Hi,
We used LwIP in similar scenario, but with one task responsible for this socket/netconn.
Using internal RTOS queues to pass data to this single task was relatively simple, and all multitasking problems were avoided.
Are there any reasons you cannot use this socket in single thread with external mechanism for aggregating data from multiple senders?
Fabian, I guess this can be implemented in LwIP in a way to allow such use scenario, but wouldn't it be extra code to test/maintain for current maintainers?