UDP Receive

Receive UDP message from UDP host

  • Library:
  • Simulink Coder Support Package for NXP FRDM-K64F Board

Description

The UDP Receive block receives UDP message from a UDP host.

With each sample, the block outputs the data bytes of a UDP message as a data vector of the size that you specify in the Data size (N) parameter.

The block receives the message on the port number specified in the Local IP Port parameter. Match the port number specified in the Local IP Port parameter with the remote port number of the sending host.

You can choose to receive the UDP message in blocking or non-blocking mode.

Note

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

Ports

Output

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At each sample time, the port outputs the data bytes of a message received as a data vector of the size that you specify in the Data size (N) parameter. For more information, see Receive UDP messages.

Data Types: int8 | uint8 | int16 | uint16 | int32 | uint32 | single | double | Boolean

At each sample time, the port outputs the number of data bytes in the received message. For more information, see Receive UDP messages.

Data Types: uint16

Parameters

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Specify the port number of the application on which you want to receive the message. Match the local port number with the remote port number of the sending host.

Select the data type in which the block receives the data bytes from the sending host.

Specify the number of data bytes that you want to receive in each message.

  • on — When you select this parameter, the read operation runs in the Blocking mode. The read operation is blocked while waiting for the requested data to be available. If data is available, the Data port outputs data. If data is not available, the Data port waits for data. While the block waits for new data to arrive, the Size port outputs 0. When the new data arrives, the value at the Size port changes to a nonzero value.

    A task overrun occurs if the target hardware is still waiting for the data to be available when the next read operation is scheduled to begin.

    To fix overruns:

    • Increase the time step by using the Sample time parameter.

    • Reduce the length of data requested by using the Data size (N) parameter.

  • off — When you clear this parameter, the read operation runs in the Non-blocking mode. When reading data, if data is not available, the Data port contains the message it received in the previous time step. The Size port outputs 0. In this mode, the block does not wait for the requested data to be available.

When you specify this parameter as-1, Simulink® determines the best sample time for the block based on the block context within the model.

Receive UDP messages

This example describes the values at the output ports when the length of the messages received is less than, greater than, or equal to the length of requested data. This section explains the values at the output ports, with Data type set to uint8 and Data size (N) set to 4.

  • Length of UDP message received = Data size (N): The Data port outputs the message as a data vector of the size specified in the Data size (N) parameter.

    The Size port outputs the number of data bytes received.

    Suppose that the Data size (N) parameter specified is 4 and the length of the message received is also 4.

    In this case, the Data port outputs a data vector of size 4 filled with the data bytes of the message.

    The value at the Size port is 4.

  • Length of UDP message received < Data size (N): The Data port outputs the message as a data vector of the size specified in the Data size (N) parameter. All the empty spaces in the vector are filled with random values.

    The Size port outputs the number of data bytes received (excluding random values).

    Suppose that the Data size (N) parameter specified is 4 and the length of data received is 3 bytes.

    In this case, the Data port outputs a data vector of size 4. The first three data bytes in the vector are the bytes from the received message. The remaining space is filled with a random value.

    The value at the Size port is 3.

  • Length of UDP message received > Data size (N): The Data port outputs a data vector of the size specified in the Data size (N) parameter. The vector contains only the first N data bytes from the message. The remaining data bytes are dropped.

    The Size port outputs the number of data bytes received (including the output data bytes and the dropped data bytes).

    Suppose that the Data size (N) parameter specified is 4 and the length of data received is 5 bytes. In this case, the Data port outputs a data vector of size 4. The vector contains only the first four data bytes from the received message. The remaining data byte is dropped. The value at the Size port is 4+1=5.

Introduced in R2017a