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UDP Receive

Receive UDP packets on a given IP port

  • UDP Receive block

DSP System Toolbox / Sources


The UDP Receive block receives UDP packets from an IP network port and saves them to its buffer. Due to the nature of the UDP transmission protocol, the receiver is not guaranteed to receive all the data packets that you send using the UDP Send block. With each sample, the block outputs the contents of a single UDP packet as a data vector.

The local IP port number on which the block receives the UDP packets is tunable in the generated code. The generated code for this block relies on prebuilt .dll files. You can run this code outside the MATLAB® environment or redeploy it, but you must account for the extra .dll files. The packNGo function creates a ZIP file that contains the pieces required to run or rebuild this code. For more details, see How To Run a Generated Executable Outside MATLAB.



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Data received by the UDP Receive block, returned as a one-dimensional vector of the data type specified in Data type for Message. If you select Message is complex, the block treats the received message as complex data.

If the packet gets dropped during transmission and the receiver does not receive the packet, the data received output is empty.

This port is unnamed until you clear the Output variable-size signal parameter.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean
Complex Number Support: Yes

Length of the data packet received, returned as a scalar. This value is determined by the value of the Maximum length for Message parameter.


This port appears only when you clear the Output variable-size signal parameter.

Data Types: uint16


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Specify the IP port number on which to receive UDP packets. This parameter is tunable in the generated code but is not tunable during simulation.

On Linux®, to set the IP port number below 1024, run MATLAB with root privileges. For example, at the Linux command line, enter sudo matlab.

Specify the IP address from which to accept UDP packets. Specify a specific IP address to block UDP packets from other addresses. To accept packets from any IP address, specify ''.

Specify the size of the buffer, in bytes, that receives the UDP packets. Make the buffer large enough to avoid data loss caused by buffer overflows.

Specify the maximum length, in vector elements, of the data output vector. Set this parameter to a value equal to or greater than the data size of a UDP packet. The system truncates data that exceeds this length.

If you disable Output variable-size signal, the block output is the length specified by this parameter.

Specify the data type of the vector elements in the message output. Match the data type to the data input used to create the UDP packets.

Specify whether the block receives a message as complex data. Select this parameter to receive a message as complex data. Clear this parameter if a received message is real data.

Specify whether your model supports signals of varying length. If your model supports signals of varying length, select this parameter. In that case:

  • The output vector varies in length, depending on the amount of data in the UDP packet.

  • The block emits the data vector from a single unlabeled output.

If your model does not support signals of varying length, clear this parameter. In that case:

  • The block emits a fixed-length output that is the same length as specified by Maximum length for Message.

  • If the UDP packet contains less data than the fixed-length output, the difference contains invalid data.

  • The block emits the data vector from the Message output.

  • The block emits the length of the valid data from the Length output.

If you disable this parameter, the block emits output that is the length specified by Maximum length for Message.

Specify the frequency at which the scheduler calls the UDP Receive block, in seconds. Enter a value greater than zero. In real-time operation, setting this parameter to a smaller value reduces the likelihood of dropped UDP messages.

Block Characteristics

Data Types

Boolean | double | integer | single

Direct Feedthrough


Multidimensional Signals


Variable-Size Signals


Zero-Crossing Detection


Extended Capabilities

Version History

Introduced in R2010a