The story of messaging service port

I want to make a deep research on the two msg srv port parameters rdisp/msserv and rdisp/msserv_internal this weekend. After

[Updated @ 10.20.08]

In SAP's NetWeaver Platform architecture, one Instance is also called an application server. For each instance, as a server, has its instance number and system ID for being identified. Accordingly, a SAP system must be an AS ABAP, AS Java or AS ABAP & Java system.

For ABAP system or ABAP+Java System, we always need a central instance for controlling, dispatching, etc. And the Message Server is one kind of service provided by the SAP System for internal and external communication, therefore the message server is 'located' in the central instance of an ABAP system or an ABAP&Java system.

Each instance also has its own profile, which located under the '<sapmnt>/usr/sap/<sid>/SYS/profile', to configure some parameters of the instance. 'rdisp/msserv' and 'rdisp/msserv_internal' are two common parameters in the profile.

Now let's have a look at the document about these two parameters.

For rdisp/msserv:

For rdisp/msserv_internal:

Obviously, rdisp/msserv is used for external communication and rdisp/msserv_internal is used for internal communication between Dialog Instances and the Central Instance.

As the description says, the rdisp/msserv is and only is defined in the Default.PFL file and the rdisp/msserv_internal should be defined as a free port number in the default profile.

But in the central instance's and the central service instance's instance file. Respectively, we should also deactive the external msg port via setting it 0 and activate the internal msg port by assigning another port number to it. Actually, in an ABAP+Java system, we should set the value of the rdisp/msserv_internal equal to the value of 'j2ee/ms/port' because the central service instance should communicate with the j2ee related stuff thru this port, and the central instance should communicate with the central service instance by the same port.