When you use a global transaction, you use the communication port for the transaction recovery processing. When you embed a firewall in the system, you must permit communication from this port depending on the firewall configuration. By default, 20302 is used as the port number, but you can change this number.
You specify the settings of the communication port for transaction recovery by customizing the J2EE server properties. For details on customizing the settings for the J2EE server operations, see 3.19.3 Settings for operations in the firewall environment.