Feature request: runtime switching of transport channel

[shvass]

Support for runtime switching of transport (UDP / custom, etc )

Current implementation requires compile time definition for transport type. Adding support for runtime
switching will open possibility of applications to setup backup channel in case main channel fails or create more dynamic applications.

possible implementation

• add a another transport "multimode" apart from UDP, custom, etc which defines multimode implementation. Thus only users with "multimode" bear the overhead of binary size and execution.

multimode

• rmw_uxrce_transport_params_t contains parameters for all possible types. Nothing excluded by macros.

• Add a static global variable "RMW_UXRCE_ACTIVE_TRANSPORT" to determine currently active transport and make transport call as per currently active transport.

• many more

Does this sound like a good idea ?

[pablogs9]

You always can use RMW_UXRCE_TRANSPORT_CUSTOM and use the API to change transports:

https://github.com/micro-ROS/rmw_microxrcedds/blob/jazzy/rmw_microxrcedds_c/include/rmw_microros/custom_transport.h#L54

I've never done that and there might be some implication with regards to RMW initialization or deinitialization.
But at least in theory, micro-ROS RMW custom transport are run-time configured.

[shvass]

I'll definitely try out the "custom transport." But I believed WIFI discovery and other API calls are excluded from compilation when using custom transport. We'll require external implementation for the same.

• Wouldn't it be great if multimode were a core feature of micro-ROS? What are your thoughts on this?
• Would a PR for multimode be considered?