Can't receive socket data when renaming socket


I’m working on an URCAP which communicates with 2 different sockets.
When opening the sockets, I added in parameter the socket names that I wanted


After sending some data to the socket, I try to receive a response using

received_data = socket_read_string("socket_ucr",timeout=5)

I don’t get any answer. However, if I change the socket_name by its default value (“socket_0”), it works.
Did I miss anything about the naming rules of sockets?