In the transaction code SMT1 (Trusted-Trusting Connections) status check, you found below error message under the description,
Error when opening an RFC connection
(LB: Hostname or service of the message server)
You can capture more error in details from the transaction code SM59. Locate the trusted / trusting connection and perform the connection test. Similar error as below,
Logon Connection Error
Error Details Error when opening an RFC connection (LB: Hostname or service of the message ser
Error Details ERROR: service 'sapmsSID' unknown
Error Details LOCATION: SAP-Server ITSITI on host DAERA (wp 26)
Error Details DETAIL: NiPGetServByName: 'sapmsSID' not found
Error Details CALL: getaddrinfo
Error Details COMPONENT: NI (network interface)
Error Details COUNTER: 28
Error Details MODULE: ninti.c
Error Details LINE: 933
Error Details RETURN CODE: -3
Error Details SUBRC: 0
Error Details RELEASE: 722
Error Details TIME: Mon May 04 07:40:16 2020
Error Details VERSION: 40
Solution
Login to the operating system level and go to below directory,
C:\Windows\System32\drivers\etc
Add the missing entry into the services file. Example,
sapmsSID 3601/tcp # SAP System Message Server Port
Once done, do the connection test again. It should be working fine now.
