Wire format

The protocol is sent over a UNIX domain stream socket. Currently, the endpoint is named \0wayland, but it is subject to change. 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. There is no prefix that describes the type, but it is inferred implicitly from the xml specification.

The representation of argument types are as follows:

• "int" or "uint": The value is the 32-bit value of the signed/unsigned int.
• "string": Starts with an unsigned 32-bit length, followed by the string contents, including terminating NUL byte, then padding to a 32-bit boundary.
• "object": A 32-bit object ID.
• "new_id": the 32-bit object ID. On requests, the client decides the ID. The only events with "new_id" are advertisements of globals, and the server will use IDs below 0x10000.
• "array": Starts with 32-bit array size in bytes, followed by the array contents verbatim, and finally padding to a 32-bit boundary.
• "fd": the file descriptor is not stored in the message buffer, but in the ancillary data of the UNIX domain socket message (msg_control).