2947990 - Error when opening an RFC connection (CM_PRODUCT_SPECIFIC_ERROR or CM_RESOURCE_FAILURE_RETRY)

The RFC call in SM59 (ABAP connections, type: 3) was not successful because of the following communication failure:

Error when opening an RFC connection (CPIC-CALL: 'ThSAPOCMINIT', communication rc: CM_PRODUCT_SPECIFIC_ERROR (cmRc=20)

or

Error when opening an RFC connection (CPIC-CALL: 'ThSAPOCMINIT', communication rc: CM_RESOURCE_FAILURE_RETRY (cmRc=27)

Connection test results:

Logon Connection Error
Error Details Error when opening an RFC connection (CPIC-CALL: 'ThSAPOCMINIT', communication rc: CM_PRODUCT_SPECIFIC_ERROR (cmRc=20).
Error Details ERROR: partner 'target hostname:sapgwXX' not reached
Error Details LOCATION: SAP-Gateway on host "local hostname" / sapgwXX
Error Details DETAIL: NiPConnect2: XX.XX.XX.XX:33XX
Error Details CALL: connect
Error Details COMPONENT: NI (network interface)
Error Details COUNTER: 7945
Error Details ERROR NUMBER: 111
Error Details ERROR TEXT: Connection refused
Error Details MODULE: /bas/7XX_REL/src/base/ni/nixxi.cpp
Error Details LINE: XXXX
Error Details RETURN CODE: -10
Error Details SUBRC: 0
Error Details RELEASE: 7XX
Error Details TIME: Thu Jan XX XX:XX:XX 2024
Error Details VERSION: 40

• Operating System independent
• Database independent
• SAP NetWeaver
• SAP Web Application Server for SAP S/4HANA
• ABAP Platform 

RFC call;  Error when opening an RFC connection (CPIC-CALL: 'ThSAPOCMINIT', communication rc: CM_PRODUCT_SPECIFIC_ERROR (cmRc=20); SM58; Connection Test; niping -v -H; Lookup of IP-Addr; NiAddrToHost; /etc/hosts; CALL_FUNCTION_SEND_ERROR; Finished status; asynchronous; CALL FUNCTION STARTING NEW TASK; cm_product_specific_error/ni_read_failed , KBA , BC-CST-GW , Gateway/CPIC , BC-MID-RFC , RFC , Problem