Virtual Local IP

Version 1.0

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What is VLIP?

VLIP is a win32 based software that is able to virtually change local IP address for a specified program. This software is able to simulate a public IP address to a workstation in a LAN. Your PC seems to directly connect to Internet, without any limitation of LAN.

Loading a application

Local IP address virtually changed to a public address

But actually this PC only has a private address

Why we need virtual local IP address?

Sharing broadband connection via a router or proxy server is a good idea to reduce expense. But some applications can not properly work within LAN (Local Area Network), even using "forwarding" or DMZ functions. The reason is the Internet application tells other computers its local private address rather than a public address, although the NAT/proxy already forwarded all connections to it.

For example, FTP client must work with passive mode on a LAN workstation. On active mode, FTP client must give FTP server its local address but FTP client only knows its private IP, which is a invalid address in Internet.

In contrast, if a FTP server is in LAN, workstations on Internet may access it via "port forwarding" or "DMZ hosting", which is able to redirect incoming connections to a private address. However, FTP clients can't use passive mode this time.

Therefore we know, if both FTP server and clients are in different LANs, it is almost impossible to build FTP data transfer channel. That is why some personal FTP server could be connected but could not transfer any data.

VLIP is able to solve many problems of Internet applications working within a LAN:

Build a FTP Server within LAN - can't use passive mode
Using a FTP Client within LAN - can't use active mode
Using Chat software with full features (file transfer, video chat etc) in LAN
Overcome some spam-checker for Email Client in LAN
Increasing speed of Peer to Peer downloading software in LAN

Features:

Load a win32 based program and change result of WIN32 API function bind, gethostbyname and gethostname.
Change both host name and IP address of local machine for loaded program.
Change local IP address to specified value for all sub processes/inherited processes of target program. For example, if VLIP loaded program A, program A loaded program B, then VLIP also affects program B.
Automatically get IP address of NAT (Router/Proxy server) by programmable VB script.
Save settings of specified program to a shortcut.
VLIP is developed with win32sdk so it is tiny and fast.

You still need:

A router that supports forwarding/virtual server/DMZ function;

A proxy server that supports forwarding/virtual server/DMZ function.

If your proxy server does not support them, you can try a port forwarding software such as Bounce.

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