[Rednet question] Checking if ID exists?

tMsgs = {
["PCFound"] = "Connected to PC with ID: ",
["PCNotFound"] = "Unable to connect to PC with ID: ",
}


function cls(x,y)
    term.clear()
    term.setCursorPos(x,y)
end

rednet.open("top")

while true do
    repeat
        cls(1,1)
        write("Enter the ID of the computer you would like to interact with: ")
        cID = tonumber(read())
    until type(cID) == "number"
    print("\nAttemping to connect to PC with ID: "..cID)
    sleep(3)
    rednet.send(cID,"test")
    os.startTimer(0.1)
    event, sID, msg, dist = os.pullEvent()
    cls(1,1)
    if event == "timer" then
        print(tMsgs["PCNotFound"]..cID)
    elseif event == "rednet_message" then
        if msg == "true" then
            print(tMsgs["PCFound"]..cID)
        end
    else print("Event: "..event)
    end
    sleep(3)
end

function cls(x,y)
    term.clear()
    term.setCursorPos(x,y)
end

rednet.open("top")

while true do
    cls(1,1)
    print("Waiting for a rednet message...")
    event, rID, msg, dist = os.pullEvent("rednet_message")
    if msg == "test" then
        cls(1,1) print("Received message: "..msg.."\nSending message: true to PC with ID: "..rID)
        rednet.send(rID, "true")
    end
end