open port in d-link DSL-2640R
1-enter this adresse in the browser: 192.168.1.1
2-enter username and password: by default the username is admin and the password is admin
3-click Advanced
4-choose Port forwarding
5-click Add button
6-private ip: enter your computer ip in local network
  protocol Type:ALL TCP/UDP
  Public start port: the port you want to open
  Public End port: put the same value u put in public start port or heigher value if u want to open a ports range.
  Connection:PVC0 or PVC1...
7-Apply