iAnywhere.Data.SQLAnywhere.SAException Connection error: Connection was dropped (may not be a SQL Anywhere server)

While trying to connect to SQLAnywhere (Sybase) database (C# code) from Azure ServiceFabric:

await using var connection = new SAConnection(connectionString);
await connection.OpenAsync();

receive iAnywhere.Data.SQLAnywhere.SAException

Connection error: Connection was dropped (may not be a SQL Anywhere server)

Error code is Error 832. This is generic connection error: An error occurred while attempting to establish a connection with the database server, but before attempting to connect to a database. Failure to initialize a communication link during the connection attempt is an example of this error. Creating a debug log file using the LogFile connection parameter may provide more information.

Locally it works, but does not work from Service Fabric.

Fix ideas tried:

1. Missing driver? Looks like no, Sybase (now SAP) SQLAnywhere requires special driver or client - but locally also works without this driver, just with iAnywhere.Data.SQLAnywhere.NETCore nupackage installed
2. Network connection/ firewall problems? Looks like no, database server can be pinged from Service Fabric node

It was another traffic protection tool. Although it was possible to telnet the port, still traffic from app was blocked by another tool.