[quote='803127021, development, /thread/803127, /profile/development'] Added the NSAppTransportSecurity key to the Info.plist file [/quote] Just FYI, ATS only applies to high-level APIs, so URLSession and things layered on top of it. It’s irrelevant to folks using lower-level APIs, like Network framework and BSD Sockets. Still, it doesn’t hurt to turn it off temporarily during testing (-: [quote='803127021, development, /thread/803127, /profile/development'] These are the prints made during the procedure. [/quote] My best guess here is that the remote peer is closing the connection immediately on receiving the Client Hello message. I’ve seen problems like that in the past, where a TLS implementation sees a newer version of the protocol, or a new TLS extension, and fails to handle it properly [1]. I recommend that you use a use a packet trace to see what’s happening on the ‘wire’. If my theory is connect, you’ll see: The SYN / SYN-ACK / ACK handshake, setting up the TCP connection. The TLS ClientHello coming f