Unable to establish connection

[AlanMaxwell]

Hello.
I tried to use performed example on Ubuntu and Mac OS, but every time I get the same error:

======> Connecting to gateway.sandbox.push.apple.com:2195...
======> Resolving server hostname...
======> Creating socket...
======> Socket successfully created
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation now in progress (errno: 36)
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation already in progress (errno: 37)
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation already in progress (errno: 37)
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation already in progress (errno: 37)
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation already in progress (errno: 37)
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation already in progress (errno: 37)
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation already in progress (errno: 37)
======> Trying to connect to x.x.x.x...
======> Could not to connect to: Operation already in progress (errno: 37)
======> Unable to establish connection
======> Connection closing...
======> Connection closed
Could not connect to Apple Push Notification Service: unable to establish connection (errno: 9013)

Instead of x.x.x.x are various IPs.

I tried two ways:
-p12 file
-cert and key .pem files

Tried to use apn-pusher and got the same result.

I tested certificates with the other push-messaging applications and they are working.

What should I do to make it work?

[bouzikas]

Same here. Any workaround?

[AlanMaxwell]

Same here. Any workaround?

Yes. I just decided to use other libraries.
Now to send a push notification I send http request via "boost asio" functionality to Firebase service. That for "background push" and "push notification".
For sending a VoIP push I configured nghttp2 library and send http2 requests.

[bouzikas]

Funny thing but I found where the problem is. For some reason, if you comment out lines 607 & 608 (610 & 611 for windows) in apn.c:
int sock_flags = fcntl(ctx->sock, F_GETFL, 0);
fcntl(ctx->sock, F_SETFL, sock_flags | O_NONBLOCK);
you got the connection right but there is another issue still (unrelated to flags).

======> Connecting to api.sandbox.push.apple.com:2197...
======> Resolving server hostname...
======> Creating socket...
======> Socket successfully created
======> Trying to connect to x.x.x.x...
======> Connection has been established
======> Initializing SSL connection...
======> Certificate subject: UID=com.XXXXXXXXX, CN=Apple Push Services: com.XXXXXX, OU=XXXXXX, O=XXXXXX., C=US
======> Certificate issuer: C=US, O=Apple Inc., OU=Apple Worldwide Developer Relations, CN=Apple Worldwide Developer Relations Certification Authority
======> Certificate mode: PRODUCTION & SANDBOX (UNIVERSAL) (6)
======> Certificate expires at 2021-08-06 16:04:12
======> ssl: handshake started write:before SSL initialization:unknown
======> ssl: connect:before SSL initialization:(NONE)
======> ssl: connect:SSLv3/TLS write client hello:(NONE)
======> ssl: alert read:SSLv3/TLS write client hello
======> ssl: connect:error
======> Could not initialize SSL connection: SSL_connect() failed: error:00000001:lib(0):func(0):reason(1), Undefined error: 0 (errno: 0):

Is anyone has the same issue?