While the String RX Port defaults to port 0 in the Eos family software, you should change the port to a different number to ensure good communication. Ports 0 - 1023 are reserved per the IANA: https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt
ETC recommends setting a port in the range 4703 - 4727. The GUI allows port#'s up to 65,535 per the standard.
When you adjust the Port#, make sure to adjust the transmitting software's TX port to the same port number.