PeopleSoft Community Network
When an inbound integration does not specify an NODE then the message is processed by the Default Application Server. This is an optional default found on the Gateway > Gateway Setup Properties.
I've noticed that some delivered Oracle images don't have the correct configuration for the default.
The Tools Release field must include the patch release number.
If this is not present or is incorrect then you'll get a null response when you invoke a service and an error is logged in PSIGW/errorLog.html (note: this is case sensitive).