Dropped frames between XBee Series 2 and ConnectPort X2

I am experiencing dropped frames at the beginning of transmission between an XB24-B module + XBIB USB dev board combo and a ConnectPort X2. The XB24-B is running ZNET 2.5 Router/End Device AT firmware with default params. The X2 is running Firmware 2.6.4 (Version 82001596_A 09/27/2007). Here is the procedure I use to replicate the problem.

STEP 1: Upload the following python program to the X2


include the sockets module into the namespace:

from socket import *
import sys

Create the socket, datagram mode, proprietary transport:


Bind to endpoint 0xe8 (234):

sd.bind((“”, 0xe8, 0, 0))

while 1:

# Block until a single frame is received, up to 72 bytes:
payload, src_addr = sd.recvfrom(72)

print "src_addr: ", src_addr

print "len(payload): %d" % len(payload)
for index, byte in enumerate(payload):
    print "payload[%d] = '%s' (%s, %d)" % (index, byte, hex(ord(byte)), ord(byte))
    if byte == 'z':


STEP 2: Reboot the X2 and do a network discovery via the web interface. In the web interface, both the coordinator and the router (modem) appear.

STEP 3: Start X-CTU, test/query the modem, and go to the terminal interface.

STEP 4: Telnet to the X2 and start the above python program (#1 in the attached screen capture).

STEP 5: In the X-CTU terminal window, starting typing the alphabet slowly (#2 in the screen capture).

STEP 6: Notice in the telnet session that characters ‘a’, ‘b’ and ‘c’ didn’t arrive (#3 in the screen capture). This is verified by looking at the mesh network counters in the web interface (#4 in the screen capture).

So the obvious question then, why don’t the first few frames go through? Shouldn’t this scare the hell out of me? :wink: As always, any help is much appreciated.


We have not observed a dropped datagram behavior such as the one you have described but I have a suspicion as to what is going on.

On the XBee module which is attached to your X-CTU session, could you please tell me the following:

  1. If you are using the AT mode router firmware what are the values of DH and DL?

  2. If you are using the API mode router firmware what are the address parameters you are using to transmit?

If the destination address is 00:00:00:00:00:00:ff:ff! (DH=00000000/DL=0000FFFF) this will transmit each and every packet from the XBee module as a broadcast packet.

Broadcast data is unreliable and unacknowledged so that may explain the behavior you are seeing.

If this isn’t the case, let us know and we’ll definitely figure out what is going on!

Great advice. I’m new to xbees and am getting better, and I thought others might like a walkthrough for a fix. In case anyone else has this problem check this out: t413.com/news/fast-2-way-xbee-series-2-data