> I don't understand how to write the callback functions some of > the OpenSSL ALPN functions expect, and the manual really isn't > helping there either, so I'd like some help. Use SSL_CTX_set_client_hello_cb to set a SSL_client_hello_cb_fn function, which you can parse to get TLSEXT_TYPE_server_name and TLSEXT_TYPE_application_layer_protocol_negotiation, and everything else sent in the Client Hello (if you need it) like SSL versions and ciphers supported. Within this callback you can change SSL_CTX depending on SNI and ALPN. Ignore the SNI and ALPN callbacks. client_hello_cb was only added in 1.1.1 so is often missing from old examples, FAQs and manuals. Angus
