Gustav Brock
Gustav at cactus.dk
Mon Jun 29 13:34:34 CDT 2009
Hi John As explained in the article on how to create a kind of confirmation system, you could set up a simple two-way system with a single syslog app broadcasting at low frequency "Here I am, and if you are an app from JC, record my address and report back". Your app, when running at the user, would pick up that message and send back a message for the syslog app to collect the addresses of currently running application copies. When a user signs off, after a time-out the syslog app realizes that this copy is off and removes it from the list. Thus, a current list of active applications can be maintained and they can communicate for whatever reason you decide. Note that communication between machines can really be done in many ways, it is just that syslog is an established standard for simple text messages of about 1K, and if that fits, why reinvent the wheel? /gustav >>> jwcolby at colbyconsulting.com 29-06-2009 20:05 >>> Gustav, As I mentioned, I have been looking for something like this for years, however everyone has to have a list of IPs that can be used with it to make it useful. I suppose I could kind of bootstrap this thing. The server address could be found by manual observation, then logged in a table along with the machine name. Each application FE instance looks and sends a message that it is logged in. The RECEIVER grabs the IP address and looks it up in the table. If not there it stores the IP in the table. Of course then the machine name has to be included in the message. I suppose that I could develop a message library, such that every time an application it fires a LOGIN message to everyone already in the table. The login message has a machine name as the data and apparently this widget automatically gets the IP address. My clients rarely have more than 25 or so workstations running the application so this shouldn't cause too much grief. Thus anyone listening logs the new person's data into the table if it isn't already there. Kind of crude but that allows any single running application (that you can manually get the IP for) to bootstrap the system and build the list of IPs and machine names. John W. Colby www.ColbyConsulting.com Gustav Brock wrote: > Hi John > > Well, you have to decide. If you wish to communicate, either the sender or the receiver has to identify itself. That drives anything on the Internet. > > And syslog is not broadcasting. If you wish to listen to any address on your local network or transmit to any address on the local network, you have to determine the address of your machine and the subnet mask and you can calculate all possible addresses. Note that network admins hate broadcasting applications as these are considered noisy. > If you wish to communicate in or out of your local network, again you must know "something" about the machine(s) out there and your router will take care of the rest (if it and the firewall allows). > > The reason Hamachi and the like works is because they initially use port 80 (which can be considered open on any office network) and an external proxy to establish communication - so sender and receiver can identify each other. Nothing black magic here. > > syslog is fun because it is so primitive. This makes it an universal tool with heavy limitations but with nearly zero use of resources. What has been missing is prebuilt methods to read and write the messages from/to a database - to make it useful for people like us. This is what and how the article describes. > > /gustav _______________________________________________ dba-VB mailing list dba-VB at databaseadvisors.com http://databaseadvisors.com/mailman/listinfo/dba-vb http://www.databaseadvisors.com