Shell Programming and Scripting

Hello people,
which options do I have to send messages over a network from one station to another without using standard network messaging commands like write, talk und message? Thanks.

I suppose it depends on what you call sending a message. email works for most of us. You can ssh between hosts, but to message people youu need to find specific tty names as well. If you want them to reply, you need some sort of artifact there for them to send through. I once tried something with mmap() atached NFS files, but changes were not picked up unless I did an ls on the end remote from the write. Maybe if everyone tailed a file and wrote to that file under an id header line in tight blocks, you would have a logged chat session. I have done that. If you have no NFS, you can "ssh ... tail -f chatfile &" to see the dialog on one xterm and do an ssh to write blocks from another. You write blocks by composing them in an env variable and then echoing the variable as one atomic write. Oh, I said that word, but the command is echo not write.

Thanks. Well, I thought of a primitive SMS-like messaging function that allows to send messages either to one user or to a group of users. I thought I could use nc for that task, but I don't know if it's a good option.

What would would you recommend to simulate a network? Is it better to use multiple IP aliases on one physical host or to use multiple VMs?

If you want it to be utterly open, you might write something using UDP on a fixed high port and broadcast messages. It works to run at least one big name stock exchange. I suppose you might want some authentication so you know who you are talking to, and that means a server daemon or some peer equivalent.

I think I am going to simulate a network with VirtualBox, because here I have arbitrary amount of independent OSs.

The shell script should work like this:
1. The user logs in. Depending on his privileges, he can send messages to one user or to a group of users.
2. The receiver gets the message. If he is not online, the sender gets an error message.
The whole script shouldn't be based on P2P.

I am still unsure on which core commands this script should be build.

Some sort of JAVA or PERL app would be very portable and consistent across O/S.

I'm not allowed to use any other language than Linux Shell Script. In my opinion, rcp or nc are the only commands that could be used for network messaging.