Conflict between UDP multicast and TCP server

[vtomix]

I have a FreeRTOS task for the ipv4 udp multicast rx and an other realize a simple tcp server (both based on the examples). If both task are run the TCP task cant accept connections: Unable to accept connection: errno 113. If only the tcp server is running, it works perfect.
Could be any conflict theoretically between TCP accept() and a configured UDP multicast task? If yes, what could cause this?

[vtomix]

I found the problem. My UDP task uses select(). If I eliminate select() the tcp server accept() works. So the select() is not a thread safe function?

[ESP_Sprite]

Interesting; given that your code is correct, that shouldn't happen. Do you have a sample project that does this so we can take a look at it?