help with rednet

I need some help with my code. I'm not sure what's wrong it tells me expected positive number, I'm tyring to send a message to my turtle and if the message is str it will move forward here's the code for the sending computer
–send

write ("which side is your modem:")
ms = io.read()
rednet.open(ms)
write ("id of turtle:")
idt = io.read()
idt = tonumber(idt)

while true do
event, param1 = os.pullEvent()
if param1 == "w" then
rednet.send("str", idt)
end
end

And here's the code for the receiving turtle
–receive

write ("which side is your modem:")
ms = io.read()
rednet.open(ms)
while true do
Id, message = rednet.receive()
if id == "str" then
turtle.forward()
end
end

Please could any1 help , this is hopefully going to be remote control program thanks.
Any help will be appreciated

You've got the arguments swapped in your rednet.send. Should be ID THEN message.

You also need to then check message instead of id in the receiving program.

I tried that it still says positive number expected!but thanks for your reply

Never got it to work thanks a lot !

Never mind I meant

I think I know what the problem is.

You send a string what needs to be an Int.

This can simple be solved with this code :
tonumber([string]) and the output will be in int format, and ready for use.

Also :

if param1 == "w" then
rednet.send("str", idt)
end

Needs to be

if param1 == "w" then
rednet.send(15[The computerID, not the message], "str"[Here needs to be the message])
end

Also have a look at this :

while true do
Id, message = rednet.receive()
if id == "str" then
turtle.forward()
end

Needs to be :

while true do
Id, message = rednet.receive(1[A timeout is always nice])
if message == "str" then
turtle.forward()
end

this can be changed in multply places in your code.

If you have more question, just send a message to me, and I will be glad to help.

Also, you don't have to ask on which side the modem is on the turtle, it's always on the right side.