FRMR frame reason

btw, as DeepSeek says it's a Gurux DLMS Director bug, here is a quote
"
Based on a detailed analysis of the search results, particularly the Gurux forum posts, I can identify the likely software error in GXDLMSDirector that causes it to mishandle timeouts and subsequently trigger FRMR responses from the meter.

The Identified Error: Premature "Disconnect Mode" State
The core problem appears to be that after a timeout occurs, the GXDLMSDirector enters an internal "Disconnect mode" but still attempts to send new data frames. This creates a desynchronization where the client (PC) believes the connection is disconnected, but the meter is still waiting for properly sequenced frames.

Evidence from the Logs
The logs you provided show the exact pattern that other users have reported.
The Root Cause: Incorrect State Management
Based on the search results and the code references in the exception stack traces, I have identified the likely bug location:

After Timeout, Library Enters "Disconnect Mode": When ReadDLMSPacket() times out, the GXDLMS library marks the connection as disconnected internally . This is a defensive mechanism to prevent further communication on a broken link.

Bug: "Disconnect" Flag Not Properly Reset: The core error is that after entering this disconnect mode, the internal flag is not correctly cleared when new data arrives from the meter . The meter might still be active and ready to communicate (as shown by your log at 16:58:47), but the client software is stuck in a disconnected state.

Resulting FRMR: Because the client software is in a "disconnected" state, it bypasses the normal HDLC sequence number management (N(S)/N(R) counters) when it sends the next I-frame. The meter, still in a connected state, receives this frame, detects the invalid sequence number, and correctly responds with a FRMR (Frame Reject)
"

More to say. DeepSeek gives me as much as 3 code modifications to try.
Third of them works much better, though not ideal ( successfull data transfer probability after timeout is not 100% but much bigger than 0% of original source)

Hello Mikko.

here are some more logs.

Log1 (frame delay =0 )

original Gurux src
Typical FRMR just after data send failed

15:39:27 Reading object 0.0.44.0.0.255, interface ImageTransfer
TX: 7E A0 1A 02 23 61 54 A0 32 E6 E6 00 C0 01 C1 00 12 00 00 2C 00 00 FF 05 00 73 FC 7E
15:39:29
RX: 7E A0 13 61 02 23 74 DE D2 E6 E7 00 C4 01 C1 00 03 01 B3 FA 7E
15:39:29 Reading object 0.0.44.0.0.255, interface ImageTransfer
TX: 7E A0 1A 02 23 61 76 B0 30 E6 E6 00 C0 01 C1 00 12 00 00 2C 00 00 FF 02 00 7B B1 7E
15:39:34 Data send failed. Try to resend 1/3
15:39:39 Data send failed. Try to resend 2/3
15:39:41
RX: 7E A0 16 61 02 23 96 96 30 E6 E7 00 C4 01 C1 00 06 00 00 01 00 A5 01 7E
15:39:41 Reading object 0.0.44.0.0.255, interface ImageTransfer
TX: 7E A0 1A 02 23 61 98 C0 3E E6 E6 00 C0 01 C1 00 12 00 00 2C 00 00 FF 03 00 A3 A8 7E
15:39:42
RX: 7E A0 08 61 02 23 97 E7 F4 7E

Log2 (frame delay =200 )

