The protocol is sent over a UNIX domain stream socket, where the endpoint usually is named wayland-0
(although it can be changed via WAYLAND_DISPLAY in the environment). The protocol is message-based. A message sent by a client to the server is called request. A message from the server to a client is called event. Every message is structured as 32-bit words, values are represented in the host's byte-order.
The message header has 2 words in it:
The first word is the sender's object ID (32-bit).
The second has 2 parts of 16-bit. The upper 16-bits are the message size in bytes, starting at the header (i.e. it has a minimum value of 8).The lower is the request/event opcode.
The payload describes the request/event arguments. Every argument is always aligned to 32-bits. Where padding is required, the value of padding bytes is undefined. There is no prefix that describes the type, but it is inferred implicitly from the xml specification.