Osmocom's Base Station Controller for 2G mobile networks https://osmocom.org/projects/osmobsc
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osmo-bsc/contrib/nat/ussd_example.py

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#!/usr/bin/env python2.7
"""
AGPLv3+ 2016 Copyright Holger Hans Peter Freyther
Example of how to connect to the USSD side-channel and how to respond
with a fixed message.
"""
import socket
import struct
ussdSocket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
ussdSocket.connect(('127.0.0.1', 5001))
def send_dt1(dstref, data):
dlen = struct.pack('B', len(data)).encode('hex')
hex = '06' + dstref.encode('hex') + '00' + '01' + dlen + data.encode('hex')
pdata = hex.decode('hex')
out = struct.pack('>HB', len(pdata), 0xfd) + pdata
ussdSocket.send(out)
def send_rel(srcref, dstref):
hex = '04' + dstref.encode('hex') + srcref.encode('hex') + '000100'
pdata = hex.decode('hex')
out = struct.pack('>HB', len(pdata), 0xfd) + pdata
ussdSocket.send(out)
def recv_one():
plen = ussdSocket.recv(3)
(plen,ptype) = struct.unpack(">HB", plen)
data = ussdSocket.recv(plen)
return ptype, data
# Assume this is the ID request
data = ussdSocket.recv(4)
ussdSocket.send("\x00\x08\xfe\x05\x00" + "\x05\x01" + "ussd")
# ^len ^len of tag ... and ignore
# Expect a fake message. see struct ipac_msgt_sccp_state
ptype, data = recv_one()
print("%d %s" % (ptype, data.encode('hex')))
(srcref, dstref, transid, invokeid) = struct.unpack("<3s3sBB", data[1:9])
print("New transID %d invoke %d" % (transid, invokeid))
# Expect a the invocation.. todo.. extract invoke id
ptype, data = recv_one()
print("%d %s" % (ptype, data.encode('hex')))
# Reply with BSSAP + GSM 04.08 + MAP portion
# 00 == invoke id 0f == DCS
res = "01002a9b2a0802e1901c22a220020100301b02013b301604010f041155e7d2f9bc3a41412894991c06a9c9a713"
send_dt1(dstref, res.decode('hex'))
clear = "000420040109"
send_dt1(dstref, clear.decode('hex'))
# should be the clear complete
send_rel(srcref, dstref)
# Give it some time to handle connection shutdown properly
print("Gracefully sleeping")
import time
time.sleep(3)