1. DCS230 Centralized or Decentralized Data Transfer Prof. Nalini Venkatasubramanian -Myung Guk Lee -YunHo Huh -Abhinav

2. Purpose Share data and files in mobility storages Communicate between smart-phones and Computers through 3G network and Wi-Fi.

3. Challenge How to connect with other devices? How to implement an Data sharing application for smart-phones. 3G Wired Network 3G WiFi App ? ?

4. Technical Reports (3G) Constraints  Service providers’ NAT Impossible to make a direct connection Dynamically given IP address  Protocol?  Service providers users use

5. Technical Reports (3G) Internet client server Service providers’ NAT accept Internal IP A No given Internal IP External IP A No given external IP

6. Technical Reports (3G) Solutions  Service providers’ NAT We created our own proxy server Server (Active mode FTP with our own protocol) Client (Passive mode FTP)  Protocol Modified FTP protocol to adapt our model

7. Technical Reports (3G) Solutions  Handle incoming clients Set up another command line  No matter which service providers Even if two users are using same service providers, there is a possibility each device is under different NAT.

8. Technical Reports (3G) Proxy client server Service providers’ NAT Internal IP AInternal IP B External IP A External IP B accept

9. Proxy(like) Server Features Proxy server – 2 Modules 1) Client side Module 2) Server side Module Client side Passive FTP Server side Modified Active FTP

10. Proxy Server set up PROXY SERVER ANDROID FTP CLIENT ANDROID FTP SERVER DATA CONTROL PROXY COMMAND

11. THANK YOU