SAP WTS Client connection refused accessing ASE DB in SAP Cloud
Recently I have contributed in the diagnosis of the above connectivity issue in a SAP Data Services over ASE DB project. I am sharing my account of the investigation and the root-cause, which seems to be some confusion over the followings:-
- ASE server configuration affecting the server’s listener(s)
- IP Address resolution of the VM host names referenced in:-
- the ASE server’s interfaces file
- the WTS client’s interfaces file
In essence, the WTS Client’s interfaces file’s target ASE DB query entry refers to a host name and the port number, 4901. The host name is resolved via the hosts file to an IP address, which corresponds to the primary Ethernet NIC (eth0) IP address in the target VM host.
Despite the ASE server starting its listener based on the master entry in the ASE server’s interfaces file and this entry referring to the same pair of VM host name and port number, 4901 as in the WTS Client’s interfaces file, the resolution of VM host name via the hosts file points to another Ethernet NIC (eth2) IP address in the target VM host. As a result, the ASE listener is assigned on the same port number but on a totally different IP address to what the WTS Client is attempting to connect (the network trace on the WTS side confirms TCP SYN request getting a TCP RST, SYN response – the TCP reset gets reported as “Connection refused” as there is no listener on the specified target IP address + port number).
Please refer to the following diagram for the above discussion.
I have created a PPS & PDF files with the full details of the diagnosis and resolutions but these attachment content type is not allowed – please drop me an email if you wish to see the files.