This is to return an error when a connection refused packet is returned from the remote host.
As `connect` is called in a non-blocking mode, things like refused connections don't get caught.
The subsequent `poll` will just block until the socket is ready, and as it's a file operator it doesn't know/care about refused network connections.
Therefore we need to add a check for socket errors after the poll, which should be enough to catch any connection errors.
ssl_server_cert - certificate for SSL server (rename from ssl_srvkey)
ssl_server_key - key for ssl_server_cert of generated mirm certificate (renamed from ssl_srvkey)
ssl_server_ca_file - CA file for mitm
ssl_server_ca_key - key for mitm CA
ssl_client_ca_file, ssl_client_ca_dir, ssl_client_ca_store - locations for root CAs used with ssl_client_verify for TLS client
ssl_certcache is not optional, if ssl_server_ca_file / ssl_server_ca_key are configured
ssl_client_ciphersuites - TLS client ciphers for TLS 1.3, e.g. ssl_client_ciphersuites TLS_AES_128_GCM_SHA256
ssl_server_ciphersuites - TLS server ciphers for TLS 1.3
ssl_client_cipher_list - TLS client ciphers for TLS 1.2 and below , e.g. ssl_client_cipher_list ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305
ssl_server_cipher_list - TLS server ciphers for TLS 1.2 and below
ssl_client_min_proto_version - TLS client min TLS version (e.g. TLSv1.2)
ssl_server_min_proto_version - TLS server min TLS version (e.g. TLSv1.2)
ssl_client_max_proto_version - TLS client max TLS version (e.g. TLSv1.2)
ssl_server_max_proto_version - TLS server max TLS version (e.g. TLSv1.2)
ssl_client_verify - verify certificate for upstream server in TLS client functionality
ssl_client_no_verify - do not verify certificate for upstream server in TLS client functionality (default)
