EC200U-CN: SSL Handshake Failure (+QSSLOPEN: 0,579) / QMTOPEN 0,5 on Port 8883 — IoT SIM

Goku28 · August 6, 2026, 6:25am

Hello Quectel Support,

I am trying to connect an EC200U-CN module to a cloud MQTT broker (AWS IoT Core) using MQTT over TLS on port 8883, using X.509 mutual TLS authentication. The same module/firmware/certificate configuration connects successfully over a standard consumer SIM, but fails consistently when using an IoT-specific M2M SIM/APN.

Module / Network Details

Module : EC200U-CN
Firmware : EC200UCNAAR03A09M08
SIM : IoT/M2M SIM (carrier-provided APN)
TLS : X.509 mutual TLS (client cert + private key)

LTE / PDP Connection – Working

AT+CEREG?
+CEREG: 0,1
OK

AT+QIACT=1
OK

AT+QIACT?
+QIACT: 1,1,1,“10.x.x.x”
OK

DNS Resolution – Working

AT+QIDNSGIP=1,“.amazonaws.com”
OK
+QIURC: “dnsgip”,0,1,60
+QIURC: “dnsgip”,“”

Raw TCP Connectivity to Broker Port 8883 – Working

AT+QIOPEN=1,1,“TCP”,“.amazonaws.com”,8883,0,1
OK
+QIOPEN: 1,0

AT+QISTATE=1,1
+QISTATE: 1,“TCP”,“”,8883,0,2,1,1,1,“usbat”
OK

Therefore the broker endpoint and port 8883 are reachable from the modem over this SIM.

Certificate Files – Present in UFS

AT+QSSLCFG=“cacert”,2,“UFS:root-CA.crt”
AT+QSSLCFG=“clientcert”,2,“UFS:client.crt”
AT+QSSLCFG=“clientkey”,2,“UFS:client.key”
(all return OK)

TLS Configuration

AT+QSSLCFG=“seclevel”,2,2
AT+QSSLCFG=“sslversion”,2,3
AT+QSSLCFG=“ciphersuite”,2,0xC02F
AT+QSSLCFG=“ignorelocaltime”,2,1
AT+QSSLCFG=“sni”,2,1
(all return OK)

Direct TLS Test – Failing

AT+QSSLOPEN=1,2,0,“.amazonaws.com”,8883
OK
+QSSLOPEN: 0,579

AT+QIGETERROR
+QIGETERROR: 579,ssl handshake failed

MQTT Test – Consistent with TLS Failure

AT+QMTCFG=“ssl”,0,1,2
AT+QMTOPEN=0,“.amazonaws.com”,8883
OK
+QMTOPEN: 0,5

Cipher Suites Tested

0xFFFF (all supported ciphers)
0xC02F (ECDHE-RSA-AES128-GCM-SHA256)

Both result in the same:
+QSSLOPEN: 0,579
+QIGETERROR: 579,ssl handshake failed

Summary

LTE registration : PASS
PDP / IP : PASS
DNS : PASS
TCP to broker on 8883 : PASS
Certificate files in UFS : PASS
TLS handshake (QSSLOPEN) : FAIL - Error 579
MQTT open (QMTOPEN) : FAIL - Result 5

Key observation: identical module, firmware, and certificate configuration succeeds on a standard consumer SIM but fails only on the IoT/M2M SIM path, always at the TLS handshake stage rather than TCP or DNS.

Questions

Is there a known TLS/mTLS handshake compatibility issue on firmware EC200UCNAAR03A09M08, particularly with AWS IoT-style “-ats” endpoints?
Could differences in SIM/APN routing (e.g., MTU size, packet fragmentation handling) plausibly cause a TLS handshake to fail at error 579 while a plain TCP connection succeeds?
Is there a newer/recommended firmware build for EC200U-CN with improved AWS IoT Core TLS support? If so, could you provide the firmware package and QFlash upgrade procedure?
Is there any additional SSL/TLS debug logging available to identify the exact stage of handshake failure (e.g., ClientHello, Certificate exchange, Finished) beyond the generic error 579?

