init

dnssd.py

+import usocket
+import utime
+import uselect
+
+#TYPEs
+TYPE_A   = 1
+TYPE_PTR = 12
+TYPE_TXT = 16
+TYPE_SRV = 33
+TYPE_AAAA= 28
+
+#Make request
+def str2dnsstr(string):
+  strings = string.split(b'.')
+  return b''.join((bytes((len(x),)) + x for x in strings))+b'\0'
+
+def makeServiceQuery(service):
+  query  = bytes((0, 0,  #ID
+                  0, 0,  #Flage (Query,...)
+                  0, 1,  #One question
+                  0, 0,  #No Answer
+                  0, 0,  #NScount
+                  0, 0)) #ARcount
+  query += str2dnsstr(service)
+  query += bytes((0x00, 0x0C,  #PTR record
+                  0x80, 0x01)) #Unicast, Query Class: INternet
+  return query
+
+def uint16(x):
+  return (x[0]<<8)+x[1]
+
+#parse answer
+def parseDNSstring(data, i, r=''):
+  #print(data[i:])
+  qname = b''
+  if data and len(data) > i:
+    while data[i]:
+      #print(r+'parsing 1:', i, hex(data[i]))
+      if data[i] & 0xc0:
+        p = uint16(data[i:i+2])&0x3FFF
+        if p > i:
+          print('weird pointer, p>i', p, i)
+          return None
+        #print(r+'recurse', p)
+        ret = parseDNSstring(data, p, r=' '+r)
+        #print(r+'back', ret)
+        if ret:
+          return qname+ret[0], i+2
+        else:
+          return ret
+      elif len(data) > (data[i]+i):
+        qname += data[i+1:i+1+(data[i])] + b'.'
+        #print(r+'qname+=', data[i+1:i+1+(data[i])])
+        i += (data[i]+1)
+      else:
+        return None
+    if qname:
+      return qname[:-1], i+1
+    else:
+      return None #no valid data
+  return None
+
+def parsePacket(data):
+  if len(data) < 13:
+    return None
+  if not data[2] & 0x80: #not an answer
+    return None
+  if data[2] & 0x02: #data truncated, ignore for now
+    return None
+  if not data[7]: #Zero answers
+    return None
+  
+  questions = uint16(data[4:6])
+  answers   = uint16(data[6:8])
+  
+  #data = data[12:]
+  i = 12
+  
+  for q in range(questions):
+    ret = parseDNSstring(data, i)
+    if ret:
+      qname, d = ret
+      i = d
+    else:
+      return None #invalid Data
+    
+    qtype = uint16(data[i:i+2])
+    i += 2
+    print('qtype:', hex(qtype))
+    qclass = uint16(data[i:i+2])
+    i += 2
+    print('qclass', hex(qclass))
+  
+  adict = {'A': [], 'AAAA': [], 'SRV': [], 'TXT': [], 'PTR': []}
+  
+  for a in range(answers):
+    #print('\nanswer', a+1, '/', answers)
+    if len(data) < i+12: #incomplete data
+      return None
+
+    ret = parseDNSstring(data, i)
+    if ret:
+      aname, d = ret
+      i = d
+    else:
+      return None
+    #print("aname:", aname)
+
+    atype = uint16(data[i:i+2])
+    i += 2
+    #print('atype:', hex(atype))
+    aclass = uint16(data[i:i+2])&0x7FFF
+    i += 2
+    #print('aclass', aclass)
+    if aclass != 1:
+      continue
+    attl = data[i:i+4]
+    i += 4
+    #print('TTL:', attl)
+    ardl = uint16(data[i:i+2])
+    i += 2
+    #print('Data len:', ardl, len(data)-i)
+    if len(data)-i < (ardl): #incomplete data
+      return None
+    
+    ardata = data[i: i+ardl]
+    
+    if atype == TYPE_A:
+      if ardl == 4:
+        ardata = data[i: i+ardl]
+        ip = '.'.join((str(x) for x in ardata))
+        #print('A:', {aname: ip})
+        adict['A'].append({aname: ip})
+    elif atype == TYPE_PTR or atype == TYPE_TXT:
+      ret = parseDNSstring(data[:i+ardl], i)
+      if ret:
