent. Note
        that if either of these files in encrypted and needs a password to
        decrypt it, Python will ask for the password at the command line. It is
        not currently possible to define a callback to provide the password.

        cert_reqs allows the certificate requirements that the client imposes
        on the broker to be changed. By default this is ssl.CERT_REQUIRED,
        which means that the broker must provide a certificate. See the ssl
        pydoc for more information on this parameter.

        tls_version allows the version of the SSL/TLS protocol used to be
        specified. By default TLS v1 is used. Previous versions (all versions
        beginning with SSL) are possible but not recommended due to possible
        security problems.

        ciphers is a string specifying which encryption ciphers are allowable
        for this connection, or None to use the defaults. See the ssl pydoc for
        more information.

        Must be called before connect() or connect_async()."""
        if sys.version < '2.7':
            raise ValueError('Python 2.7 is the minimum supported version for TLS.')

        if ca_certs is None:
            raise ValueError('ca_certs must not be None.')

        try:
            f = open(ca_certs, "r")
        except IOError as err:
            raise IOError(ca_certs+": "+err.strerror)
        else:
            f.close()
        if certfile is not None:
            try:
                f = open(certfile, "r")
            except IOError as err:
                raise IOError(certfile+": "+err.strerror)
            else:
                f.close()
        if keyfile is not None:
            try:
                f = open(keyfile, "r")
            except IOError as err:
                raise IOError(keyfile+": "+err.strerror)
            else:
                f.close()

        self._tls_ca_certs = ca_certs
        self._tls_certfile = certfile
        self._tls_keyfile = keyfile
        self._tls_cert_reqs = cert_reqs
        self._tls_version = tls_version
        self._tls_ciphers = ciphers

    def tls_insecure_set(self, value):
        """Configure verification of the server hostname in the server certificate.

        If value is set to true, it is impossible to guarantee that the host
        you are connecting to is not impersonating your server. This can be
        useful in initial server testing, but makes it possible for a malicious
        third party to impersonate your server through DNS spoofing, for
        example.

        Do not use this function in a real system. Setting value to true means
        there is no point using encryption.

        Must be called before connect()."""
        self._tls_insecure = value

    def connect(self, host, port=1883, keepalive=60, bind_address=""):
        """Connect to a remote broker.

        host is the hostname or IP address of the remote broker.
        port is the network port of the server host to connect to. Defaults to
        1883. Note that the default port for MQTT over SSL/TLS is 8883 so if
        you are using tls_set() the port may need providing.
        keepalive: Maximum period in seconds between communications with the
        broker. If no other messages are being exchanged, this controls the
        rate at which the client will send ping messages to the broker.
        """
        self.connect_async(host, port, keepalive, bind_address)
        return self.reconnect()

    def connect_async(self, host, port=1883, keepalive=60, bind_address=""):
        """Connect to a remote broker asynchronously. This is a non-blocking
        connect call that can be used with loop_start() to provide very quick
        start.

        host is the hostname or IP address of the remote broker.
        port is the network port of the server host to connect to. Defaults to
        1883. Note that the default port for MQTT over SSL/TLS is 8883 so if
        you are using tls_set() the port may need providing.
        keepalive: Maximum period in seconds between communications with the
        broker. If no other messages are being exchanged, this controls the
        rate at which the client will send ping messages to the broker.
        """
        if host is None or len(host) == 0:
            raise ValueError('Invalid host.')
        if port <= 0:
            raise ValueError('Invalid port number.')
        if keepalive < 0:
            raise ValueError('Keepalive must be >=0.')
        if bind_address != "" and bind_address is not None:
            if (sys.version_info[0] == 2 and sys.version_info[1] < 7) or (sys.version_info[0] == 3 and sys.version_info[1] < 2):
                raise ValueError('bind_address requires Python 2.7 or 3.2.')

        self._host = host
        self._port = port
        self._keepalive = keepalive
        self._bind_address = bind_address

        self._state_mutex.acquire()
        self._state = mosq_cs_connect_async
        self._state_mutex.release()

    def reconnect(self):
        """Reconnect the client after a disconnect. Can only be called after
        connect()/connect_async()."""
        if len(self._host) == 0:
            raise ValueError('Invalid host.')
        if self._port <= 0:
            raise ValueError('Invalid port number.')

        self._in_packet.cleanup()
        self._out_packet_mutex.acquire()
        self._out_packet = []
        self._out_packet_mutex.release()

        self._current_out_packet_mutex.acquire()
        self._current_out_packet = None
        self._current_out_packet_mutex.release()

        self._msgtime_mutex.acquire()
        self._last_msg_in = time.time()
        self._last_msg_out = time.time()
        self._msgtime_mutex.release()

        self._ping_t = 0
        self._state_mutex.acquire()
        self._state = mosq_cs_new
        self._state_mutex.release()
        if self._ssl:
            self._ssl.close()
            self._ssl = None
            self._sock = None
        elif self._sock:
            self._sock.close()
            self._sock = None

        # Put messages in progress in a valid state.
        self._messages_reconnect_reset()

        try:
            if (sys.version_info[0] == 2 and sys.version_info[1] < 7) or (sys.version_info[0] == 3 and sys.version_info[1] < 2):
                self._sock = socket.create_connection((self._host, self._port), source_address=(self._bind_address, 0))
            else:
                self._sock = socket.create_connection((self._host, self._port))
        except socket.error as err:
            (msg) = err
            if msg.errno != errno.EINPROGRESS:
                raise

        if self._tls_ca_certs is not None:
            self._ssl = ssl.wrap_socket(
                self._sock,
                certfile=self._tls_certfile,
                keyfile=self._tls_keyfile,
                ca_certs=self._tls_ca_certs,
                cert_reqs=self._tls_cert_reqs,
                ssl_version=self._tls_version,
                ciphers=self._tls_ciphers)

            if self._tls_insecure is False:
                if sys.version_info[0] < 3 or (sys.version_info[0] == 3 and sys.version_info[1] < 2):
                    self._tls_match_hostname()
                else:
                    ssl.match_hostname(self._ssl.getpeercert(), self._host)

        self._sock.setblocking(0)

        return self._send_connect(self._keepalive, self._clean_session)

    def loop(self, timeout=1.0, max_packets=1):
        """Process network events.

        This function must be called regularly to ensure communication with the
        broker is carried out. It calls select() on the network socket to wait
        for network events. If incoming data is present it will then be
        processed. Outgoing commands, from e.g. publish(), are normally sent
        immediately that their function is called, but this is not always
        possible. loop() will also attempt to send any remaining outgoing
        messages, which also includes commands that are part of the flow for
        messages with QoS>0.

        timeout: The time in seconds to wait for incoming/outgoing network
          traffic before timing out and returning.
        max_packets: Not currently used.