original Gurux src
Typical FRMR just after data send failed

15:58:11 Updating image update...
TX: 7E A8 8A 02 23 61 F6 F5 AB E6 E6 00 C3 01 C1 00 12 00 00 2C 00 00 FF 02 01 02 02 06 00 00 00 4A 09 82 01 00 D7 40 D9 8F A3 00 F4 00 23 12 94 00 F2 40 62 44 D2 44 42 49 B2 49 22 4A 05 61 82 80 39 71 52 D4 06 DE 22 DC 26 DA 4A D8 4E D6 56 D2 5A D0 03 47 15 00 93 06 F0 0F 83 57 65 00 2A 8A 63 05 D7 04 83 56 45 00 9D 8A 33 17 D7 00 93 16 87 01 E1 86 13 77 F7 0F 63 DF 06 00 06 07 93 16 87 01 85 07 C2 07 E1 86 C1 A2 B4 7E
15:58:12
RX: 7E A0 08 61 02 23 91 D1 91 7E
15:58:12 Updating image update...
TX: 7E A8 8A 02 23 61 F8 8B 42 83 13 77 F7 0F E3 C7 06 FE 23 13 FA 00 F2 50 62 54 D2 54 42 59 B2 59 22 5A 92 5A 02 5B 21 61 82 80 03 57 25 00 8D 83 13 84 17 00 13 7B 77 00 33 3B 60 01 0D 83 3A 9B 13 89 85 00 93 09 00 02 93 0A F0 0F E3 75 64 FD B3 07 8B 40 63 F4 F9 00 93 07 00 02 13 96 07 01 41 82 8A 85 33 05 24 01 93 F4 F7 0F BD 2B 63 0B 8B 02 93 87 F4 FF 93 F7 F7 0F 13 06 14 00 3E 96 42 06 8A 87 41 82 31 A0 13 91 B2 7E
15:58:12
RX: 7E A0 08 61 02 23 B1 D3 B0 7E
15:58:12 Updating image update...
TX: 7E A0 25 02 23 61 FA F9 C0 94 06 01 41 80 63 00 C4 02 03 C7 07 00 93 06 14 00 85 07 E3 06 57 FF 63 1C 8B 00 7E 47 7E
15:58:17 Data send failed. Try to resend 1/10
15:58:21
RX: 7E A0 12 61 02 23 DE CA D3 E6 E7 00 C7 01 C1 00 00 FC B4 7E
15:58:21 Updating image update...
TX: 7E A8 8A 02 23 61 1C A1 E3 E6 E6 00 C3 01 C1 00 12 00 00 2C 00 00 FF 02 01 02 02 06 00 00 00 4B 09 82 01 00 83 57 2A 00 23 13 FA 00 AD B7 E3 0B 8B FE E3 6F 64 F9 85 B7 0E 04 42 04 41 80 93 17 87 01 23 13 8A 00 E1 87 E3 D7 07 F4 06 07 93 17 87 01 05 04 42 04 E1 87 41 80 13 77 F7 0F E3 C7 07 FE 23 13 8A 00 05 BF 79 71 26 D2 93 14 37 00 B3 87 E4 40 56 CA 8A 07 93 8A 01 18 D6 97 52 CC 03 AA 87 01 5E C6 AE 8B CC C1 B8 7E
15:58:21
RX: 7E A0 08 61 02 23 97 E7 F4 7E

LOG2 (frame delay=0)

