The default network port used by OPC UA (OPC Unified Architecture) for TCP communication is port 4840. This is the standard and IANA-registered TCP port for OPC UA servers. It is possible to configure a different TCP port within the range of 1024 to 49151 if needed, but clients must use the selected port to connect to the OPC UA server. For UDP communication in OPC UA Pub/Sub scenarios, the recommended and default port is also 4840. In summary:

• Default TCP port for OPC UA: 4840
• TCP port can be changed to any port between 1024 and 49151
• Default UDP port for OPC UA Pub/Sub: 4840

This port is used by OPC UA servers to listen for client connections and for network communication using the OPC UA protocol.