Hi @wdebbaut,
many thanks for the support, the replies that I have got from all of you have been very helpful so far! To answer your question:
Where do you see in your tcpdump -XX on the packet_forwarder that de dataLen is 0 ?
“dataLen” is a parameter declared within the LMIC struct, I just printed it out inside the arduino sketch, and this has allowed me to do a bit of debugging also on end-node side. As I said before, basically it gives you the number of bytes of the received payload. In my case always =0, indicating that I am not getting any packet at all.
Now I am wondering if the “txpk” I see in the log you posted is the actual JOIN_ACCEPT message to deliver to node, or just an acknowledgement, also considering what @arjanvanb said few posts ago:
the size of the acknowledgement might give you an indication if the gateway thinks all is fine? The NONE is 29 bytes, the TOO_LATE is 33 bytes.
In my case, the size of the sent packets is always 33 bytes, further confirming that the message is arriving too late. In order to make a fair comparison with the missing reception of downlink packets I am facing, would you be so kind to post the complete log you get running tcpdump command? Precisely, you might start from the uplink message (JOIN_REQUEST) sent from gateway to TTN, and then the downlink that follows.
I repost my log (OTAA not working) for your comprehension:
/* OTAA activation tentative. Device not activated! JOIN_ACCEPT message forwarded to endnode
5 seconds after JOIN_REQUEST */
11:04:50.435723 IP 31.157.192.137.49457 > 52.169.76.203.1700: UDP, length 243
0x0000: 4500 010f c9ec 4000 4011 0e57 1f9d c089 E.....@.@..W....
0x0010: 34a9 4ccb c131 06a4 00fb c605 01d9 6700 4.L..1........g.
0x0020: 0000 024b 0803 0571 7b22 7278 706b 223a ...K...q{"rxpk":
0x0030: 5b7b 2274 6d73 7422 3a39 3938 3937 3935 [{"tmst":9989795
0x0040: 3438 2c22 7469 6d65 223a 2232 3031 372d 48,"time":"2017-
0x0050: 3031 2d32 3754 3130 3a30 343a 3530 2e34 01-27T10:04:50.4
0x0060: 3335 3131 315a 222c 2263 6861 6e22 3a30 35111Z","chan":0
0x0070: 2c22 7266 6368 223a 312c 2266 7265 7122 ,"rfch":1,"freq"
0x0080: 3a38 3638 2e31 3030 3030 302c 2273 7461 :868.100000,"sta
0x0090: 7422 3a31 2c22 6d6f 6475 223a 224c 4f52 t":1,"modu":"LOR
0x00a0: 4122 2c22 6461 7472 223a 2253 4638 4257 A","datr":"SF8BW
0x00b0: 3132 3522 2c22 636f 6472 223a 2234 2f35 125","codr":"4/5
0x00c0: 222c 226c 736e 7222 3a31 312e 382c 2272 ","lsnr":11.8,"r
0x00d0: 7373 6922 3a2d 3335 2c22 7369 7a65 223a ssi":-35,"size":
0x00e0: 3233 2c22 6461 7461 223a 2241 4730 7a41 23,"data":"AG0zA
0x00f0: 5042 2b31 624e 774c 6439 376a 746d 5761 PB+1bNwLd97jtmWa
0x0100: 5144 675a 3552 3932 4e77 3d22 7d5d 7d QDgZ5R92Nw="}]}
11:04:51.254810 IP 52.169.76.203.1700 > 31.157.192.137.49457: UDP, length 4
0x0000: 4500 0020 b229 4000 2c11 3b09 34a9 4ccb E....)@.,.;.4.L.
0x0010: 1f9d c089 06a4 c131 000c 6d8b 01d9 6701 .......1..m...g.
11:04:55.914887 IP 52.169.76.203.1700 > 31.157.192.137.44731: UDP, length 198
0x0000: 4500 00e2 b68a 4000 2c11 35e6 34a9 4ccb E.....@.,.5.4.L.
0x0010: 1f9d c089 06a4 aebb 00ce a1a4 0100 0003 ................
0x0020: 7b22 7478 706b 223a 7b22 696d 6d65 223a {"txpk":{"imme":
0x0030: 6661 6c73 652c 2274 6d73 7422 3a31 3030 false,"tmst":100
0x0040: 3339 3739 3534 382c 2266 7265 7122 3a38 3979548,"freq":8
0x0050: 3638 2e31 2c22 7266 6368 223a 302c 2270 68.1,"rfch":0,"p
0x0060: 6f77 6522 3a31 342c 226d 6f64 7522 3a22 owe":14,"modu":"
0x0070: 4c4f 5241 222c 2264 6174 7222 3a22 5346 LORA","datr":"SF
0x0080: 3842 5731 3235 222c 2263 6f64 7222 3a22 8BW125","codr":"
0x0090: 342f 3522 2c22 6970 6f6c 223a 7472 7565 4/5","ipol":true
0x00a0: 2c22 7369 7a65 223a 3333 2c22 6461 7461 ,"size":33,"data
0x00b0: 223a 2249 4779 6469 494b 5073 6b77 3064 ":"IGydiIKPskw0d
0x00c0: 5230 7654 4234 686e 3463 4f48 6462 6b64 R0vTB4hn4cOHdbkd
0x00d0: 5967 622f 4458 6874 2f6c 4872 4f79 4222 Ygb/DXht/lHrOyB"
0x00e0: 7d7d }}
With regard to my log, I can definitely say:
-
“tmst_rxpk”=998979548 us / “tmst_txpk”=1003979548 us (difference = 5 sec, so TTN tell the gateway to send the downlink packet 5 sec after the received uplink)
-
“time_rxpk”=11:04:50.435723 / “time_txpk”=11:04:55.914887 (difference = 5.479164 sec, so the downlink message arrives later than the time scheduled by TTN for sending message back to end-node).