Messenger or Texting tool for dispatchers

I'm looking for a messenger or texting tool between PCs.
There will be a main station which can send text to an individual or a group.
And there will be a group who receives it and can send or reply ONLY to the main station, but among the group, they can not recognize each other, nor can send or reply.

There are many messengers and chat tool, but they all allow a group chat which doesn't fit to dispatching senario.

After I wrote down, basically what I want to find is, some very simple texting tool which can be used for bidding.
There are multiple stations with the software installed, they will standby and receive a message from the main station, and they reply with 'T' or simple text showing interest. Then, the main station continues the first bidder with message.
It should be simple so that only messaging and/or file exchange are the only need
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LanTalk NET is exactly what you need. All clients can be in Reply-only mode and the main station in the full client mode:
You download trial version here:

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