Hi _avr_,
first of all, the TTL can only be specified for a sender (writing a message to the network), not for a listener (scanning a network).
As you have already noticed, the TTL can only be applied when using the UDP Multicast Write Open.vi (or Write/Read). So what for is the TTL terminal anyway?
You can compare the UDP protocol to a radio station (sender/broadcast) with multiple listeners (receivers). Every radio station specifies a certain range (TTL), how far the signal can be received from the radio tower. For UDP it's just the same. You specify how many routers the signal/message can cross (range of the signal within a network). The Listener/Receiver has to be in range of the TTL, so he can read the message.
Now let's have a look at Singlecast connections. A Singlecast connection needs a specified IP to write to the Listener (like making a telephon call >> telephon number). Therefore, there is no need to specify a TTL for the sender, because the connection to the listener has to be established first. So you have a fixed IP of a listener that your message is applied to.
When using Multicast you are writing to a Multicast address (something like a relay station) every listener can connect to. But these Listeners have to be in range of the sender (specified by the TTL).
If you still want to use the TTL, then you have to use Multicast. Specify a Multicast IP your message will be send to and then let a single Listener (not Singlecast) read the message from the respectiv Multicast IP.
I hope this is the answer to your question...
Daniel
NIG
