Author: Etienne Dechamps (a.k.a e-t172) [email protected]

https://github.com/dechamps/WinIPBroadcast

WinIPBroadcast is a small program that allows Windows applications to send global IP broadcast packets (destination address 255.255.255.255) to all interfaces instead of just the preferred one.

This application is most useful for users of server browsers or other network monitoring software. Specifically, those playing multiplayer games locally on multiple interfaces (for example, a LAN network and a Hamachi VPN) will be able to see games from all networks at once.

WinIPBroadcast is an open source (GPL), extremely small (450 lines, 15KB executable) C program. It works "behind the scenes" as a service without any user interaction. Its memory usage is 1MB. When you're not sending any broadcasts, its CPU usage is strictly zero.

Windows 7 only sends global IP broadcast packets (destination address 255.255.255.255) on the interface which matches the preferred route for 255.255.255.255 in the route table.

More often than not, this isn't what you want: software that makes use of global broadcast packets (e.g. server browsers, games) expect these packets to be sent to all interfaces in order to reach all the local hosts your computer has access to.

For example, consider a computer which is simultaneously on a LAN and on a VPN. The user is a video game player who sometimes use multiplayer on the LAN, sometimes on the VPN with a few friends. Unfortunately, the game uses global broadcast packets to discover open games on the local network. Consequently, the player will only be able to see games on one network: the LAN or the VPN, depending on his routing table (most probably the LAN). He can modify his routing table to see games on the VPN, but he won't be able to see both at the same time.

WinIPBroadcast is an extremely small program (15 KB executable) which has been specifically designed to solve this problem. It works using an interesting fact: it is possible to receive locally generated global broadcast packets when listening on the loopback address (127.0.0.1). WinIPBroadcast listens on the local address for all broadcast using RAW sockets, then for each broadcast packet, it relays it to all interfaces except the prefered one.

Thus, if an application send a broadcast packet, Windows will send it to the preferred interface, then WinIPBroadcast will receive it and resend it to all other interfaces. In the end the packet is sent on all network interfaces: problem solved.

WinIPBroadcast has been successfully tested on Windows 7 and Windows 10. Older Windows versions are unsupported.

WinIPBroadcast cannot "see" packets where the source and destination ports are identical. So, for example, if the application is sending packets to 255.255.255.255:42 from 1.2.3.4:42, WinIPBroadcast won't be able to relay them. This appears to be an inherent limitation of the "loopback address hack" described above. For this reason it is unlikely to ever be fixed. (One example of an application that falls into this category is Command & Conquer 3, which sends packets from port 8086 to port 8086.)

In theory, it should be possible to choose which network interface will be used by default by altering the metric of the global broadcast route. In pratice however, that approach seems to be very hit and miss, and some applications will completely ignore such changes.

In some versions of Windows, it is possible to choose which network interface will be used by default by changing the adapter order in the "Advanced Settings" accessible from a menu in the "Network Connections" folder. Unfortunately, that functionality seems to have been removed in Windows 10.

ForceBindIP can be used to force specific applications to bind to a specific network interface, thereby forcing them to send broadcast packets through that interface.

You just need to install it. WinIPBroadcast runs as a service which will be automatically started at the end of the installation. There is no configuration, It Just Works (TM).

To control WinIPBroadcast, use the Service Manager in the Administration Tools folder of the Control Panel.

You can use WinIPBroadcast on the command line using these parameters:

• WinIPBroadcast install installs the service.
• WinIPBroadcast remove removes the service.
• WinIPBroadcast run runs WinIPBroadcast as a console application. Useful for diagnostics (error messages will be shown).