  In this paper we investigate lossy channel games under incomplete
information, where two players operate on a finite set of unbounded FIFO
channels and one player, representing a system component under consideration
operates under incomplete information, while the other player, representing the
component's environment is allowed to lose messages from the channels. We argue
that these games are a suitable model for synthesis of communication protocols
where processes communicate over unreliable channels. We show that in the case
of finite message alphabets, games with safety and reachability winning
conditions are decidable and finite-state observation-based strategies for the
component can be effectively computed. Undecidability for (weak) parity
objectives follows from the undecidability of (weak) parity perfect information
games where only one player can lose messages.
