How do I get a text on client application running on a network in VB.NET

All very interesting. But the issue remains the same: you need a client application that will send this status information to your server.

Google for "sockets vb.net" and you will find plenty of samples.

This message was not meant for me.

1. Use TCP
2. Create a simple protocol to allow each end to communicate in the same way

If I understand you Question, you are working on a peer to peer chat. A centralized system would be easier, however, the way to do this, would be to add, (I have mine prior) a message type code to your data string between clients.
EXAMPLE: if you are current using something like TCP.send("chat message") you would have to add a routine to add and inspect on arrival a code.
dim MSG as string = "Chat Message"
DIM TYP as string = "1"= chat message --- "2" = status request --- 21 = status availible -- 22 = status do not disturb
On a status request, the MSG could be "" on both the request and response.

Dim Payload as string = TYP + "|" + MSG
TCP.SEND (PAYLOAD)

Assign the incoming data to an array using split
check the TYP if status request send back code for current status
if chat message display in local client
The values I have used are only examples, it can be coded with letters or any numbers you want. As long as each client understands all the codes to send and recieve (and what to do with them.
So when a user enters an IP address, the system would send the status request code and receive back the current status.
Using a centralized server (any pc would do) you could have it do real time status.
For the communication I use, I based it on the Winsock_Orcas (available on this site)
There is a good chat server and client example with it, only need to build out the status codeing.

Let me know if you need further clarification.