src after deep seek modification applied

RX: 7E A0 08 61 02 23 31 DB 34 7E
16:08:16 Updating image update...
TX: 7E A0 25 02 23 61 72 B9 C8 45 EF A0 A3 51 EF E0 93 00 B2 40 05 45 41 01 82 80 41 11 85 45 37 05 00 10 06 C6 8D 8C 7E
16:08:17
RX: 7E A0 12 61 02 23 56 8A DB E6 E7 00 C7 01 C1 00 00 FC B4 7E
16:08:17 Updating image update...
TX: 7E A8 8A 02 23 61 94 E1 EB E6 E6 00 C3 01 C1 00 12 00 00 2C 00 00 FF 02 01 02 02 06 00 00 00 27 09 82 01 00 EF 80 A3 5E B7 77 00 40 98 47 79 9B 98 C7 98 47 13 67 07 20 98 C7 98 47 13 67 07 40 98 C7 EF A0 03 75 B2 40 41 01 6F E0 93 62 41 11 26 C2 06 C6 22 C4 89 47 AE 84 63 08 F5 04 63 E9 A7 02 1D CD EF A0 C3 6F 2A 84 15 C4 97 F7 FF FF 93 87 47 2F 23 20 F4 16 26 85 EF C0 40 27 23 24 A4 10 22 85 22 44 B2 40 92 73 05 7E
16:08:22 Data send failed. Try to resend 1/10
16:08:24 Recovery: HDLC state reset after timeout - received valid data. 7E A0 08 61 02 23 71 DF 76 7E
16:08:24
RX: 7E A0 08 61 02 23 71 DF 76 7E
16:08:24 Updating image update...
TX: 7E A8 8A 02 23 61 96 F3 C8 44 41 01 6F C0 73 4F 8D 47 E3 09 F5 FC B2 40 22 44 92 44 41 01 82 80 EF A0 A3 6C 2A 84 79 F0 FD B7 EF A0 A3 6C 2A 84 55 FC D5 B7 41 11 22 C4 26 C2 06 C6 89 47 2E 84 B2 84 63 09 F5 02 63 EF A7 00 29 C1 EF A0 43 69 26 86 A2 85 81 46 EF C0 53 7C B2 40 22 44 92 44 41 01 82 80 8D 47 E3 03 F5 FE B2 40 22 44 92 44 41 01 82 80 EF A0 03 68 26 86 A2 85 81 46 EF C0 D3 79 B2 40 22 44 92 44 41 21 89 7E
16:08:24
RX: 7E A0 08 61 02 23 71 DF 76 7E
16:08:24 Updating image update...
TX: 7E A0 25 02 23 61 98 ED 80 01 82 80 EF A0 E3 65 26 86 A2 85 81 46 EF C0 53 78 B2 40 22 44 92 44 41 01 82 80 E5 04 7E
16:08:29 Data send failed. Try to resend 1/10
16:08:34 Data send failed. Try to resend 2/10
16:08:39 Data send failed. Try to resend 3/10
16:08:41 Recovery: HDLC state reset after timeout - received valid data. 7E A0 08 61 02 23 91 D1 91 7E
16:08:41
RX: 7E A0 08 61 02 23 91 D1 91 7E
16:08:41 Updating image update...
TX: 7E A8 8A 02 23 61 BA 9D 23 E6 E6 00 C3 01 C1 00 12 00 00 2C 00 00 FF 02 01 02 02 06 00 00 00 28 09 82 01 00 01 11 97 07 00 00 93 87 87 F2 3E C4 28 00 97 07 00 00 93 87 27 F8 06 CE 3E C6 EF B0 F0 75 EF A0 61 44 EF A0 91 6B EF 70 92 61 F2 40 05 61 82 80 41 11 06 C6 EF A0 A3 64 B2 40 41 01 6F F0 E3 53 41 11 06 C6 EF A0 A3 63 B2 40 41 01 6F F0 83 5E 13 87 01 0D 83 46 C7 00 08 CB FD 57 99 E6 83 57 67 01 E2 07 FD 21 0A 7E
16:08:41
RX: 7E A0 08 61 02 23 B1 D3 B0 7E
16:08:41 Updating image update...
TX: 7E A8 8A 02 23 61 BC AB 46 87 93 E7 17 00 9C C1 13 C5 16 00 82 80 03 D6 01 FF 95 45 2D 45 6F B0 C1 0D 03 D6 C1 FB 95 45 29 45 6F B0 01 0D 03 D6 C1 EE 95 45 25 45 6F B0 41 0C 03 D6 81 F8 95 45 21 45 6F B0 81 0B 03 D6 81 EB 95 45 1D 45 6F B0 C1 0A 69 C1 41 11 22 C4 26 C2 06 C6 4A C0 83 97 41 0D 2A 84 93 84 01 0D B5 E3 83 C7 14 00 81 C7 FD 17 A3 80 F4 00 22 85 EF 40 93 30 2E 87 93 07 80 3E 13 06 80 3E 81 46 7F 3E A5 7E
16:08:41
RX: 7E A0 08 61 02 23 B1 D3 B0 7E
16:08:41 Updating image update...
TX: 7E A0 25 02 23 61 BE D9 C4 95 A7 F0 FF 95 E7 C4 EF 10 94 11 83 D7 64 00 13 07 30 1F AA 97 C2 07 C1 83 63 6A 87 BF 7E
16:08:41
RX: 7E A0 08 61 02 23 B1 D3 B0 7E
16:08:41 Updating image update...
TX: 7E A8 8A 02 23 61 D0 C1 EF E6 E6 00 C3 01 C1 00 12 00 00 2C 00 00 FF 02 01 02 02 06 00 00 00 29 09 82 01 00 F7 00 B2 40 22 44 23 93 F4 00 02 49 92 44 41 01 82 80 B2 40 22 44 23 9B 01 0C 85 47 23 84 F4 00 02 49 92 44 41 01 82 80 EF 40 53 2B 83 D7 44 00 89 8F C2 07 C1 87 23 92 F4 00 83 D7 44 00 C2 07 C1 87 E3 42 F0 F8 13 89 41 16 03 25 49 00 EF B0 A3 0B 03 25 89 00 EF B0 23 0B 01 47 01 46 81 46 81 45 03 A5 01 96 73 7E
16:08:42
RX: 7E A0 08 61 02 23 97 E7 F4 7E

In short, original src never outlast ping timeout.
deep seek src modification, in general, may outlast one or two ping timeouts.
Frame delay = 200 gives no help in my case.

Best regards, Andre

Hello Mikko,

I'm using tcp/ip over gsm 900/1800 MHz, typical ping time (RTT) varies from 400 ms to 3s, sometimes packet loss occured.

Now I'm playing with 'Wait time' parameter in connection settings.
According to SIMCOM modem manual:

"
1. Send the TCP packet, here as a sample, the module measures
<ESTIMATED_ROUND_TRIP_TIME> as 3 seconds. In runtime, each retransmission would
use the latest measured <ESTIMATED_ROUND_TRIP_TIME> value in the following steps.
2. Wait 3 seconds, and if TCP ACK packet is not got, resend the packet
3. Wait another 6 seconds, and if TCP ACK packet is not got, resend the packet
4. Wait another 12 seconds, and if TCP ACK packet is not got, resend the packet
5. Wait another 24 seconds, and if TCP ACK packet is not got, resend the packet
6. Wait another 48 seconds, and if TCP ACK packet is not got, resend the packet
7. Wait another 27 seconds, and if TCP ACK packet is not got, regard it as socket sending failure
and close the socket. (Here only 27 seconds is waiting because that the total trying time is 2
minutes).
8. If the TCP ACK packet is got within the previous steps, the packet is regarded as sent
successfully.
"

Looks to me if my max RTL is about 3s and 'Wait time' is 5 seconds, DLMS Director will resend data request even before modem TCP data retransmit timer occur, so here is a place where a glitch might happen.

So now I'm trying to increase 'Wait time' to a bigger values to see if this will help.

Best regards, Andre