@MarceloMarques Thanks I have used Wireshark to do the same and I couldn't find any ip apart from sevice.esri.com(198.102.61.207) relevant to this. As @ChrisUnderwood suggested I went for the same offline method with a small change to avoid email goint out:
1. Generated the "authorize.txt" file
2. Logged in to the myesri.com with any organization account
3. Opened the "https://my.esri.com/#/licensing/activations/secure-site" web page
4. uploaded the authorize.txt file
5. Generated the "authorization.ecp" file
6. Copied to the Server and opened it using "Sofware Authorization Wizard"
7. Click OK
The above method helped me.
Thanks a lot.