ESP32 Forum

Hi,
The HTTPS connection is refused with the above error code. The connection was working fine and was able post some request to the said server, but after adding some mqtt bits (no relation to https), I'm getting the following error as shown in image. As you can see, the certificate is verified but the connection is refused. Please advise on this matter.

If anyone is facing the same issue, here are some insights to overcome this.
1. Go to SSL Labs Server Test online and check all the cipher-suites that is supported by the server.
2. you can either disable the hardware MPI (bignum) acceleration in the menuconfig or move some ISR to a different core, either option works as expected.
3. depending on the cipher-suites of the server, enable the same in the menuconfig under TLS key exchange methods.
Hope this helps.

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