Editing SimTX API v24 (section)

== Design notes ==
A few properties of the protocol are worth knowing before writing any code, because they explain most of its sharp edges:

* '''No length prefixes.''' Packets are an ID byte followed by a body whose layout the reader must already know. Reading one field too few or too many silently misaligns everything after it. Write the decoder carefully, and test it against a real server early.
* '''Silence is an answer.''' Several kinds of failure, especially invalid receiver requests and limit rejections, are reported by closing the connection without a message. When the socket closes right after a request, the request was probably invalid or over a limit. [[SimTX API v24/Limits and errors]] lists the cases.
* '''Exact version match.''' Server and client must both speak version 24. There is no negotiation and no backwards compatibility. A server that moves to a new version rejects old clients with a clear [[SimTX API v24/Packets/HandshakeResult|HandshakeResult]] rather than misbehaving.
* '''Real time.''' Receivers get samples at the rate of the simulation, and transmitters must send samples at the rate they declared. Neither side waits for the other. A client that falls behind loses data.
* '''Physics, not a jukebox.''' The IQ a receiver gets is what an antenna at that location would deliver: propagation, fading, noise and interference included. A station that cannot be heard is often simply out of range, or on the wrong side of the day–night terminator. See [[Propagation Basics]].