[rednet] Would this work?

 
rednet.open("top")
rec = rednet.receive()

repeat
print(rec)
sleep(0.2)
until nil

would this work to print everything which gets broadcasted over rednet?

no
this is the wrong section to ask for help so think your self luckie i will help you. please send all further help questions to the ask a pro section.

the variable rec will not change so it will print the same thing every time

use this

rednet.open("top")
while true do
event, var1, var2 = os.pullEvent()
if event == nil then
write("event is nill")
else
write("event is ".. event)
end

if var1 == nil then
write(" var1 is nill")
else
write(" var1 is "..var1)
end

if var2 == nil then
write(" var2 is nil")
else
write(" var2 is "..var2)
end
end

Like BigSHinyToys said, this code won't work. However, with minimal effort you could make it work! :)/>/>

Instead of

rednet.open("top")
rec = rednet.receive()
repeat
print(rec)
sleep(0.2)
until nil

You could try

rednet.open("top")
while true do -- Continues until terminated by the user or event specified
sender, message = rednet.receive(1.3) -- The argument stated here is a timeout,
or how long the machine will be receiving for before it jumps to the next line of code. This timeout will act as our sleep()
-- Also, rednet,receive() in its most basic form returns two values:
the id of the computer which sent the message, and the message which is self explanatory.

term.clear()
term.setCursorPos(1,1) -- Just clearing the screen
if sender == nil then print("Sorry! I got nothing...")
else print("Sender: "..sender.."nMessage: "..message)
end