PubSub: UDP protocol: sockets should be non blocking when using Pub/Sub schedulers
Description
The UDP sockets are blocking by default but should be used as non-blocking in the Pub/Sub scheduler.
In Pub scheduler: when sending data it is not expected to wait to send on publishing expiration time, therefore we should try again on next publishing interval if it is not possible.
In Sub scheduler: use of WaitSocketEvents / select should guarantee some data is available for read operation on socket but we should also guarantee not to block on read using non-blocking socket.
Edited by Vincent Monfort