rfc6455-websocket

After a successful handshake, clients and servers transfer data back
and forth in conceptual units referred to in this specification as
"messages". On the wire, a message is composed of one or more frames. The WebSocket message does not necessarily correspond to a
particular network layer framing, as a fragmented message may be
coalesced or split by an intermediary.
A frame has an associated type. Each frame belonging to the same
message contains the same type of data. Broadly speaking, there are
types for textual data (which is interpreted as UTF-8 [RFC3629]
text), binary data (whose interpretation is left up to the
application), and control frames (which are not intended to carry
data for the application but instead for protocol-level signaling,
such as to signal that the connection should be closed). This
version of the protocol defines six frame types and leaves ten
reserved for future use