        Returns MOSQ_ERR_SUCCESS on success.
        Returns >0 on error.

        A ValueError will be raised if timeout < 0"""
        if timeout < 0.0:
            raise ValueError('Invalid timeout.')

        self._current_out_packet_mutex.acquire()
        self._out_packet_mutex.acquire()
        if self._current_out_packet is None and len(self._out_packet) > 0:
            self._current_out_packet = self._out_packet.pop(0)

        if self._current_out_packet:
            wlist = [self.socket()]
        else:
            wlist = []
        self._out_packet_mutex.release()
        self._current_out_packet_mutex.release()

        rlist = [self.socket()]
        try:
            socklist = select.select(rlist, wlist, [], timeout)
        except TypeError:
            # Socket isn't correct type, in likelihood connection is lost
            return MOSQ_ERR_CONN_LOST

        if self.socket() in socklist[0]:
            rc = self.loop_read(max_packets)
            if rc or (self._ssl is None and self._sock is None):
                return rc

        if self.socket() in socklist[1]:
            rc = self.loop_write(max_packets)
            if rc or (self._ssl is None and self._sock is None):
                return rc

        return self.loop_misc()

    def publish(self, topic, payload=None, qos=0, retain=False):
        """Publish a message on a topic.

        This causes a message to be sent to the broker and subsequently from
        the broker to any clients subscribing to matching topics.

        topic: The topic that the message should be published on.
        payload: The actual message to send. If not given, or set to None a
        zero length message will be used. Passing an int or float will result
        in the payload being converted to a string representing that number. If
        you wish to send a true int/float, use struct.pack() to create the
        payload you require.
        qos: The quality of service level to use.
        retain: If set to true, the message will be set as the "last known
        good"/retained message for the topic.

        Returns a tuple (result, mid), where result is MOSQ_ERR_SUCCESS to
        indicate success or MOSQ_ERR_NO_CONN if the client is not currently
        connected.  mid is the message ID for the publish request. The mid
        value can be used to track the publish request by checking against the
        mid argument in the on_publish() callback if it is defined.

        A ValueError will be raised if topic is None, has zero length or is
        invalid (contains a wildcard), if qos is not one of 0, 1 or 2, or if
        the length of the payload is greater than 268435455 bytes."""
        if topic is None or len(topic) == 0:
            raise ValueError('Invalid topic.')
        if qos<0 or qos>2:
            raise ValueError('Invalid QoS level.')
        if isinstance(payload, str) or isinstance(payload, bytearray):
            local_payload = payload
        elif isinstance(payload, int) or isinstance(payload, float):
            local_payload = str(payload)
        elif payload is None:
            local_payload = None
        else:
            raise TypeError('payload must be a string, bytearray, int, float or None.')

        if local_payload is not None and len(local_payload) > 268435455:
            raise ValueError('Payload too large.')

        if self._topic_wildcard_len_check(topic) != MOSQ_ERR_SUCCESS:
            raise ValueError('Publish topic cannot contain wildcards.')

        local_mid = self._mid_generate()

        if qos == 0:
            rc = self._send_publish(local_mid, topic, local_payload, qos, retain, False)
            return (rc, local_mid)
        else:
            message = MosquittoMessage()
            message.timestamp = time.time()
            message.direction = mosq_md_out

            message.mid = local_mid
            message.topic = topic
            if local_payload is None or len(local_payload) == 0:
                message.payload = None
            else:
                message.payload = local_payload

            message.qos = qos
            message.retain = retain
            message.dup = False

            self._message_mutex.acquire()
            self._messages.append(message)
            if self._max_inflight_messages == 0 or self._inflight_messages < self._max_inflight_messages:
                self._inflight_messages = self._inflight_messages+1
                if qos == 1:
                    message.state = mosq_ms_wait_puback
                elif qos == 2:
                    message.state = mosq_ms_wait_pubrec
                self._message_mutex.release()

                rc = self._send_publish(message.mid, message.topic, message.payload, message.qos, message.retain, message.dup)
                return (rc, local_mid)
            self._message_mutex.release()
            return (MOSQ_ERR_SUCCESS, local_mid)

    def username_pw_set(self, username, password=None):
        """Set a username and optionally a password for broker authentication.

        Must be called before connect() to have any effect.
        Requires a broker that supports MQTT v3.1.

        username: The username to authenticate with. Need have no relationship
                  to the client id.
        password: The password to authenticate with. Optional, set to None if
                  not required.
        """
        self._username = username
        self._password = password

    def disconnect(self):
        """Disconnect a connected client from the broker."""
        self._state_mutex.acquire()
        self._state = mosq_cs_disconnecting
        self._state_mutex.release()

        if self._sock is None and self._ssl is None:
            return MOSQ_ERR_NO_CONN

        return self._send_disconnect()

    def subscribe(self, topic, qos=0):
        """Subscribe the client to a topic.

        sub: The subscription topic to subscribe to.
        qos: The desired quality of service level for the subscription.

        Returns a tuple (result, mid), where result is MOSQ_ERR_SUCCESS
        to indicate success or MOSQ_ERR_NO_CONN if the client is not currently
        connected.
        mid is the message ID for the subscribe request. The mid value can be
        used to track the subscribe request by checking against the mid
        argument in the on_subscribe() callback if it is defined.

        Raises a ValueError if qos is not 0, 1 or 2, or if topic is None or has
        zero string length.
        """
        if qos<0 or qos>2:
            raise ValueError('Invalid QoS level.')
        if topic is None or len(topic) == 0:
            raise ValueError('Invalid topic.')
        topic = _fix_sub_topic(topic)

        if self._sock is None and self._ssl is None:
            return MOSQ_ERR_NO_CONN

        return self._send_subscribe(False, topic, qos)

    def unsubscribe(self, topic):
        """Unsubscribe the client from a topic.

        sub: The subscription topic to unsubscribe from.

        Returns a tuple (result, mid), where result is MOSQ_ERR_SUCCESS
        to indicate success or MOSQ_ERR_NO_CONN if the client is not currently
        connected.
        mid is the message ID for the unsubscribe request. The mid value can be
        used to track the unsubscribe request by checking against the mid
        argument in the on_unsubscribe() callback if it is defined.

