Build an SAP RFC Server using the SAP .Net Connector

This blog post describes step-by-step how to use the SAP .Net Connector and Microsoft C# to create an SAP RFC Server. This allows an SAP process to call your custom C# code, which can accept parameters and return values.

The SAP .Net Connector simplifies creating C# programs that can interoperate with an SAP host. The SAP .Net Connector is available from the SAP Service Marketplace. You must have access to the SAP Service Marketplace to be able to download the SAP .Net Connector. The SAP .Net Connector must be installed on your development machine before we begin.

RFC is a Remote Function Call. In this case, the SAP process is a ‘client’ that is making an RFC call to our custom ‘server’ code. Our code uses the SAP .Net Connector to register on an SAP Application Gateway.

The TLA system we have been creating exists solely to demonstrate certain programming techniques involving the SAP .Net Connector and C#.  We will cover three separate parts of the solution: defining the function to SAP, creating a proxy object used to access SAP, and creating our C# code to perform the RFC function.

Defining the Function in SAP

Before we build our RFC server, we will define our RFC function in the SAP system. There are two parts we will need to create:  the Function Signature, and the RFC Destination.

Defining the RFC Function Signature

Open the SAP SE37 Function Builder screen. For the Function Module field, enter Z_RFC_TLA_HELLO_WORLD and click Create. For the Function group, press the browse button to the right of the field, then select an appropriate function Group. Enter a short text description and click Save to save the function signature.


On the Attributes tab, be sure to select the Remote-enabled module radio button.


Now we will be asked to define the parameters that are used. SAP refers to values passed to the RFC call as Import values. Values that are returned from the RFC call are called Export values.

In the Function Builder screen, on the Import tab, define a Parameter named Name. Fill in the appropriate Type and Associated Type values. Be sure to check the Pass Value check box.


On the Export tab, create a Parameter named Hello_World. This will end up storing the result of the RFC call. Define the field in the same way as the Name import field.


Save your RFC Function. Then you need to activate your RFC function. To do that, from the SE37 screen, enter the function module name. then click the Activate button.


Defining the RFC Destination

SAP can direct an RFC call to different destinations. We will create an RFC Destination using SAP function SM59. This RFC Destination is used by the SAP system to route an RFC call to our program, which previously registered itself on the SAP Application Gateway.

In the SM59 screen, click the Create button.  Enter RFC destination of TLARFCSERVER. The Connection type is T for TCP/IP. Enter a description.

On the Technical settings tab, select Activation Type of Registered Server Program.

For the Registered Server Program Program ID, enter TlaRfcSrv. The Program ID we use here must match the Program ID used when our server code connects to the SAP Application Gateway.


If you try the Test connection button, it will fail, since we have not yet registered our program on the Application Gateway. Later, we can come back to SM59 and test this and see that our RFC destination is available.

C# Code

We will create an application that can be called from an SAP host. The SAP host will pass in a name, as a string. Our application will return a hello greeting back to the calling program.

Our solution will consist of two parts.

  1. The first part is the SAP .Net Connector Proxy project, named TlaRfcServerSapProxy. This will produce a Dynamic Link Library that encapsulates what we need to know to interoperate with the SAP host.
  2. The second part is is our custom code project, named TlaRfcServer. This contains the code which will execute when called from the SAP host via RFC. Save the RFC destination.

Creating the SAP Proxy Project

We will use Visual Studio 2003 to create a DLL that manages the interactions with the SAP host. The SAP .Net Connector version 2.0 works with Visual Studio 2003 or 2005. To use the .Net Connector in our preferred environment of Visual Studio 2008, we will create the proxy DLL in 2003 and add that to our 2008 project. The techniques are described in our earlier post, Using the SAP .Net Connector in Visual Studio 2008.

In Visual Studio 2003, start a new Class Library project named TlaRfcServerSapProxy. Delete the default Class1.cs file that is created automatically.


From the Solution Explorer, Right-click on References and choose Add New References. Under the .Net tab, highlight SAP.Connector.dll and SAP.Connector.RFC. Click the Select button, then OK to add the SAP .Net Connector references.


Now add the SAP Connector Proxy to our project. Right click on the project and choose Add / Add New Item. Under the templates, highlight SAP Connector Proxy. In the Name field, give our proxy the name TlaRfcServerSapProxy.sapwsdl. The name we use here will become the object type name for our SAP Server Proxy object we use when we build our RFC server code.


The TlaRfcSerfverSapProxy.sapwsdl file will be displayed in Design mode. Right click on the Design surface and choose properties. This displays properties of our SAP Connector Proxy. Change the Proxy Type to Server.


Now we need to add in a reference to our SAP host so that we can pull in the signature and object model for our RFC function. Open the Server Explorer windows and expand SAP / Application Servers. Right-click on Application Servers and choose add New Server. Enter in the connection information for your SAP host. Click OK.

Expand the newly added SAP Server and right-click on Functions. Choose Add New Function Filter. In the Name Filter field, enter *HELLO* . The * is used as a wild card. Click OK to display our Z_TLA_RFC_HELLO_WORLD function in the Server Explorer.


