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ais_capture.py
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ais_capture.py
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import socket
import ais
from ais import DecodeError
import logging
import json
import sys
from process_ais import Ais_Processor
import traceback
aisprocessor = Ais_Processor()
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(levelname)s - %(message)s')
UDP_IP_ADDRESS = "127.0.0.1"
UDP_PORT_NO = 10110
def connect():
serverSock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
serverSock.bind((UDP_IP_ADDRESS, UDP_PORT_NO))
print("Connected to AIS server")
return serverSock
serverSock = connect()
print "AIS listener started"
session = {}
def getmessage():
global serverSock
data, addr = serverSock.recvfrom(1024)
payload = data.split(",")
pad = int(payload[-1].split('*')[0][-1])
msglength = int(payload[1])
msgpart = int(payload[2])
msgseqid = 0
if payload[3]:
msgseqid = int(payload[3])
msg = payload[5]
return (msg, pad, msgpart, msglength, msgseqid)
while True:
try:
msg, pad, msgpart, msglength, msgseqid = getmessage()
if msglength == 1:
decodedmessage = ais.decode(msg,pad)
aisprocessor.process(decodedmessage)
else:
while msglength != msgpart:
msgfragment, pad, msgpart, msglength, msgseqid = getmessage()
msg += msgfragment
if msglength == msgpart: # Is this the final part?
decodedmessage = ais.decode(msg[0:71], 2) # libais rejects AIS5 messages where pad is NOT 2 and length is NOT 71
aisprocessor.process_ais5(decodedmessage)
except DecodeError:
pass
except:
logging.error(traceback.format_exc())