        Raises a ValueError if topic is None or has zero string length.
        """
        if topic is None or len(topic) == 0:
            raise ValueError('Invalid topic.')
        topic = _fix_sub_topic(topic)
        if self._sock is None and self._ssl is None:
            return MOSQ_ERR_NO_CONN

        return self._send_unsubscribe(False, topic)

    def loop_read(self, max_packets=1):
        """Process read network events. Use in place of calling loop() if you
        wish to handle your client reads as part of your own application.

        Use socket() to obtain the client socket to call select() or equivalent
        on.

        Do not use if you are using the threaded interface loop_start()."""
        if self._sock is None and self._ssl is None:
            return MOSQ_ERR_NO_CONN

        max_packets = len(self._messages)
        if max_packets < 1:
            max_packets = 1

        for i in range(0, max_packets):
            rc = self._packet_read()
            if rc > 0:
                return self._loop_rc_handle(rc)
            elif rc == MOSQ_ERR_AGAIN:
                return MOSQ_ERR_SUCCESS
        return MOSQ_ERR_SUCCESS

    def loop_write(self, max_packets=1):
        """Process read network events. Use in place of calling loop() if you
        wish to handle your client reads as part of your own application.

        Use socket() to obtain the client socket to call select() or equivalent
        on.

        Use want_write() to determine if there is data waiting to be written.

        Do not use if you are using the threaded interface loop_start()."""
        if self._sock is None and self._ssl is None:
            return MOSQ_ERR_NO_CONN

        max_packets = len(self._messages)
        if max_packets < 1:
            max_packets = 1

        for i in range(0, max_packets):
            rc = self._packet_write()
            if rc > 0:
                return self._loop_rc_handle(rc)
            elif rc == MOSQ_ERR_AGAIN:
                return MOSQ_ERR_SUCCESS
        return MOSQ_ERR_SUCCESS

    def want_write(self):
        """Call to determine if there is network data waiting to be written.
        Useful if you are calling select() yourself rather than using loop().
        """
        if self._current_out_packet or len(self._out_packet) > 0:
            return True
        else:
            return False

    def loop_misc(self):
        """Process miscellaneous network events. Use in place of calling loop()
        if you wish to call select() or equivalent on.

        Do not use if you are using the threaded interface loop_start()."""
        if self._sock is None and self._ssl is None:
            return MOSQ_ERR_NO_CONN

        now = time.time()
        self._check_keepalive()
        if self._last_retry_check+1 < now:
            # Only check once a second at most
            self._message_retry_check()
            self._last_retry_check = now

        if self._ping_t > 0 and now - self._ping_t >= self._keepalive:
            # mosq->ping_t != 0 means we are waiting for a pingresp.
            # This hasn't happened in the keepalive time so we should
            # disconnect.
            if self._ssl:
                self._ssl.close()
                self._ssl = None
            elif self._sock:
                self._sock.close()
                self._sock = None

            self._callback_mutex.acquire()
            if self._state == mosq_cs_disconnecting:
                rc = MOSQ_ERR_SUCCESS
            else:
                rc = 1
            if self.on_disconnect:
                self._in_callback = True
                self.on_disconnect(self, self._userdata, rc)
                self._in_callback = False
            self._callback_mutex.release()
            return MOSQ_ERR_CONN_LOST

        return MOSQ_ERR_SUCCESS

    def max_inflight_messages_set(self, inflight):
        """Set the maximum number of messages with QoS>0 that can be part way
        through their network flow at once. Defaults to 20."""
        if inflight < 0:
            raise ValueError('Invalid inflight.')
        self._max_inflight_messages = inflight

    def message_retry_set(self, retry):
        """Set the timeout in seconds before a message with QoS>0 is retried.
        20 seconds by default."""
        if retry < 0:
            raise ValueError('Invalid retry.')

        self._message_retry = retry

    def reconnect_delay_set(self, delay, delay_max, exponential_backoff):
        """Set the amount of time that the client will wait before reconnecting
        after losing its connection to the broker.

        delay is the number of seconds to wait between successive reconnect
        attempts. By default this is set to 1.

        delay_max is the maximum number of seconds to wait between reconnection
        attempts and is also set to 1 by default. This means that the default
        behaviour is to attempt to reconnect every second.

        If exponential_backoff is False and delay_max is greater than delay,
        then on each successive reconnect failure the delay will increase
        linearly in the form delay*failure_count.

        If exponential_backoff is True and delay_max is greater than delay,
        then on each successive reconnect failure the delay will increase
        exponentially in the form delay*failure_count^2.

        In both cases, the maximum delay ever used is set by delay_max.

        Example 1:
            delay=2, delay_max=10, exponential_backoff=False

            Delays would be: 2, 4, 6, 8, 10, 10, ...

        Example 2:
            delay=3, delay_max=30, exponential_backoff=True

            Delays would be: 3, 6, 12, 24, 30, 30, ...
        """
        if not isinstance(delay, int) or delay <= 0:
            ValueError("delay must be a positive integer.")
        if not isinstance(delay_max, int) or delay_max < delay:
            ValueError("delay_max must be a integer and greater than delay.")
        if not isinstance(exponential_backoff, bool):
            ValueError("exponential_backoff must be a bool.")

        self._reconnect_delay = delay
        self._reconnect_delay_max = delay_max
        self._reconnect_exponential_backoff = exponential_backoff

    def user_data_set(self, userdata):
        """Set the user data variable passed to callbacks. May be any data
        type."""
        self._userdata = userdata

    def will_set(self, topic, payload=None, qos=0, retain=False):
        """Set a Will to be sent by the broker in case the client disconnects
        unexpectedly.

        This must be called before connect() to have any effect.

        topic: The topic that the will message should be published on.
        payload: The message to send as a will. If not given, or set to None a
        zero length message will be used as the will. Passing an int or float
        will result in the payload being converted to a string representing
        that number. If you wish to send a true int/float, use struct.pack() to
        create the payload you require.
        qos: The quality of service level to use for the will.
        retain: If set to true, the will message will be set as the "last known
        good"/retained message for the topic.

        Raises a ValueError if qos is not 0, 1 or 2, or if topic is None or has
        zero string length.
        """
        if topic is None or len(topic) == 0:
            raise ValueError('Invalid topic.')
        if qos<0 or qos>2:
            raise ValueError('Invalid QoS level.')
        if isinstance(payload, str) or isinstance(payload, bytearray):
            self._will_payload = payload
        elif isinstance(payload, int) or isinstance(payload, float):
            self._will_payload = str(payload)
        elif payload is None:
            self._will_payload = None
        else:
            raise TypeError('payload must be a string, bytearray, int, float or None.')

        self._will = True
        self._will_topic = topic
        self._will_qos = qos
        self._will_retain = retain

    def will_clear(self):
        """ Removes a will that was previously configured with will_set().

