例程讲解14-WiFi-Shield->mqtt
import usocket as socket
import ustruct as struct
from ubinascii import hexlify
class MQTTException(Exception):
pass
class MQTTClient:
def __init__(self, client_id, server, port=0, user=None, password=None, keepalive=0,
ssl=False, ssl_params={}):
if port == 0:
port = 8883 if ssl else 1883
self.client_id = client_id
self.sock = None
self.server = server
self.port = port
self.ssl = ssl
self.ssl_params = ssl_params
self.pid = 0
self.cb = None
self.user = user
self.pswd = password
self.keepalive = keepalive
self.lw_topic = None
self.lw_msg = None
self.lw_qos = 0
self.lw_retain = False
def _send_str(self, s):
self.sock.send(struct.pack("!H", len(s)))
self.sock.send(s)
def _recv_len(self):
n = 0
sh = 0
while 1:
b = self.sock.recv(1)[0]
n |= (b & 0x7f) << sh
if not b & 0x80:
return n
sh += 7
def set_callback(self, f):
self.cb = f
def set_last_will(self, topic, msg, retain=False, qos=0):
assert 0 <= qos <= 2
assert topic
self.lw_topic = topic
self.lw_msg = msg
self.lw_qos = qos
self.lw_retain = retain
def connect(self, clean_session=True):
self.sock = socket.socket()
addr = None
addr = socket.getaddrinfo(self.server, self.port)[0][-1]
self.sock.connect(addr)
if self.ssl:
import ussl
self.sock = ussl.wrap_socket(self.sock, **self.ssl_params)
premsg = bytearray(b"\x10\0\0\0\0\0")
msg = bytearray(b"\x04MQTT\x04\x02\0\0")
sz = 10 + 2 + len(self.client_id)
msg[6] = clean_session << 1
if self.user is not None:
sz += 2 + len(self.user) + 2 + len(self.pswd)
msg[6] |= 0xC0
if self.keepalive:
assert self.keepalive < 65536
msg[7] |= self.keepalive >> 8
msg[8] |= self.keepalive & 0x00FF
if self.lw_topic:
sz += 2 + len(self.lw_topic) + 2 + len(self.lw_msg)
msg[6] |= 0x4 | (self.lw_qos & 0x1) << 3 | (self.lw_qos & 0x2) << 3
msg[6] |= self.lw_retain << 5
i = 1
while sz > 0x7f:
premsg[i] = (sz & 0x7f) | 0x80
sz >>= 7
i += 1
premsg[i] = sz
self.sock.send(premsg[0:i + 2])
self.sock.send(msg)
self._send_str(self.client_id)
if self.lw_topic:
self._send_str(self.lw_topic)
self._send_str(self.lw_msg)
if self.user is not None:
self._send_str(self.user)
self._send_str(self.pswd)
resp = self.sock.recv(4)
assert resp[0] == 0x20 and resp[1] == 0x02
if resp[3] != 0:
raise MQTTException(resp[3])
return resp[2] & 1
def disconnect(self):
self.sock.send(b"\xe0\0")
self.sock.close()
def ping(self):
self.sock.send(b"\xc0\0")
def publish(self, topic, msg, retain=False, qos=0):
pkt = bytearray(b"\x30\0\0\0")
pkt[0] |= qos << 1 | retain
sz = 2 + len(topic) + len(msg)
if qos > 0:
sz += 2
assert sz < 2097152
i = 1
while sz > 0x7f:
pkt[i] = (sz & 0x7f) | 0x80
sz >>= 7
i += 1
pkt[i] = sz
self.sock.send(pkt[0:i + 1])
self._send_str(topic)
if qos > 0:
self.pid += 1
pid = self.pid
struct.pack_into("!H", pkt, 0, pid)
self.sock.send(pkt[0:2])
self.sock.send(msg)
if qos == 1:
while 1:
op = self.wait_msg()
if op == 0x40:
sz = self.sock.recv(1)
assert sz == b"\x02"
rcv_pid = self.sock.recv(2)
rcv_pid = rcv_pid[0] << 8 | rcv_pid[1]
if pid == rcv_pid:
return
elif qos == 2:
assert 0
def subscribe(self, topic, qos=0):
assert self.cb is not None, "Subscribe callback is not set"
pkt = bytearray(b"\x82\0\0\0")
self.pid += 1
struct.pack_into("!BH", pkt, 1, 2 + 2 + len(topic) + 1, self.pid)
self.sock.send(pkt)
self._send_str(topic)
self.sock.send(qos.to_bytes(1, "little"))
while 1:
op = self.wait_msg()
if op == 0x90:
resp = self.sock.recv(4)
assert resp[1] == pkt[2] and resp[2] == pkt[3]
if resp[3] == 0x80:
raise MQTTException(resp[3])
return
def wait_msg(self):
res = self.sock.recv(1)
self.sock.setblocking(True)
if res is None:
return None
if res == b"":
raise OSError(-1)
if res == b"\xd0":
sz = self.sock.recv(1)[0]
assert sz == 0
return None
op = res[0]
if op & 0xf0 != 0x30:
return op
sz = self._recv_len()
topic_len = self.sock.recv(2)
topic_len = (topic_len[0] << 8) | topic_len[1]
topic = self.sock.recv(topic_len)
sz -= topic_len + 2
if op & 6:
pid = self.sock.recv(2)
pid = pid[0] << 8 | pid[1]
sz -= 2
msg = self.sock.recv(sz)
self.cb(topic, msg)
if op & 6 == 2:
pkt = bytearray(b"\x40\x02\0\0")
struct.pack_into("!H", pkt, 2, pid)
self.sock.send(pkt)
elif op & 6 == 4:
assert 0
def check_msg(self):
self.sock.setblocking(False)
return self.wait_msg()
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