In case you can't access the document, here's the short version.
Within the \RUN directory where you've installed Service Manager (for example ..\Service Manager 9.30\Server\RUN) and run a command like the following:
sm -httpPort:13077 -httpsPort:13078 -debugnode:1 -RTM:3 -debugdbquery:999 -log:..\logs\RADtrace.log -debughttp:1 -soap12binding:0
That will start up a debug node and traffic will not automatically be routed to that port from the load balancer, and the log will go into a file called RADtrace.log within the logs directory, and an httplog file within that directory as well.
To access that servlet via the web, you need to make sure that you've modified the web.xml file honorUrlHost and honorUrlPort parameters have been set to true. If not, then you _can't_ access the servlet from the web.
But, if that is set, then you can access that specific servlet by appending &serverHost=HOSTNAME&serverPort=13077 to the end of your URL.