        Must be called before connect() to have any effect."""
        self._will = False
        self._will_topic = ""
        self._will_payload = None
        self._will_qos = 0
        self._will_retain = False

    def socket(self):
        """Return the socket or ssl object for this client."""
        if self._ssl:
            return self._ssl
        else:
            return self._sock

    def loop_forever(self, timeout=1.0, max_packets=1):
        """This function call loop() for you in an infinite blocking loop. It
        is useful for the case where you only want to run the MQTT client loop
        in your program.

        loop_forever() will handle reconnecting for you. If you call
        disconnect() in a callback it will return."""

        reconnects = 0
        run = True
        if self._state == mosq_cs_connect_async:
            self.reconnect()

        while run:
            rc = MOSQ_ERR_SUCCESS
            while rc == MOSQ_ERR_SUCCESS:
                rc = self.loop(timeout, max_packets)
                # We don't need to worry about locking here, because we've
                # either called loop_forever() when in single threaded mode, or
                # in multi threaded mode when loop_stop() has been called and
                # so no other threads can access _current_out_packet,
                # _out_packet or _messages.
                if (self._thread_terminate
                        and self._current_out_packet == None
                        and len(self._out_packet) == 0
                        and len(self._messages) == 0):

                    rc = 1
                    run = False
                if rc == MOSQ_ERR_SUCCESS:
                    reconnects = 0

            self._state_mutex.acquire()
            if self._state == mosq_cs_disconnecting:
                run = False
                self._state_mutex.release()
            else:
                self._state_mutex.release()
                if self._reconnect_delay > 0 and self._reconnect_exponential_backoff:
                    reconnect_delay = self._reconnect_delay*reconnects*reconnects
                else:
                    reconnect_delay = self._reconnect_delay

                if reconnect_delay > self._reconnect_delay_max:
                    reconnect_delay = self._reconnect_delay_max
                else:
                    reconnects = reconnects + 1

                time.sleep(reconnect_delay)

                self._state_mutex.acquire()
                if self._state == mosq_cs_disconnecting:
                    run = False
                    self._state_mutex.release()
                else:
                    self._state_mutex.release()
                    try:
                        self.reconnect()
                    except socket.error as err:
                        pass
        return rc

    def loop_start(self):
        """This is part of the threaded client interface. Call this once to
        start a new thread to process network traffic. This provides an
        alternative to repeatedly calling loop() yourself.
        """
        if self._thread is not None:
            return MOSQ_ERR_INVAL

        self._thread = threading.Thread(target=self._thread_main)
        self._thread.daemon = True
        self._thread.start()

    def loop_stop(self, force=False):
        """This is part of the threaded client interface. Call this once to
        stop the network thread previously created with loop_start(). This call
        will block until the network thread finishes.

        The force parameter is currently ignored.
        """
        if self._thread is None:
            return MOSQ_ERR_INVAL

        self._thread_terminate = True
        self._thread.join()
        self._thread = None

    # ============================================================
    # Private functions
    # ============================================================

    def _loop_rc_handle(self, rc):
        if rc:
            if self._ssl:
                self._ssl.close()
                self._ssl = None
            elif self._sock:
                self._sock.close()
                self._sock = None

            self._state_mutex.acquire()
            if self._state == mosq_cs_disconnecting:
                rc = MOSQ_ERR_SUCCESS
            self._state_mutex.release()
            self._callback_mutex.acquire()
            if self.on_disconnect:
                self._in_callback = True
                self.on_disconnect(self, self._userdata, rc)
                self._in_callback = False

            self._callback_mutex.release()
        return rc

    def _packet_read(self):
        # This gets called if pselect() indicates that there is network data
        # available - ie. at least one byte.  What we do depends on what data
        # we already have.
        # If we've not got a command, attempt to read one and save it. This
        # should always work because it's only a single byte.
        # Then try to read the remaining length. This may fail because it is
        # may be more than one byte - will need to save data pending next read
        # if it does fail.
        # Then try to read the remaining payload, where 'payload' here means
        # the combined variable header and actual payload. This is the most
        # likely to fail due to longer length, so save current data and current
        # position.  After all data is read, send to _mosquitto_handle_packet()
        # to deal with.  Finally, free the memory and reset everything to
        # starting conditions.
        if self._in_packet.command == 0:
            try:
                if self._ssl:
                    command = self._ssl.read(1)
                else:
                    command = self._sock.recv(1)
            except socket.error as err:
                (msg) = err
                if self._ssl and (msg.errno == ssl.SSL_ERROR_WANT_READ or msg.errno == ssl.SSL_ERROR_WANT_WRITE):
                    return MOSQ_ERR_AGAIN
                if msg.errno == EAGAIN:
                    return MOSQ_ERR_AGAIN
                raise
            else:
                if len(command) == 0:
                    return 1
                command = struct.unpack("!B", command)
                self._in_packet.command = command[0]

        if self._in_packet.have_remaining == 0:
            # Read remaining
            # Algorithm for decoding taken from pseudo code in the spec.
            while True:
                try:
                    if self._ssl:
                        byte = self._ssl.read(1)
                    else:
                        byte = self._sock.recv(1)
                except socket.error as err:
                    (msg) = err
                    if self._ssl and (msg.errno == ssl.SSL_ERROR_WANT_READ or msg.errno == ssl.SSL_ERROR_WANT_WRITE):
                        return MOSQ_ERR_AGAIN
                    if msg.errno == EAGAIN:
                        return MOSQ_ERR_AGAIN
                    raise
                else:
                    byte = struct.unpack("!B", byte)
                    byte = byte[0]
                    self._in_packet.remaining_count.append(byte)
                    # Max 4 bytes length for remaining length as defined by
                    # protocol.  Anything more likely means a broken/malicious
                    # client.
                    if len(self._in_packet.remaining_count) > 4:
                        return MOSQ_ERR_PROTOCOL

                    self._in_packet.remaining_length = self._in_packet.remaining_length + (byte & 127)*self._in_packet.remaining_mult
                    self._in_packet.remaining_mult = self._in_packet.remaining_mult * 128

                if (byte & 128) == 0:
                    break

            self._in_packet.have_remaining = 1
            self._in_packet.to_process = self._in_packet.remaining_length

        while self._in_packet.to_process > 0:
            try:
                if self._ssl:
                    data = self._ssl.read(self._in_packet.to_process)
                else:
                    data = self._sock.recv(self._in_packet.to_process)
            except socket.error as err:
                (msg) = err
                if self._ssl and (msg.errno == ssl.SSL_ERROR_WANT_READ or msg.errno == ssl.SSL_ERROR_WANT_WRITE):
                    return MOSQ_ERR_AGAIN
                if msg.errno == EAGAIN:
                    return MOSQ_ERR_AGAIN
                raise
            else:
                self._in_packet.to_process = self._in_packet.to_process - len(data)
                self._in_packet.packet = self._in_packet.packet + data

