WebSocket RFC to Cloud Using SAP Business Connector

The following tutorial describes how to establish a connection between an on-premise ABAP system and a cloud-based ABAP system.

Technically, the connection works as follows:

1. The on-premise ABAP system makes an RFC request for an RFC destination of type T.
2. At this RFC destination, an SAP Business Connector (SAP BC) is registered. It receives the request, transforms it into a WebSocket/HTTPS-based request and forwards it to the cloud-based ABAP system.
3. The cloud-based ABAP system processes the request and returns the response back to the SAP BC.
4. The SAP BC transforms the response back to classic RFC protocol and returns it to the originating on-premise system.

SAP BC acts as a middleware between the classic CPIC-based RFC protocol and the WebSocket-based RFC protocol that can be tunneled through firewalls into the cloud without problems.

If the on-premise ABAP System is an S/4HANA version 1909 or newer, the underlying ABAP platform can perform WebSocket RFC calls without any additional component. The business connector is not required in this case.

In the source system, you need to setup an RFC destination of type T and allow SAP BC to register at this destination. The source system will later send all RFC calls, which are intended for the cloud system, to this RFC destination.

In the source system (the on-premise system), set up an RFC destination of type T.

1. Run transaction SM59.
2. Choose create.
   • Destination: MYDESTINATION_XXX
   • Connection Type: T RFC connection to external program using TCP/IP
3. (Optional): Enter a meaningful description.
4. On tab Technical Settings, make the following settings:
   • Activation Type: Registered server program
   • Program ID: CLOUD_SYSTEM_VIA_BC
   • Gateway Host: Hostname of one of the application servers of the on-premise system, which still has some free capacity.
   • Gateway Service: sapgwXX, where XX is the instance number of the on-premise system.
5. Go to tab Unicode.
   • Make sure that here Unicode is selected.
6. Save the destination.

If there is already a line like P TP=* HOST=*, you can skip this step.

1. Run transaction SMGW.
2. Choose Goto > Expert Functions > External Security > Maintain ACL Files.
3. Go to tab Reginfo File.
4. Choose Insert Line > Standard.
   • P/D (*): P
   • TP (*): CLOUD_SYSTEM_VIA_BC
   • Host: Host/IP where SAP BC will run, e.g. 10.87.64.3

   You can find out the IP in the command line. On Windows, enter ipconfig. On Mac or Linux, enter ifconfig. Copy the IPv4 Address.

   • Access: internal
   • Cancel: local
   • No: Leave this field unspecified.
   • Choose Save.
   • Save your settings globally.
   • Choose Goto > Reread (global)

In releases older than 7.40 SP11, you have to change the Reginfo file manually. See SAP Note 1989587 for more information.

To provide a service in the cloud system, you must create the following entities:

• Communication user
• Communication system
• Communication arrangement

This procedure is the same as for other connection types. See Overview of Communication Management for more information. In this tutorial, you don’t need to create a communication scenario as we use the SAP-delivered scenario SAP_COM_0636. This scenario provides access to the following function modules:

• RFC_METADATA_GET
• RFC_FUNCTION_SEARCH
• RFC_GET_FUNCTION_INTERFACE
• DDIF_FIELDINFO_GET

However, you can also use your remote-enabled function module with a custom communication scenario. See Develop a Remote-Enabled Function Module (RFM) and Communication Scenario for more information.

1. Login to Fiori Launchpad in the target cloud system.
2. Choose Communication Management > Maintain Communication Users.
3. Choose New.
4. User Name: BC_USERXXX
5. Description: User for SAP BC
6. Password: PasswordForBC_USERXXX
7. Choose Create.

1. In Fiori Launchpad, choose Communication Management > Communication Systems.
2. Choose New.
   • System ID: MY_SYSTEMXXX
   • System Name: MY_SYSTEMXXX
3. Activate Inbound Only.
4. Under Users for Inbound Communication, choose Add.
   • Choose user BC_USERXXX.
   • Choose OK.
5. Save the communication system.

