From 46a0e6583effc9c6d99d6dbfd76527aa6c81d25b Mon Sep 17 00:00:00 2001
From: Mark Jessop <vk5qi@rfhead.net>
Date: Tue, 29 Jan 2019 22:41:47 +1030
Subject: [PATCH] Added wenet link emulation script.

---
 tx/examples/wenet_link_emulation.py | 146 ++++++++++++++++++++++++++++
 1 file changed, 146 insertions(+)
 create mode 100644 tx/examples/wenet_link_emulation.py

diff --git a/tx/examples/wenet_link_emulation.py b/tx/examples/wenet_link_emulation.py
new file mode 100644
index 0000000..7f55256
--- /dev/null
+++ b/tx/examples/wenet_link_emulation.py
@@ -0,0 +1,146 @@
+#!/usr/bin/env python
+#
+#   Emulate the function of a wenet downlink system, to enable testing of the secondary
+#   packet functionality.
+#   
+#   Note that these scripts ONLY work in Python 2 at the moment (sorry...)
+#
+#   To use this, start this script in a terminal window with:
+#   $ python wenet_link_emulation.py
+#
+#   You may then start up the secondary payload tx example script in another terminal with:
+#   $ python sec_payload_tx_example.py
+#   which will start emitting example text and floating point packets.
+#
+#   In yet another terminal, navigate to the wenet/rx/ directory and run:
+#   $ python sec_payload_rx_example.py
+#
+#   The 'received' secondary payload packets will be displayed as if they were received via a wenet link.
+#
+#   Copyright (C) 2019  Mark Jessop <vk5qi@rfhead.net>
+#   Released under GNU GPL v3 or later
+#
+
+import json
+import socket
+import struct
+import datetime
+import traceback
+
+WENET_SECONDARY_UDP_PORT = 55674
+WENET_TELEMETRY_UDP_PORT = 55672
+
+
+# Telemetry packets are send via UDP broadcast in case there is other software on the local
+# network that wants them.
+def broadcast_telemetry_packet(data):
+    telemetry_socket = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
+    # Set up the telemetry socket so it can be re-used.
+    telemetry_socket.setsockopt(socket.SOL_SOCKET,socket.SO_BROADCAST,1)
+    telemetry_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+
+    # We need the following if running on OSX.
+    try:
+        telemetry_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+    except:
+        pass
+
+    # Place data into dictionary.
+    data = {'type': 'WENET', 'packet': list(bytearray(data))}
+
+    # Send to broadcast if we can.
+    try:
+        telemetry_socket.sendto(json.dumps(data), ('<broadcast>', WENET_TELEMETRY_UDP_PORT))
+    except socket.error:
+        telemetry_socket.sendto(json.dumps(data), ('127.0.0.1', WENET_TELEMETRY_UDP_PORT))
+
+    telemetry_socket.close()
+
+
+def generate_secondary_payload_packet(id=1, data=[], repeats=1):
+    """ Generate  packet supplied by a 'secondary' payload.
+    These will usually be provided via a UDP messaging system, described in the functions
+    further below.
+
+    Keyword Arguments:
+    id (int): A payload ID number, 0-255.
+    data (list): The payload contents, as a list of integers. Maximum of 254 bytes.
+    repeats (int): (Optional) The number of times to transmit this packet.
+    """
+
+    # Clip the id to 0-255.
+    _id = int(id) % 256
+
+    # Convert the provided data to a string
+    _data = str(bytearray(data))
+    # Clip to 254 bytes.
+    if len(_data) > 254:
+        _data = _data[:254]
+
+    
+    _packet = "\x03" + struct.pack(">B",_id) + _data
+
+    return _packet
+
+
+def process_udp(udp_packet):
+    """ Process received UDP packets. """
+
+    # Parse JSON
+    packet_dict = json.loads(udp_packet)
+
+    # There may be other UDP traffic on this port, so we filter for just 'WENET'
+    # telemetry packets.
+    if packet_dict['type'] == 'WENET_TX_SEC_PAYLOAD':
+        # Extract packet and secondary payload ID number.
+        packet = packet_dict['packet']
+        _id = packet_dict['id']
+
+        # Generate a 'secondary payload' packet, as would be transmitted.
+        _packet_blob = generate_secondary_payload_packet(id=_id, data=packet)
+
+        # Broadcast it via UDP.
+        broadcast_telemetry_packet(_packet_blob)
+
+        print("Repeated packet from ID: %d" % (_id))
+
+
+def udp_rx_thread():
+    """ Listen on a port for UDP broadcast packets, and pass them onto process_udp()"""
+    global udp_listener_running
+    s = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
+    s.settimeout(1)
+    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    try:
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+    except:
+        pass
+
+    s.bind(('',WENET_SECONDARY_UDP_PORT))
+    print("Started UDP Listener")
+    while True:
+        try:
+            m = s.recvfrom(2048)
+        except socket.timeout:
+            m = None
+        
+        if m != None:
+            try:
+                process_udp(m[0])
+            except:
+                traceback.print_exc()
+                pass
+    
+    print("Closing UDP Listener")
+    s.close()
+
+
+if __name__ == "__main__":
+    try:
+        # Start listening for UDP packets
+        udp_rx_thread()
+
+    # Keep on going until we get Ctrl-C'd
+    except KeyboardInterrupt:
+        # Stop the UDP listener.
+        udp_listener_running = False
\ No newline at end of file