        # All data for this packet is read.
        self._in_packet.pos = 0
        rc = self._packet_handle()

        # Free data and reset values
        self._in_packet.cleanup()

        self._msgtime_mutex.acquire()
        self._last_msg_in = time.time()
        self._msgtime_mutex.release()
        return rc

    def _packet_write(self):
        self._current_out_packet_mutex.acquire()

        while self._current_out_packet:
            packet = self._current_out_packet

            try:
                if self._ssl:
                    write_length = self._ssl.write(packet.packet[packet.pos:])
                else:
                    write_length = self._sock.send(packet.packet[packet.pos:])
            except AttributeError:
                self._current_out_packet_mutex.release()
                return MOSQ_ERR_SUCCESS
            except socket.error as err:
                self._current_out_packet_mutex.release()
                (msg) = err
                if self._ssl and (msg.errno == ssl.SSL_ERROR_WANT_READ or msg.errno == ssl.SSL_ERROR_WANT_WRITE):
                    return MOSQ_ERR_AGAIN
                if msg.errno == EAGAIN:
                    return MOSQ_ERR_AGAIN
                raise

            if write_length > 0:
                packet.to_process = packet.to_process - write_length
                packet.pos = packet.pos + write_length

                if packet.to_process == 0:
                    if (packet.command & 0xF0) == PUBLISH and packet.qos == 0:
                        self._callback_mutex.acquire()
                        if self.on_publish:
                            self._in_callback = True
                            self.on_publish(self, self._userdata, packet.mid)
                            self._in_callback = False

                        self._callback_mutex.release()

                    self._out_packet_mutex.acquire()
                    if len(self._out_packet) > 0:
                        self._current_out_packet = self._out_packet.pop(0)
                    else:
                        self._current_out_packet = None
                    self._out_packet_mutex.release()
            else:
                pass  # FIXME

        self._current_out_packet_mutex.release()

        self._msgtime_mutex.acquire()
        self._last_msg_out = time.time()
        self._msgtime_mutex.release()

        return MOSQ_ERR_SUCCESS

    def _easy_log(self, level, buf):
        if self.on_log:
            self.on_log(self, self._userdata, level, buf)

    def _check_keepalive(self):
        now = time.time()
        self._msgtime_mutex.acquire()
        last_msg_out = self._last_msg_out
        last_msg_in = self._last_msg_in
        self._msgtime_mutex.release()
        if (self._sock is not None or self._ssl is not None) and (now - last_msg_out >= self._keepalive or now - last_msg_in >= self._keepalive):
            if self._state == mosq_cs_connected and self._ping_t == 0:
                self._send_pingreq()
                self._msgtime_mutex.acquire()
                self._last_msg_out = now
                self._last_msg_in = now
                self._msgtime_mutex.release()
            else:
                if self._ssl:
                    self._ssl.close()
                    self._ssl = None
                elif self._sock:
                    self._sock.close()
                    self._sock = None

                if self._state == mosq_cs_disconnecting:
                    rc = MOSQ_ERR_SUCCESS
                else:
                    rc = 1
                self._callback_mutex.acquire()
                if self.on_disconnect:
                    self._in_callback = True
                    self.on_disconnect(self, self._userdata, rc)
                    self._in_callback = False
                self._callback_mutex.release()

    def _mid_generate(self):
        self._last_mid = self._last_mid + 1
        if self._last_mid == 65536:
            self._last_mid = 1
        return self._last_mid

    def _topic_wildcard_len_check(self, topic):
        # Search for + or # in a topic. Return MOSQ_ERR_INVAL if found.
         # Also returns MOSQ_ERR_INVAL if the topic string is too long.
         # Returns MOSQ_ERR_SUCCESS if everything is fine.
        if '+' in topic or '#' in topic or len(topic) == 0 or len(topic) > 65535:
            return MOSQ_ERR_INVAL
        else:
            return MOSQ_ERR_SUCCESS

    def _send_pingreq(self):
        self._easy_log(MOSQ_LOG_DEBUG, "Sending PINGREQ")
        rc = self._send_simple_command(PINGREQ)
        if rc == MOSQ_ERR_SUCCESS:
            self._ping_t = time.time()
        return rc

    def _send_pingresp(self):
        self._easy_log(MOSQ_LOG_DEBUG, "Sending PINGRESP")
        return self._send_simple_command(PINGRESP)

    def _send_puback(self, mid):
        self._easy_log(MOSQ_LOG_DEBUG, "Sending PUBACK (Mid: "+str(mid)+")")
        return self._send_command_with_mid(PUBACK, mid, False)

    def _send_pubcomp(self, mid):
        self._easy_log(MOSQ_LOG_DEBUG, "Sending PUBCOMP (Mid: "+str(mid)+")")
        return self._send_command_with_mid(PUBCOMP, mid, False)

    def _pack_remaining_length(self, packet, remaining_length):
        remaining_bytes = []
        while True:
            byte = remaining_length % 128
            remaining_length = remaining_length // 128
            # If there are more digits to encode, set the top bit of this digit
            if remaining_length > 0:
                byte = byte | 0x80

            remaining_bytes.append(byte)
            packet.extend(struct.pack("!B", byte))
            if remaining_length == 0:
                # FIXME - this doesn't deal with incorrectly large payloads
                return packet

    def _pack_str16(self, packet, data):
        if sys.version_info[0] < 3:
            if isinstance(data, bytearray):
                packet.extend(struct.pack("!H", len(data)))
                packet.extend(data)
            elif isinstance(data, str):
                pack_format = "!H" + str(len(data)) + "s"
                packet.extend(struct.pack(pack_format, len(data), data))
            elif isinstance(data, unicode):
                udata = data.encode('utf-8')
                pack_format = "!H" + str(len(udata)) + "s"
                packet.extend(struct.pack(pack_format, len(udata), udata))
            else:
                raise TypeError
        else:
            if isinstance(data, bytearray):
                packet.extend(struct.pack("!H", len(data)))
                packet.extend(data)
            elif isinstance(data, str):
                udata = data.encode('utf-8')
                pack_format = "!H" + str(len(udata)) + "s"
                packet.extend(struct.pack(pack_format, len(udata), udata))
            else:
                raise TypeError

