RE: Unexpected TCP connection resets on nRF9160

Stephan Walter — Tue, 17 Sep 2024 09:05:35 GMT

Thank you for your help. As said in the other comments, the RST packets cannot come from the server. We are now suspecting a middleware/firewall that issues these unexpected RST packets.

RE: Unexpected TCP connection resets on nRF9160

Hakon — Tue, 30 Jul 2024 13:22:18 GMT

Modem team;

Proper modem log with default trace set is needed for detailed study.

RE: Unexpected TCP connection resets on nRF9160

Stephan Walter — Mon, 29 Jul 2024 06:13:44 GMT

Hi, the ~5 seconds interval between SYN/ACK and POLLERR is true on the client. But on the server, the RST is sent 21 seconds after the handshake. The POLLERR can therefore not be triggered by the RST packet.

RE: Unexpected TCP connection resets on nRF9160

Hakon — Fri, 26 Jul 2024 10:37:45 GMT

Modem team;

Modem trace was taken in such a limited set that it doesn’t help here. Anyway, as customer has analyzed TCP packets are lost during TCP handshake. Due not receiving ACK to SYN ACK server sends TCP RST which causes modem to send Socket closed notification to application. This is causing the error NRF_ECONNRESET. The ~5sec delay between modem data transmission and POLLERR nicely matches to attached picture, where modem TCP traffic is presented. Everything is working as expected.

[09:00:02,170] INFO - [00:00:03.568,359] <inf> srv_lte: Transition to ON
[09:00:02,464] INFO - [00:00:03.608,032] <inf> srv_lte: State ON
[09:00:02,464] INFO - [00:00:03.680,389] <inf> srv_lte: C:RMOD0 H:0 Wait for registration
[09:00:04,382] INFO - [00:00:05.790,924] <inf> srv_lte: PLMN=22801 ECI=1060502 EARFCN=6300 RSRP=-88dBm RSRQ=-7.5dB SNR=16dB
[09:00:04,616] INFO - [00:00:05.868,072] <inf> srv_lte: C:RMOD0 H:0 Resolve 159.168.140.122:10040
[09:00:04,617] INFO - [00:00:05.871,704] <inf> srv_lte: C:RMOD0 H:0 S:0 Connecting to 159.168.140.122:10040
[09:00:04,617] INFO - [00:00:05.929,199] <inf> srv_lte: C:RMOD0 H:0 S:0 Connected
[09:00:04,617] INFO - [00:00:05.931,152] <inf> srv_lte: C:RMOD0 H:0 S:0 RX thread start
[09:00:04,617] INFO - [00:00:05.931,396] <inf> srv_lte: C:RMOD0 H:0 S:0 Sending 61 byte(s)
[09:00:09,421] INFO - [00:00:10.660,736] <wrn> srv_lte: C:RMOD0 H:0 S:0 POLLERR
[09:00:09,421] INFO - [00:00:10.662,506] <inf> srv_lte: C:RMOD0 H:0 S:0 SO_ERROR=104
[09:00:09,421] INFO - [00:00:10.764,099] <inf> srv_lte: Transition to OFF
[09:00:09,421] INFO - [00:00:10.766,113] <inf> srv_lte: C:RMOD0 H:0 S:0 RX thread end
[09:00:11,203] INFO - [00:00:12.395,233] <inf> srv_lte: State OFF

RE: Unexpected TCP connection resets on nRF9160

Hakon — Thu, 25 Jul 2024 11:00:35 GMT

Hello,

I have reported this to the modem team.