IT & INTERNET - [Network watcher]
If you are using a Local Area Network at home, it would be nice to see which computers are running and which are not.
In a network with only 2 computers isn't that a problem: when one of the computers is off, a "disconnected icon" appears in the system tray of the other computer. If you are using a network with more than 2 computers, using a HUB or a ROUTER, you can see the state of each computer on the ROUTER/HUB itself (since the state is indicated by LEDs). But not everyone has physical access to the hubs, so there must be another way.
I have designed network watcher as a software solution to this problem. It keeps a list of all computers that are running on your home network. If a computer comes online, it will be added in the list. If a computer goes offline, it is removed from the list.
Network watcher keeps a list of all computers that are running on the network. For this, you are required to install network watcher on each of these computers.
One installed and running, each Network Watcher sends a message to all other network watchers on a regular base (using broadcasting). The broadcast message includes the computer name of the broadcaster. With this message, each Network Watcher lets the other watchers know "hey, I'm still online".
When the other network watchers receive the message, they know the source of the broadcast (since this information was included in the message). Then, they check if they already have a record on that specific origin. If there is no record, one is made. If there already is a record from that origin, the timestamp is updated. A record has the following 2 items:
On a regular base, each record is checked and the difference between the current time and the Timestamp value is measured. If this difference is greater than a predefined value (60seconds), network watcher assumes that that computer is offline, and removes the record from memory.
The system doesn't need any centralized components, which means there is no single-point-of-failure. A disadvantage could be the required network traffic, especially in huge networks (With hundreds of computers). But this application was designed for a LAN, with only a few computers. Although, the sent information is limited to the name of the computers only (very little data traffic). You also need a network with UDP/IP support to make this application work.
This application is written in Visual Basic 5.0. You can get the setup application (zipped,2.2MB).