How to find out if the client is able to reach the SAP server perfectly?

This can be diagnoised using NIPING.EXE command, which is available in Exe -> Run directory. To test the connectivity between SAP and front end computer, do the following:

First start the NIPING server on computer:

Nipping –s –I 0

Then start the same on the client. Use the following command:

Nipping –c –h