    def _send_publish(self, mid, topic, payload=None, qos=0, retain=False, dup=False):
        if self._sock is None and self._ssl is None:
            return MOSQ_ERR_NO_CONN

        command = PUBLISH | ((dup&0x1)<<3) | (qos<<1) | retain
        packet = bytearray()
        packet.extend(struct.pack("!B", command))
        if payload is None:
            remaining_length = 2+len(topic)
            self._easy_log(MOSQ_LOG_DEBUG, "Sending PUBLISH (d"+str(dup)+", q"+str(qos)+", r"+str(int(retain))+", m"+str(mid)+", '"+topic+"' (NULL payload)")
        else:
            remaining_length = 2+len(topic) + len(payload)
            self._easy_log(MOSQ_LOG_DEBUG, "Sending PUBLISH (d"+str(dup)+", q"+str(qos)+", r"+str(int(retain))+", m"+str(mid)+", '"+topic+"', ... ("+str(len(payload))+" bytes)")

        if qos > 0:
            # For message id
            remaining_length = remaining_length + 2

        self._pack_remaining_length(packet, remaining_length)
        self._pack_str16(packet, topic)

        if qos > 0:
            # For message id
            packet.extend(struct.pack("!H", mid))

        if payload is not None:
            if isinstance(payload, str):
                if sys.version_info[0] < 3:
                    pack_format = str(len(payload)) + "s"
                    packet.extend(struct.pack(pack_format, payload))
                else:
                    upayload = payload.encode('utf-8')
                    pack_format = str(len(upayload)) + "s"
                    packet.extend(struct.pack(pack_format, upayload))
            elif isinstance(payload, bytearray):
                packet.extend(payload)
            elif isinstance(payload, unicode):
                    upayload = payload.encode('utf-8')
                    pack_format = str(len(upayload)) + "s"
                    packet.extend(struct.pack(pack_format, upayload))
            else:
                raise TypeError('payload must be a string, unicode or a bytearray.')

        return self._packet_queue(PUBLISH, packet, mid, qos)

    def _send_pubrec(self, mid):
        self._easy_log(MOSQ_LOG_DEBUG, "Sending PUBREC (Mid: "+str(mid)+")")
        return self._send_command_with_mid(PUBREC, mid, False)

    def _send_pubrel(self, mid, dup=False):
        self._easy_log(MOSQ_LOG_DEBUG, "Sending PUBREL (Mid: "+str(mid)+")")
        return self._send_command_with_mid(PUBREL|2, mid, dup)

    def _send_command_with_mid(self, command, mid, dup):
        # For PUBACK, PUBCOMP, PUBREC, and PUBREL
        if dup:
            command = command | 8

        remaining_length = 2
        packet = struct.pack('!BBH', command, remaining_length, mid)
        return self._packet_queue(command, packet, mid, 1)

    def _send_simple_command(self, command):
        # For DISCONNECT, PINGREQ and PINGRESP
        remaining_length = 0
        packet = struct.pack('!BB', command, remaining_length)
        return self._packet_queue(command, packet, 0, 0)

    def _send_connect(self, keepalive, clean_session):
        remaining_length = 12 + 2+len(self._client_id)
        connect_flags = 0
        if clean_session:
            connect_flags = connect_flags | 0x02

        if self._will:
            if self._will_payload is not None:
                remaining_length = remaining_length + 2+len(self._will_topic) + 2+len(self._will_payload)
            else:
                remaining_length = remaining_length + 2+len(self._will_topic) + 2

            connect_flags = connect_flags | 0x04 | ((self._will_qos&0x03) << 3) | ((self._will_retain&0x01) << 5)

        if self._username:
            remaining_length = remaining_length + 2+len(self._username)
            connect_flags = connect_flags | 0x80
            if self._password:
                connect_flags = connect_flags | 0x40
                remaining_length = remaining_length + 2+len(self._password)

        command = CONNECT
        packet = bytearray()
        packet.extend(struct.pack("!B", command))
        self._pack_remaining_length(packet, remaining_length)
        packet.extend(struct.pack("!H6sBBH", len(PROTOCOL_NAME), PROTOCOL_NAME, PROTOCOL_VERSION, connect_flags, keepalive))

        self._pack_str16(packet, self._client_id)

        if self._will:
            self._pack_str16(packet, self._will_topic)
            if self._will_payload is None or len(self._will_payload) == 0:
                packet.extend(struct.pack("!H", 0))
            else:
                self._pack_str16(packet, self._will_payload)

        if self._username:
            self._pack_str16(packet, self._username)

            if self._password:
                self._pack_str16(packet, self._password)

        self._keepalive = keepalive
        return self._packet_queue(command, packet, 0, 0)

    def _send_disconnect(self):
        return self._send_simple_command(DISCONNECT)

    def _send_subscribe(self, dup, topic, topic_qos):
        remaining_length = 2 + 2+len(topic) + 1
        command = SUBSCRIBE | (dup<<3) | (1<<1)
        packet = bytearray()
        packet.extend(struct.pack("!B", command))
        self._pack_remaining_length(packet, remaining_length)
        local_mid = self._mid_generate()
        packet.extend(struct.pack("!H", local_mid))
        self._pack_str16(packet, topic)
        packet.extend(struct.pack("B", topic_qos))
        return (self._packet_queue(command, packet, local_mid, 1), local_mid)

    def _send_unsubscribe(self, dup, topic):
        remaining_length = 2 + 2+len(topic)
        command = UNSUBSCRIBE | (dup<<3) | (1<<1)
        packet = bytearray()
        packet.extend(struct.pack("!B", command))
        self._pack_remaining_length(packet, remaining_length)
        local_mid = self._mid_generate()
        packet.extend(struct.pack("!H", local_mid))
        self._pack_str16(packet, topic)
        return (self._packet_queue(command, packet, local_mid, 1), local_mid)

    def _message_update(self, mid, direction, state):
        self._message_mutex.acquire()
        for m in self._messages:
            if m.mid == mid and m.direction == direction:
                m.state = state
                m.timestamp = time.time()
                self._message_mutex.release()
                return MOSQ_ERR_SUCCESS

