UDP Read Receives Multiple Messages During UDP Broadcast

Issue Details

When using UDP broadcasting in LabVIEW, the UDP Read VI receives multiple messages for each individual broadcast message sent.

Solution

This can happen when a machine has multiple network cards. When a UDP message is broadcast, each network card will pick up the message. Since each network card gets the message, a LabVIEW program might receive multiple UDP broadcast messages for every one message sent. This can be common on laptops since they often have multiple network cards, both an Ethernet card and a wireless card.

To avoid this problem wire a network address to the input of the UDP Open VI. When the net address input of the UDP Open is not wired, LabVIEW will listen on all network addresses. If an address is specified, only that network card will be used. 

The String to IP primitive can be used to return the IP address from a machine. To see the multiple IP addresses available for a machine, right click on the String to IP primitive and select Multiple Output.