Something to send messages to other PC's over LAN

[EOC2611P]

Hi,
i was looking for something to let me send messages to other computers connected to my wi-fi internet connection.
I tried some softwares i found on the internet (LanSend, and 3-4 others i can't remember the names), some of which were almost 10 years old, but i disinstalled them almost immediately after testing as none of them were working…
I also downloaded a PfSense package named "Avahi", as the description of it was just what i needed, but there was no GUI or any guide i could use on how to make it work!!
So, in short, anything that can show a message like "Sorry guys, the wi-fi is going to be switched off in a few minutes, please save your work before is too late", on pc's on my wireless lan without the need to phisically install a software on the other machines, even if i am giving out my connection for free, i find kind of rude to just switch it off without warning but i also don't want to be tied up to some pre-established schedule,
Thank you so much for any help/suggestion.

I am using Windows XP on the local server(with Xampp 1.7.4) and the latest version of PfSense installed on the hardrive of another pc.

[stephenw10]

The problem you have here is that the client computers have to be running some software that is listening for the messages and will then display them to the user, rather than just logging them for example.
It's likely that your clients may be running such software included within the OS. However you will probably need to address each OS specifically. For instance you can use netsend for Windows clients (though I've only tried to use it up to WinXP) and there may well be a port for FreeBSD but that's not going to work for Mac or Ubuntu users (or phone, tablet, games console users!).

Steve

[matguy]

The Messaging services that respond to Net Send have been disabled by default in most OSs these days due to messaging SPAM (deliberate or as a symptom of an infected machine on the network.)

These services can be enabled or installed, but you'll have to have administrative control over the end user machines.

I can't think of a good way to send messages to end client machines without also disrupting their network usage (such as using a captive portal and kicking everyone to a login page with messages), but I would presume that would kind of defeat your goal of warning them before they get kicked.  The main reason those tools don't usually exist by default is because they can be abused, as we used to see with Net Send and the Messaging service (you used to get barraged with messages that would pop to the front of your screen, it was bad.)

[johnpoz]

As mentioned there is not really a way to do this, because of the security issues - MS learned their lesson the hard way back quite a few years with messenger running out of the box with no way to filter who could send messages, etc.

I would prob look to growl, runs on mac, windows and linux/bsd so should cover your bases for any sort of connected OS.  But your going to have to setup up the system before hand on the machines.

Growl is a very robust notification system that could do exactly what you want, and no cost other than setup.

[EOC2611P]

Right, thanks for all the inputs.
I am sure i did try NetSend too, to the best of their performance, i could only see my own pc in the list of the available machines, none at all with the other softwares, so, nevermind….
I like the suggestion about sending them back to the Captive Portal's page, but the problem is, that all people having access to the net, have been added to a list to pass-through the CP by MAC Address, and i see no option on the interface to take off this privilege for all of them at once, only one by one.
An alternative would be changing the system to make them register first, but i didn't try this system yet, and i am not sure if 1) Every user can have a permanent password/username and 2) They can eventually be diverted to the CP's page all at once, or will i incur to the same problem with the MAC Addresses, having to check one by one???
All of the computers/notebook around here, are running on Windows...i get every now and then some mobile devices.
There is really no-one here that installed this Avahi and knows if i can do what i need with it???
It's really one of those "magical mistery packages"... :D
I will let you know on what new solution i will implement, if any.
Now i am going to put some new rants on a CMS forum

[stephenw10]

Avahi doesn't provide any sort of messaging service. It allows Macs on your network to discover each other such that if they are running a messaging service they can easily see a list of all available recipients.

http://doc.pfsense.org/index.php/Avahi_package

There must be plenty of other people who have come across this problem and solved it in various ways. A common solution to this in public networks is small pop-up window that comes from the captive portal. This can stay open and commonly shows you connection time or how much you're being charged. You could have this follow a url with local information.

Steve

[EOC2611P]

Yes a popup's window will do, even one of those horrible DOS little black windows as long as the message can be understood, but how to pass it to the other machines? especially when i can not put my hands on them…
A workaround would be asking everyone to be added on their friend's list of a chatting program but that looks so "intruding" and definetely not a professional touch..

[matguy]

I say to go Low-Fi and get a bull horn to announce it loudly.

[EOC2611P]

@matguy:

I say to go Low-Fi and get a bull horn to announce it loudly.

I might end up with a few dozen strays at my door waiting to start a fox's chase with this system…..
However, these kind of approach might even resolve a long standing problem i had with my firewall, as some buckets full of water can ensure a pass through better than any sophisticated rules, with a bang  :D