I wrote a "Discovery Service" for adhoc single segment networks that uses UPD broadcast. Every node runs the discovery service. Each nodes sends a "who" message on a timer. When a node recieves a "who" message, it resets it's timer and sends an "iam" message. Thus, only the node with the fastest timer actually sends a "who" message. If that node goes away, then the next fastest node will start sending the "who" command. Thus Nodes+1 messages are sent at each timer tick. Each node stores and ages the "iam" messages. Each node also serves a TCP port to allow direct queries of what the node knows. A local client can query the "localhost" TCP service to find the services and IP address available on the segment. There are also two utilities provided. One to manually query the "localhost" service and another to watch all UPD traffic. I also use this utility as a debug message viewer - I embed UDP send trace messages in programs I'm debugging.
The service is based on Indy 9.???. There are, I believe, some other components used that are available on the web. The code does not contain any copyright notices, that I remember, so use it as you will. It would be nice to know if you do use it. The code comes in a .zip of the directory that it resides in so it will tahe a little work to get it compiled. I use Delphi 7. This version runs as a service and contains some remnants of the application version that could be removed. The Application version, which has its own builtin viewer utility, still exists and could also be made available. If you want a copy, reply off list and I'll send you a link. If the Indy folks would like to use it as "example" code, It would have to be converted to Indy 10. Doug
