Often, connectivity issues arise when something is hindering access to a specific port or hostname. This obstruction can be due to a firewall blocking the connection or the service-hosting process not listening on the designated port. This could result from the service not running, or it might be listening on an alternative port. Consequently, establishing a connection becomes impossible.
To diagnose the problem, you can try running the netstat -anb command from the command line to check if anything is listening on the intended port. If it returns no results, consider changing the port number. In Windows operating systems, you can use the netstat command via the command line (cmd.exe), while on Linux, you may need to use netstat -anp.
Occasionally, when the target machine 'actively refuses' the connection, it could be because the server's 'backlog' is full. In such cases, you might consider increasing the server's backlog, but it's also essential to implement retry logic in your client code to handle this situation. This is necessary because even with an extended backlog, the server could be handling numerous other requests on the same port at that time.