        self._message_mutex.release()
        return MOSQ_ERR_NOT_FOUND

    def _message_retry_check(self):
        self._message_mutex.acquire()
        now = time.time()
        for m in self._messages:
            if m.timestamp + self._message_retry < now:
                if m.state == mosq_ms_wait_puback or m.state == mosq_ms_wait_pubrec:
                    m.timestamp = now
                    m.dup = True
                    self._send_publish(m.mid, m.topic, m.payload, m.qos, m.retain, m.dup)
                elif m.state == mosq_ms_wait_pubrel:
                    m.timestamp = now
                    m.dup = True
                    self._send_pubrec(m.mid)
                elif m.state == mosq_ms_wait_pubcomp:
                    m.timestamp = now
                    m.dup = True
                    self._send_pubrel(m.mid, True)
        self._message_mutex.release()

    def _messages_reconnect_reset(self):
        self._message_mutex.acquire()
        for m in self._messages:
            m.timestamp = 0
            if m.direction == mosq_md_out:
                if self._max_inflight_messages == 0 or self._inflight_messages < self._max_inflight_messages:
                    if m.qos == 1:
                        m.state = mosq_ms_wait_puback
                    elif m.qos == 2:
                        # Preserve current state
                        pass
                else:
                    m.state = mosq_ms_invalid
            else:
                if m.qos != 2:
                    self._messages.pop(self._messages.index(m))
                else:
                    # Preserve current state
                    pass
        self._message_mutex.release()

    def _packet_queue(self, command, packet, mid, qos):
        mpkt = MosquittoPacket(command, packet, mid, qos)

        self._out_packet_mutex.acquire()
        self._out_packet.append(mpkt)
        if self._current_out_packet_mutex.acquire(False):
            if self._current_out_packet is None and len(self._out_packet) > 0:
                self._current_out_packet = self._out_packet.pop(0)
            self._current_out_packet_mutex.release()
        self._out_packet_mutex.release()

        if not self._in_callback and self._thread is None:
            return self.loop_write()
        else:
            return MOSQ_ERR_SUCCESS

    def _packet_handle(self):
        cmd = self._in_packet.command&0xF0
        if cmd == PINGREQ:
            return self._handle_pingreq()
        elif cmd == PINGRESP:
            return self._handle_pingresp()
        elif cmd == PUBACK:
            return self._handle_pubackcomp("PUBACK")
        elif cmd == PUBCOMP:
            return self._handle_pubackcomp("PUBCOMP")
        elif cmd == PUBLISH:
            return self._handle_publish()
        elif cmd == PUBREC:
            return self._handle_pubrec()
        elif cmd == PUBREL:
            return self._handle_pubrel()
        elif cmd == CONNACK:
            return self._handle_connack()
        elif cmd == SUBACK:
            return self._handle_suback()
        elif cmd == UNSUBACK:
            return self._handle_unsuback()
        else:
            # If we don't recognise the command, return an error straight away.
            self._easy_log(MOSQ_LOG_ERR, "Error: Unrecognised command "+str(cmd))
            return MOSQ_ERR_PROTOCOL

    def _handle_pingreq(self):
        if self._strict_protocol:
            if self._in_packet.remaining_length != 0:
                return MOSQ_ERR_PROTOCOL

        self._easy_log(MOSQ_LOG_DEBUG, "Received PINGREQ")
        return self._send_pingresp()

    def _handle_pingresp(self):
        if self._strict_protocol:
            if self._in_packet.remaining_length != 0:
                return MOSQ_ERR_PROTOCOL

        # No longer waiting for a PINGRESP.
        self._ping_t = 0
        self._easy_log(MOSQ_LOG_DEBUG, "Received PINGRESP")
        return MOSQ_ERR_SUCCESS

    def _handle_connack(self):
        if self._strict_protocol:
            if self._in_packet.remaining_length != 2:
                return MOSQ_ERR_PROTOCOL

        if len(self._in_packet.packet) != 2:
            return MOSQ_ERR_PROTOCOL

        (resvd, result) = struct.unpack("!BB", self._in_packet.packet)
        self._easy_log(MOSQ_LOG_DEBUG, "Received CONNACK ("+str(resvd)+", "+str(result)+")")
        self._callback_mutex.acquire()
        if self.on_connect:
            self._in_callback = True
            self.on_connect(self, self._userdata, result)
            self._in_callback = False
        self._callback_mutex.release()
        if result == 0:
            self._state = mosq_cs_connected
            return MOSQ_ERR_SUCCESS
        elif result > 0 and result < 6:
            return MOSQ_ERR_CONN_REFUSED
        else:
            return MOSQ_ERR_PROTOCOL

    def _handle_suback(self):
        self._easy_log(MOSQ_LOG_DEBUG, "Received SUBACK")
        pack_format = "!H" + str(len(self._in_packet.packet)-2) + 's'
        (mid, packet) = struct.unpack(pack_format, self._in_packet.packet)
        pack_format = "!" + "B"*len(packet)
        granted_qos = struct.unpack(pack_format, packet)

        self._callback_mutex.acquire()
        if self.on_subscribe:
            self._in_callback = True
            self.on_subscribe(self, self._userdata, mid, granted_qos)
            self._in_callback = False
        self._callback_mutex.release()

        return MOSQ_ERR_SUCCESS

    def _handle_publish(self):
        rc = 0

        header = self._in_packet.command
        message = MosquittoMessage()
        message.direction = mosq_md_in
        message.dup = (header & 0x08)>>3
        message.qos = (header & 0x06)>>1
        message.retain = (header & 0x01)

        pack_format = "!H" + str(len(self._in_packet.packet)-2) + 's'
        (slen, packet) = struct.unpack(pack_format, self._in_packet.packet)
        pack_format = '!' + str(slen) + 's' + str(len(packet)-slen) + 's'
        (message.topic, packet) = struct.unpack(pack_format, packet)

        if len(message.topic) == 0:
            return MOSQ_ERR_PROTOCOL

        if sys.version_info[0] >= 3:
            message.topic = message.topic.decode('utf-8')
        message.topic = _fix_sub_topic(message.topic)

        if message.qos > 0:
            pack_format = "!H" + str(len(packet)-2) + 's'
            (message.mid, packet) = struct.unpack(pack_format, packet)

        message.payload = packet

        self._easy_log(
            MOSQ_LOG_DEBUG,
            "Received PUBLISH (d"+str(message.dup)+
            ", q"+str(message.qos)+", r"+str(message.retain)+
            ", m"+str(message.mid)+", '"+message.topic+
            "', ...  ("+str(len(message.payload))+" bytes)")

        message.timestamp = time.time()
        if message.qos == 0:
            self._callback_mutex.acquire()
            if self.on_message:
                self._in_callback = True
                self.on_message(self, self._userdata, message)
                self._in_callback = False

