Flash Player uses the Real-Time Messaging Protocol (RTMP) for client-server communication. This is a TCP/IP protocol designed for high-performance transmission of audio, video, and data messages. RTMP sends unencrypted data, including authentication information (such as a name and a password).

Although RTMP in and of itself does not offer security features, Flash communications applications can perform secure transactions and secure authentication through an SSL-enabled web server.

Flash Player also provides support for versions of RTMP that are tunneled through HTTP and HTTPS. RTMP refers to RTMP transmitted within an HTTP wrapper, and RTMPS is RTMP transmitted within an HTTPS wrapper.