DCMTK

DCMTK 3.6.2 does not accept network connections with TLS 1.2 when compiled with OpenSSL < 1.1.0
The reason is that for older versions of OpenSSL, the following methods are called, which explicitly only support TLS 1.0:

• TLSv1_server_method(), TLSv1_client_method(), TLSv1_method()

So neither TLS 1.1 nor TLS 1.2 can be negotiated in this case. For older OpenSSL versions, preferrably the following methods should be used:

• SSLv23_server_method(), SSLv23_client_method(), SSLv23_method()

In order to avoid the insecure SSLv2 and SSLv3 protocols, only TLS cipher suites should be enabled using setCipherSuites().
Additionally, SSL_CTX_set_min_proto_version() should be called to set the minimum protocol to TLS1_VERSION.