The Working of Port Binding is extremely simple.Suppose your phone no. is 01883283840 and the username assigned to you is . When the Bsnl guys a created a username its is not bound with the phone number. the first time you will use your username passowrd . the username is registered in a server in the Local Exchange prefixed by your phone no. and the username become 1883283840bsnl_port. 🙂ashamed: I am not exactly sure if the post fix or prefix the phoneno. :ashamed🙂 either way the phone no is always added to your username . and that become the new username the process is entirely hidden.Suppose somebody else having phone no, 01883265432 has the username password . then when he tries to connect the username become 1883265432bsnl_port and the server refuses the connection because this username doesnot exists. when i got my broadband connection i installed the modem and my bad luck the phone line is down. I was little curious and i had tested the username password on my friend PC it worked. And when next day my phone is working then i got a error the username is not correct. Luckily the JTO dealing in the exchange was an old friend, then he vanishes the old username and gave me the newone , and also explained me how this whole port binding thing worked.😱 Regardless of which IP address you are using your are always port binded 😱