This library is a networking abstraction layer for RollPlayGE, though in principal it's general enough to serve other game engines just as well. It follows a client-server model and uses both TCP (reliable) servicer threads and UDP (low-latency) servicer threads to fulfill separate quality-of-service contracts for different kinds of data.
The server has a single UDP servicer and N TCP servicers, while each of N clients have one UDP and one TCP servicer. Each servicer thread communicates bi-directionally via in-process queues with the main thread.
+---------------------------------------+ +--------------------------------------+
| | | |
| server::* | | client::* |
| | | |
| +--------+ +-----------------------+ +-----------------------+ +--------+ |
| | <---> low_latency::Servicer <----+--> low_latency::Servicer <---> | |
| | Server | +-----------------------+ | +-----------------------+ | Client | |
| | Thread | +-----------------------+ | +-----------------------+ | Thread | |
| | <---> reliable::Servicer <-------> reliable::Servicer <---> | |
| | | +-----------------------+ | +-----------------------+ +--------+ |
| | | . | | | |
| | | . | | +--------------------------------------+
| | | . | | .
| | | +-----------------------+ | .
| | <---> reliable::Servicer <--+ | .
| +--------+ +-----------------------+ | | +--------------------------------------+
| | | | | |
+---------------------------------------+ | | | client::* |
| | | |
| | +-----------------------+ +--------+ |
| +--+ low_latency::Servicer <---> | |
| +-----------------------+ | Client | |
| +-----------------------+ | Thread | |
+----+ reliable::Servicer <---> | |
+-----------------------+ +--------+ |
| |
+--------------------------------------+