1. In Fiori Launchpad, choose Communication Management > Communication Arrangements.
2. Choose New.
3. Search for communication scenario SAP_COM_0636.
4. Arrangement Name: MY_ARRANGEMENTXXX
5. Choose Create.
   • Communication System: MY_SYSTEMXXX
   • Copy the API-URL.
6. Save the communication arrangement.

1. Start SAP BC.
2. Go to Adapters > SAP.
3. Choose Add SAP Server.
   • Name: Connection_to_Cloud
   • Connection Type: WebSocket Connection
   • Logon Type: User/Password
   • User: BC_USERXXX
   • Activate Alias User.
   • Password: PasswordForBC_USERXXX
   • Client: Client of the target cloud system (optional)
   • WebSocket Host: API-URL of the communication arrangement without the https:// prefix

   Including the https:// prefix leads to an error when you test the connection.

   • WebSocket Port: 443
   • Network: WAN
   • Choose Save.
   

4. Download the certificate of the target cloud system. We recommend using the browser’s “show certificate” functionality. Most browsers provide information on the security status of the SSL/TLS connection, usually displayed as a small lock icon. Select this icon and save the CA root certificate to file. We recommend to use Chrome browser for this.

   

5. Add the cloud system’s certificate to the trusted list in SAP BC.

   • Copy the certificate to the CA certificate directory of SAP BC. In this tutorial, the directory is in C:\sapbc481\Server\config\trust
   • Go to Security > Certificates and choose Trusted Certificates > Reload CA List.
   If your corporate firewall requires an HTTP proxy for outbound connections, you need to make this proxy known to the SAP BC. For this, go to Settings > Proxy Servers > Secure Proxy (HTTPS) and enter the host, port, and, if necessary, user information of your proxy server. Here, only basic proxy authentication can be configured.

6. Test the connection. Select the newly configured SAP server form the server list and choose Test Connection.

1. In SAP BC, choose Adapters > SAP.
2. Choose Add SAP Server.
   • Name: Connection_to_OP
   • Connection Type: CPIC Connection
   • Application Server: Hostname of your application server (= gateway host defined in your destination in step 2)
   • System Number: The instance number you used in step 2
   
   • Choose Save.
3. Go back to the SAP Servers list and choose 0 in the Listeners column of Connection_to_OP and choose Add Listener. This will create a so-called RFC Listener, which will connect to the RFC destination that we created in the on-premise system via transaction SM59.
   • Connection Type: TCP/IP
   • Program ID: CLOUD_SYSTEM_VIA_BC
   • Number of Threads: 5
   • Gateway Host: Hostname of your application server (= gateway host defined in your destination in step 2). This field is filled automatically.
   • Gateway Service: The gateway service you used in step 2
   • Repository Server: Connection_to_Cloud

   Using the target cloud system as repository server has two advantages:

   • A function module must exist in the system, where it is to be executed. However, the same does not apply to the source system. Therefore, by letting SAP BC make the DDIC lookup in the cloud system, the on-premise system can call function modules of the cloud system, that do not exist in the on-premise system.

   • By using the cloud system for the DDIC lookups, the SAP BC does not need user credentials for the on-premise system.

   
   • Choose Save.
   • Start the listener. Choose the red button in column Started?.

Define what SAP BC shall do with the incoming RFC requests. In our case, we simply instruct SAP BC to send everything that it receives from the on-premise system to the target cloud system.

1. In SAP BC, choose Adapters > Routing > Routing Rules.
2. Under Add Routing Rule, enter the following:
   • Sender: Enter your the system ID of the on-premise system with the current client, for example YI3000.
   • Receiver: MYDESTINATION_XXX
   • Message Type: *

3. Choose Add.

   • Transport: RFC
   • Destination: Connection_to_Cloud
   • Choose Save.
   • Activate the rule by choosing No in column Enabled?.
   

1. Run transaction SM59.
2. Choose your destination MYDESTINATION_XXX.
3. Choose Connection Test.