javax.net.ssl.SSLException: Received fatal alert: unexpected_message

If you are attempting to establish an SSL Connection as a client to a server and getting this error at the very end of the SSL Handshake, then check the server settings for client authentication.

Client Authentication is the ability of a webserver to verify the client, whether it be a browser or other application.

Setting client authentication does reduce the level of security enabled, so this decision should be made based on your needs and threat model.

If you do require client authentication, there are two great articles below:

• HOWTO: Creating your own CA with OpenSSL
• Client Authentication with SSL

If you have any JSSE/OpenSSL questions, feel free to comment and I'll try and get back to you.