Introduction

These are draft notes on OpenSimulator's implementation of the LLUDP ClientStack, a chunk of code which is used to send and receive packets from viewers (clients) implementing the Linden Labs virtual environment protocol.

As such, this stack handles

• Initial setup of an instance of the stack for a viewer.
• Handling of inbound UDP messages from a connected viewer.
• Sending of outbound UDP messages to a connected viewer.
• Throttling of outbound messages.
• Sending and receive of ack messages, both inline within other messages and as standalone messages.
• Resending of messages that are marked as reliable but for which receipt has not been acknowledged by the viewer.
• Throttling of outgoing UDP messages.
• Pooling of clientstack structures (e.g. classes representing messages) in order to improve efficiency and reduce memory usage.

Other references

• Sim Throttles contains very old information on the implementation of throttles. This has likely changed considerably but could still be useful.