4. [Taming blocking functions](./THREADING.md#4-taming-blocking-functions) Enabling uasyncio to handle blocking code.

5. [Sharing a stream device](./THREADING.md#4-sharing-a-stream-device)

6. [Glossary](./THREADING.md#5-glossary) Terminology of realtime coding.

Typical stream devices are a UART or a socket. These are typically employed to

exchange multi-byte messages between applications running on different systems.

When sharing a stream device between concurrent functions, similar issues arise

whether the functions are `uasyncio` tasks or code with hard concurrency. In

the case of transmission of multi-character messages a lock must be used to

ensure that transmitted characters cannot become interleaved.

In theory a lock can also be used for reception, but in practice it is rarely

feasible. Synchronising multiple receiving tasks is hard. This is because the

receiving processes seldom have precise control over the timing of the

(remote) transmitting device. It is therefore hard to determine when to

initiate each receiving process. If there is a requirement to handle

communication errors, the difficulties multiply.

The usual approach is to design the message format to enable the intended

receiving process to be determined from the message contents. The application

has a single receiving task. This parses incoming messages and routes them to

the appropriate destination. Routing may be done by the data sharing mechanisms

discussed above. Error handling may be done by the receiving process or passed

on to the message destination.