[dist4]message_header  // num_bytes
[u4]1                  // version
[u4]0                  // interface ID
[u4]1                  // name: Method1 does not have a response message.
[u4]2                  // flags: kMessageIsResponse
[u4]0                  // padding
[u8]1                  // request_id
[anchr]message_header