I can provide additional logs if needed.

Thank you.

herbert.pan-Q · August 6, 2026, 6:55am

pls refer to

Goku28 · August 6, 2026, 7:35am

Thank you for sharing the application manual. I followed it exactly, including the RAM:
certificate storage method shown in Section 3, but this is not supported on my module/firmware:

AT+QFLST=“RAM:*”
+CME ERROR: 400

Since RAM: storage is not usable on this firmware, I continued using UFS: storage
(as in my original test), with identical SSL/MQTT configuration to the manual’s Section 4-5.

I also re-verified endpoint reachability as suggested in the manual’s troubleshooting
section (step 4), which succeeds:

AT+QPING=1,“.amazonaws.com”
OK
+QPING: 0,“”,64,588,255
+QPING: 0,“”,64,320,255
+QPING: 0,“”,64,320,255
+QPING: 0,“”,64,320,255
+QPING: 0,4,4,0,320,588,353

However, the core issue reported in my earlier message remains unresolved. The TLS
handshake itself fails:

AT+QSSLOPEN=1,2,0,“.amazonaws.com”,8883
OK
+QSSLOPEN: 0,579

AT+QIGETERROR
+QIGETERROR: 579,ssl handshake failed

This confirms:

Network registration, PDP/IP: PASS
DNS resolution: PASS
ICMP reachability to endpoint (QPING): PASS
Raw TCP connect to endpoint on 8883: PASS
RAM: certificate storage: NOT SUPPORTED (+CME ERROR: 400) — worked around using UFS:
TLS handshake (QSSLOPEN): FAIL - Error 579
MQTT open (QMTOPEN): FAIL - Result 5

The failure is occurring specifically at the TLS handshake stage, before certificate
storage location (RAM vs UFS) or the MQTT layer come into play. The manual’s procedure does not resolve the
reported error.

Module: EC200U-CN
Firmware: EC200UCNAAR03A09M08

As previously requested: could you confirm whether this firmware has a known TLS
handshake compatibility issue with AWS IoT Core’s -ats endpoints?

Thank you.

herbert.pan-Q · August 6, 2026, 8:36am

I have sent the latest firmware to your email, pls check and try again

Goku28 · August 6, 2026, 11:22am

Hi,

I’m trying to flash the provided firmware (EC200UCNAAR03A17M08) using QFlash V8.0
but the download is failing at the handshake stage.

Setup:

Module: EC200U-CN, current firmware EC200UCNAAR03A09M08
Connected via USB, all standard Quectel ports enumerate correctly in normal mode
(AT Port COM14, Diag Port COM18, Modem COM16, etc.)
Firmware loaded correctly in QFlash (8915DM_cat1_EC200UCNAAR03A17M08.pac)

Issue:
When I select COM18 (Diag Port) or COM14 (AT Port) and click Start, QFlash attempts
to trigger download mode but times out:

“QDownload Fail (FAIL, Confirm dynamic com port 18 timeout(N)!)”

If I manually send AT+QDOWNLOAD=1 first, the module correctly switches and a new
port “SPRD U2S Diag (COM29)” appears in Device Manager — confirming the module
itself can enter download mode fine. But by the time I manually select COM29 in
QFlash and click Start, it gets stuck indefinitely at “DL Start” with no progress.

It seems to be a timing issue — the download-mode window closes before QFlash
can grab the port when done manually, and QFlash’s own auto-trigger via COM14/COM18
isn’t switching the module into download mode successfully either.

Could you advise:

Which COM port QFlash should target to auto-trigger download mode correctly
for this module?
Whether there’s a specific QFlash configuration (e.g. Firehose vs Sahara mode
under Configuration menu) required for this firmware package?
Any known timing/driver issue with QFlash V8.0 + EC200U-CN that causes this?
If my Qflash version is not support to my model provide me suitable version download file.

Thanks.