            self._callback_mutex.release()
            return MOSQ_ERR_SUCCESS
        elif message.qos == 1:
            rc = self._send_puback(message.mid)
            self._callback_mutex.acquire()
            if self.on_message:
                self._in_callback = True
                self.on_message(self, self._userdata, message)
                self._in_callback = False

            self._callback_mutex.release()
            return rc
        elif message.qos == 2:
            rc = self._send_pubrec(message.mid)
            message.state = mosq_ms_wait_pubrel
            self._message_mutex.acquire()
            self._messages.append(message)
            self._message_mutex.release()
            return rc
        else:
            return MOSQ_ERR_PROTOCOL

    def _handle_pubrel(self):
        if self._strict_protocol:
            if self._in_packet.remaining_length != 2:
                return MOSQ_ERR_PROTOCOL

        if len(self._in_packet.packet) != 2:
            return MOSQ_ERR_PROTOCOL

        mid = struct.unpack("!H", self._in_packet.packet)
        mid = mid[0]
        self._easy_log(MOSQ_LOG_DEBUG, "Received PUBREL (Mid: "+str(mid)+")")

        self._message_mutex.acquire()
        for i in range(len(self._messages)):
            if self._messages[i].direction == mosq_md_in and self._messages[i].mid == mid:

                # Only pass the message on if we have removed it from the queue - this
                # prevents multiple callbacks for the same message.
                self._callback_mutex.acquire()
                if self.on_message:
                    self._in_callback = True
                    self.on_message(self, self._userdata, self._messages[i])
                    self._in_callback = False
                self._callback_mutex.release()
                self._messages.pop(i)
                self._inflight_messages = self._inflight_messages - 1
                if self._max_inflight_messages > 0:
                    rc = self._update_inflight()
                    if rc != MOSQ_ERR_SUCCESS:
                        self._message_mutex.release()
                        return rc

                self._message_mutex.release()
                return self._send_pubcomp(mid)

        self._message_mutex.release()
        return MOSQ_ERR_SUCCESS

    def _update_inflight(self):
        # Dont lock message_mutex here
        for m in self._messages:
            if self._inflight_messages < self._max_inflight_messages:
                if m.qos > 0 and m.state == mosq_ms_invalid and m.direction == mosq_md_out:
                    self._inflight_messages = self._inflight_messages + 1
                    if m.qos == 1:
                        m.state = mosq_ms_wait_puback
                    elif m.qos == 2:
                        m.state = mosq_ms_wait_pubrec
                    rc = self._send_publish(m.mid, m.topic, m.payload, m.qos, m.retain, m.dup)
                    if rc != 0:
                        return rc
            else:
                return MOSQ_ERR_SUCCESS
        return MOSQ_ERR_SUCCESS

    def _handle_pubrec(self):
        if self._strict_protocol:
            if self._in_packet.remaining_length != 2:
                return MOSQ_ERR_PROTOCOL

        mid = struct.unpack("!H", self._in_packet.packet)
        mid = mid[0]
        self._easy_log(MOSQ_LOG_DEBUG, "Received PUBREC (Mid: "+str(mid)+")")

        self._message_mutex.acquire()
        for m in self._messages:
            if m.direction == mosq_md_out and m.mid == mid:
                m.state = mosq_ms_wait_pubcomp
                m.timestamp = time.time()
                self._message_mutex.release()
                return self._send_pubrel(mid, False)

        self._message_mutex.release()
        return MOSQ_ERR_SUCCESS

    def _handle_unsuback(self):
        if self._strict_protocol:
            if self._in_packet.remaining_length != 2:
                return MOSQ_ERR_PROTOCOL

        mid = struct.unpack("!H", self._in_packet.packet)
        mid = mid[0]
        self._easy_log(MOSQ_LOG_DEBUG, "Received UNSUBACK (Mid: "+str(mid)+")")
        self._callback_mutex.acquire()
        if self.on_unsubscribe:
            self._in_callback = True
            self.on_unsubscribe(self, self._userdata, mid)
            self._in_callback = False
        self._callback_mutex.release()
        return MOSQ_ERR_SUCCESS

    def _handle_pubackcomp(self, cmd):
        if self._strict_protocol:
            if self._in_packet.remaining_length != 2:
                return MOSQ_ERR_PROTOCOL

        mid = struct.unpack("!H", self._in_packet.packet)
        mid = mid[0]
        self._easy_log(MOSQ_LOG_DEBUG, "Received "+cmd+" (Mid: "+str(mid)+")")

        self._message_mutex.acquire()
        for i in range(len(self._messages)):
            try:
                if self._messages[i].direction == mosq_md_out and self._messages[i].mid == mid:
                    # Only inform the client the message has been sent once.
                    self._callback_mutex.acquire()
                    if self.on_publish:
                        self._in_callback = True
                        self.on_publish(self, self._userdata, mid)
                        self._in_callback = False

                    self._callback_mutex.release()
                    self._messages.pop(i)
                    self._inflight_messages = self._inflight_messages - 1
                    if self._max_inflight_messages > 0:
                        rc = self._update_inflight()
                        if rc != MOSQ_ERR_SUCCESS:
                            self._message_mutex.release()
                            return rc
                    self._message_mutex.release()
                    return MOSQ_ERR_SUCCESS
            except IndexError:
                # Have removed item so i>count.
                # Not really an error.
                pass

        self._message_mutex.release()
        return MOSQ_ERR_SUCCESS

    def _thread_main(self):
        self._thread_terminate = False
        self._state_mutex.acquire()
        if self._state == mosq_cs_connect_async:
            self._state_mutex.release()
            self.reconnect()
        else:
            self._state_mutex.release()

        self.loop_forever()

    def _tls_match_hostname(self):
        cert = self._ssl.getpeercert()
        san = cert.get('subjectAltName')
        if san:
            have_san_dns = False
            for ((key, value)) in san:
                if key == 'DNS':
                    have_san_dns = True
                    if value == self._host:
                        return
                if key == 'IP Address':
                    have_san_dns = True
                    if value.lower() == self._host.lower():
                        return

            if have_san_dns:
                # Only check subject if subjectAltName dns not found.
                raise ssl.SSLError('Certificate subject does not match remote hostname.')
        subject = cert.get('subject')
        if subject:
            for ((key, value),) in subject:
                if key == 'commonName':
                    if value.lower() == self._host.lower():
                        return

        raise ssl.SSLError('Certificate subject does not match remote hostname.')