UDP Receive

Receive UDP packets over IP network

Description

Receive UDP packets from the local network. The block output, data, emits UDP packet data as a one-dimensional vector of a specified data type. The block output, size, emits the size the data in the UDP buffer.

The data type of the block output, Data, depends on the Data type parameter. The data type of the block output, Size, is uint16.

While UDP Receive waits for new data to arrive, size emits a stream of zeros. When new data arrives, size changes to a non-zero value.

If you simulate a model that contains the UDP Receive block on your host computer (e.g., Simulation > Normal), and send UDP packets to that model from a board, the data output emits a disproportionately large number of zeros. This is because Simulink software simulates the model as a free-running application with a shorter period than the real-time application running on the board. In other words, the free-running simulation outputs zeros because it is waiting for the “slower” real-time application on the board to send data. If both applications were running on boards, this mismatch would not occur.

Note

If you are having trouble using UDP to communicate with a computer, investigate whether antivirus or firewall software might be blocking UDP traffic. If so, try configuring the software to allow UDP traffic for a specific IP port number.

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Parameters

Local IP port

The number of the IP port on the local device, which can range from 1 to 65535. This value defaults to 25000. The “local device” is the board running the model.

Data type

Set the data type of the vector elements in the Message output. Match the data type with the data input used to create the UDP packets. This option defaults to uint8.

Data size (elements)

Set the number of data elements in each UDP packet. Match the data size used to create the UDP packets. This value defaults to 255 elements.

Sample time (seconds)

Specify how often this block reads the port buffer. Enter a value greater than zero. This value defaults to a sample time of 0.01 seconds.

Smaller values require the processor to complete the same number of instructions in less time, which can cause task overruns.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.