Highlight the Z_TLA_RFC_HELLO_WORLD function in the Server Explorer, and drag it onto the TlaRfcServerSapProxy.sapwsdl design surface. This will add the necessary function signatures and object type definitions to the project.


Now attempt to build the project. It will fail, as we have not yet created the code to implement our remote function. But, when we ran the build, the SAP Connector generated an implementation stub for our server method. A new class was automatically added to our project, named TlaRfcServerSapProxyImpl.cs.

However, we desire to implement our RFC server using Visual Studio 2008.

So, we will modify this code so it will build, and later we will override the implementation from our Visual Studio 2008 project.

If you double-click on the build error, it will take you to the offending line of code. All we need to do is set the result of Hello_World to some value.  To prevent confusion with our Visual Studio 2008 code, we will just return foo.


Now build the TlaRfcSapServerProxy project and it will create TlaRfcServerSapProxy.dll, which we will use in our Visual Studio 2008 project.

Creating the RFC Server Project

Using Visual Studio 2008, create a C# console project named TlaRfcServer. In the Solution Explorer, right-click on References and choose Add New Reference. Using the Browse tab, select both SAP.Connector.dll and Sap.Connector.Rfc.dll, typically found in C:\Program Files\SAP\SAP .Net Connector 2.0.

Add a reference to the TlaRfcServerSapProxy.dll created earlier, also using the Browse tab. Add a reference to System.Web.Services using the .Net tab.


In our C# code, we need to provide the code to implement our RFC function, which we do by inheriting from TlaRfcServerSapProxyImpl and overriding the Hello World function.


On Line 3, with have our ‘using’ directive to include our custom proxy.

On line 8, we are creating a new class named SAPProxy, which is derived from our TlaRfcServerSapProxyImpl class that was created in our Visual Studio 2003 class.

On line 12 is the override of the Z_Tla_Rfc_Hello_World call. We provide our functionality and place the result in the Hello_World variable.

That concludes our class that will implement the RFC functionality.

Now we will finish off our console program so that we can establish our code on the SAP Application Gateway and execute it.

To do this,we will pass in command line arguments to our Main routine. These arguments are passed to the SAPProxy constructor, which uses them to connect to the correct SAP Application Gateway.

Each of our SAP Proxy objects are hosted by an SAPServerHost object, which is part of the SAP .Net Connector. The SAPServerHost object governs the connection to the SAP host.

Once we create the SAPProxy object and attach it to an SAPServerHost, we can start the host and that will cause our program to register and be available on the SAP Application Gateway.

Our program will continue to be available on the SAP Application Gateway as long as we have it running (until we press the enter key, in our example).


On lines 22-25, we instantiate our proxy and SAP host. Notice how we pass in the command line arguments to the SAPProxy constructor (line 25).

We start the proxy on line 29. After we have done that, we can go back to the SAP SM59 function and test our RFC destination. If things are working, that test will success.

Our code will continue to be available until we press enter at line 37, after which we stop the SAP host.

Command Line Arguments

The command line arguments consist of three parts, and are specified in the Visual Studio environment under the Debug tab of the Project Properties display.

The three parts are

-aProgram ID



The Program ID specified here must match the Program ID we used when creating the SAP RFC Destination. In our case this is specified as –aTlaRfcSrv.

The Port field tells SAP what TCP/IP port to use. This is specified by –XSAPGW00. The SAPGW part specifies port 3300, we add whatever the 00 is to get the actual port number. In our case we are using port number 3300, so we use –XSAPGW00. If we wanted port 3302, we would have used –XSAPGW02.

The Host field is the DNS name or IP address of the SAP server.

So, your parameters will be different but they will look something like –aTlaRfcSrv –XSAPGW00 –Ghostname


Now build and run TlaRfcServer. A console window will appear.

Go back to SAP and bring up the SM59 screen. Expand the TCP/IP connections and find TLARFCSERVER. Double click that to display the definition. When you click the Test Connection button, you should see something like :


which indicates a successful test of the RFC destination.

Now we need to test our actual RFC function. Bring up the SAP SE37 screen. In the Function Module name, enter Z_TLA_RFC_HELLO_WORLD, which matches the name of the function signature we created earlier.

Press the F8 key to test the function. The Test Function Module screen is displayed.

For the RFC Target sys, we use the RFC Function destination we created earlier, TLARFCSERVER.

For the name field, type WORLD. Press F8 to execute the RFC call.


This indicates a good test of our RFC function.


If things don’t work, check the following:

Program ID in RFC Destination matches –a parameter of TlaRfcServer command line.

Port number (SAPGW00) on TlaRfcSever comand line is set to correct port number.

Any firewalls in between the SAP host and the RFC Server program need to allow traffic in both directions over that port.


In this blog posting we have shown how you can call custom C# code from an SAP process.


  1. Hi there,

    I followed each step accoring to the post, but I keep receive error when try to test the TCP/IP connection, the error message says the program is not registered, is there any idea where might cause this problem or did I missed anything?
    Thanks in advance!

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