The server assigns ihab's and hwnd's - threads' and windows' indexes.
Windows get messages.
Messages are got from either queues, assigned to ihab's, or directly,
if they were sent from the same thread, or indirectly, but without placing into a queue,
if they were sent from another thread of a process. Indirectly - that means it calls a window proc from inside WinGetMsg.
If a message is sent to another process, it is sent via server.
If message is “Sent” - then it's waiting, if it is “Post'ed”, then it put into the process message queue, also inside WinGetMsg
A server by F_CMD_GET_IHAB client's request issues a free ihab, and clientId