Technical RFC Integration On-Premise-EWM 9.5 to Cloud Public 25/02

[ThArndt]

Background / Sceanrio:

• We are setting up an integration between our On-Premise SAP EWM 9.5 and our Cloud Public  S/4 HANA 25/02.
• In this scenario the Cloud Public is the “ERP” System and integrates to the “External” EWM 9.5 which is hosted within our company network.
• The communication between the two systems is based on RFC - Remote Function Calls (Communication Scenario 0247).
• We managed to establish the RFC communication FROM the Cloud Public TO the On-Premise EWM 9.5. This means, Master Data can already be replicated FROM Cloud Public TO the EWM via CIF (using RFC calls) and we can transfer Orders (e. g. Inbound) FROM Cloud Public TO the EWM 9.5
• To have a full function integration via RFC Calls between the two systems it must also be possible to make RFC Calls FROM the On-Premise EWM 9.5 TO the Cloud Public (e. g. to send the Outbound Delivery order after Goods Issue posting).
• We tried to setup this direction as described e. g. in documentation 2VJ_Set-Up_EN_XX.pdf (Setting Up SAP EWM Integration - Inbound Processing from Supplier (2VJ)).

Now the problem we are facing:
One of the first steps in the Integration guidelines is to setup the RFC connection in the On-Premise system to reach out TO the Cloud Public System. In other words a communication from our company internal network towards the Cloud Public is to be established.

Whatever we tried to setup in the On-Premise EWM 9.5 and/or our Cloud Connector fails as we can not "reach" the Cloud Public system

Our Question

1. Is it a MUST, to open the firewall / Internet security settings to allow network traffic from the On-Premise network to The SAP Cloud Public system?
   OR
2. Do we have to establish the connection from On-Premise towards Cloud Public using special setup on the Cloud Connector / Within the BTP or something like a "Public Cloud Proxy server", etc. (if yes, can SAP provide a documentation on how to do so)?

[simon_luser · Accepted solution]

I'm not familiar with Communication Scenario 0247, but generally you have two options:

1. Using WebSocket RFC from OnPrem to Cloud - you need to expose the cloud endpoints and they must be reachable from your OnPrem network.
2. Using classic RFC with Cloud Connector via a Service Channel. 

Are you currently using WebSocket RFC for the other direction (Cloud to OnPrem) or do you use Cloud Connector?

[ThArndt · Accepted solution]

Hi Simon, thanks for your input. To pick up your points.

[ThArndt · Accepted solution]

Point 1) The general guideline for the Integration part on the -Premise system points out to use RFC Connection Type 3 (Connection to ABAP system) - How would I setup the WebSocket RFC within the EWM 9.5 On Premise. What setting is required then on the Public Cloud system to be able to consume the RFC calls?,

[simon_luser · Accepted solution]

If connection type 3 should be used, then you need to use option 2).

I don't know which ABAP version EWM 9.5 is based on, and if WebSocket RFC is also available for your specific integration scenario.

[ThArndt · Accepted solution]

Point 2) We tried this variant via our cloud connector, but testing the service channel fails with error message "Service Channel could not be opened"

[simon_luser · Accepted solution]

Please open a support incident for that then.

[Ulrich_Schmidt · Accepted solution]

To add a few points: for communication across the internet, WebSocket-RFC is much better suited than the classic CPIC-based RFC. Therefore I would strongly recommend option 1 in Simon's answer. For this there are two possibilities:

1. The SAP_BASIS release of your EWM 9.5 system is "new enough" (release 19/09 or newer).
   Then you can simply create a destination of type "W" in SM59, which points to your Cloud system.
   To answer your question about firewall: you don't need to open your firewall for this, but you need to have an HTTP Proxy that allows outbound HTTPS traffic (at least to the IP addresses of your Cloud account). In the type "W" destination, you can then specify this HTTP Proxy, which will then be used for the WebSocket connection to the Cloud system. The technical connection then looks like this:
   EWM  ---WebSocket-RFC---> HTTP Proxy ---> Cloud system
   
   
2. The EWM 9.5 system is "too old" (older than 19/09).
   Here it is still possible to use WebSocket-RFC by adding an extra step in form of a SAP Business Connector, which can convert classic RFC protocol to WebSocket-RFC protocol:
   EWM ---CPIC-RFC--->  SAP Business Connector ---WebSocket-RFC---> HTTP Proxy ---> Cloud system
   
   This setup is described here: WebSocket RFC to Cloud Using SAP Business Connector | SAP Tutorials (short tutorial)
   and here: WebSocket RFC to Cloud Using SAP Business Connecto... - SAP Community (detailed description including extra security settings, necessary steps in all three components and some technical background)

[ThArndt · Accepted solution]

Hi Ulrich, thanks for the information. That's exactly what I have been looking for. Bad enough we have to go the "full" way, as the EWM 9.5 is to old to offer the "W" type for the RFC connection. Let's, if we can get the setup done now.