+        ardata, j = ret
+        if atype == TYPE_PTR:
+          #print('PTR:', ardata)
+          adict['PTR'].append({aname: ardata})
+        elif atype == TYPE_TXT:
+          #print('TXT:', ardata)
+          adict['TXT'].append({aname: ardata})
+        else:
+          print('Other:', atype, data[i: i+ardl], ardata)
+    elif atype == TYPE_SRV:
+      ardata = data[i: i+ardl]
+      prio   = uint16(ardata[0:2])
+      weight = uint16(ardata[2:4])
+      port   = uint16(ardata[4:6])
+      ret = parseDNSstring(data[:i+ardl], i+6)
+      if ret:
+        target, j = ret
+        #print('SRV:', prio, weight, port, target)
+        adict['SRV'].append({aname: {'prio': prio, 'weight': weight, 'port': port, 'target': target}})
+    elif atype == TYPE_AAAA:
+      if ardl == 16:
+        ardata = data[i: i+ardl]
+        ip = ':'.join((hex(x) for x in ardata))
+        adict['AAAA'].append({aname: ip})
+        #print('AAAA:', {aname: ip})
+    else:
+      print('Other:', atype, data[i: i+ardl])
+    i += ardl
+    #print('ardata', ardata)
+    #if len(data)-i > 0:
+      #print("remaining Data:", data[i:])
+  
+  return adict
+
+def getUdps():
+  udps = usocket.socket(usocket.AF_INET, usocket.SOCK_DGRAM)
+  addr = usocket.getaddrinfo("0.0.0.0", 5353)[0][-1]
+  udps.bind(addr)
+  mreq = bytes([224, 0, 0, 251]) + bytes([0, 0, 0, 0])
+  udps.setsockopt(usocket.IPPROTO_IP, usocket.IP_ADD_MEMBERSHIP, mreq)
+  return udps
+
+def service2ip(services, service):
+  servers = []
+  for s in services:
+    for ptr in s['PTR']:
+      if service in ptr:
+        sname = ptr[service]
+        for srv in s['SRV']:
+          if sname in srv:
+            host = srv[sname]['target']
+            port = srv[sname]['port']
+            for a in s['A']:
+              if host in a:
+                servers.append((a[host], port))
+  return servers
+
+def test():
+  data = b'\x00\x00\x84\x00\x00\x00\x00\x06\x00\x00\x00\x00\x05_mqtt\x04_tcp\x05local\x00\x00\x0c\x00\x01\x00\x00\x11\x94\x00 \x1dMosquitto MQTT server on arc4\xc0\x0c\xc0(\x00\x10\x80\x01\x00\x00\x11\x94\x00\x01\x00\xc0(\x00!\x80\x01\x00\x00\x00x\x00\r\x00\x00\x00\x00\x07[\x04arc4\xc0\x17\xc0g\x00\x1c\x80\x01\x00\x00\x00x\x00\x10\xfd; \xc7u\x82\x00\x00\x8d\x99\x8e\xe8S\x91g\xc5\xc0g\x00\x1c\x80\x01\x00\x00\x00x\x00\x10\xfd; \xc7u\x82\x00\x00\x00\x00\x00\x00\x00\x00\x03\xd1\xc0g\x00\x01\x80\x01\x00\x00\x00x\x00\x04\xc0\xa8*~'
+  
+  services = parsePacket(data)
+  print('test:', service2ip([services,], b'_mqtt._tcp.local') == [('192.168.42.126', 1883)])
+
+def queryService(udps, service=b'_mqtt._tcp.local', timeout=1000):
+  try:
+    #udps.setblocking(True)
+    udps.sendto(makeServiceQuery(service), ('224.0.0.251', 5353))
+    #udps.setblocking(False)
+
+    services = []
+    
+    starttime = utime.ticks_ms()
+    while utime.ticks_diff(utime.ticks_ms(), starttime) < timeout:
+      poller = uselect.poll()
+      poller.register(udps, uselect.POLLIN)
+      while poller.poll(100):
+        try:
+          data, addr = udps.recvfrom(1024)
+          print(data, addr)
+          s = parsePacket(data)
+          if s:
+            services.append(s)
+        except OSError:
+          # No data to evaluate
+          pass
+  except Exception as e:
+    import sys
+    sys.print_exception(e)
+  
+  return service2ip(services, service)
+
+if __name__ == '__main__':
+  print("start test")
+  test()