UDP Receive
Receive UDP packet
Block Library
Embedded Coder/Embedded Targets/Host Communication
Description
The UDP Receive block receives UDP packets from an IP network port and saves them to its buffer. 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 C/C++ 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 these extra .dll files
when doing so. The packNGo function creates a
single zip file containing all of the
pieces required to run or rebuild this code. For more details, see How To Run a Generated Executable Outside MATLAB (DSP System Toolbox).
Parameters
- Local IP port
Specify the IP port number on which to receive UDP packets. This parameter is tunable in the C/C++ generated code but not tunable during simulation. The default is
25000. The value can be in the range [1, 65535].Note
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
- Remote IP address (
'0.0.0.0'to accept all) Specify the IP address from which to accept packets. Entering a specific IP address blocks UDP packets from other addresses. To accept packets from any IP address, enter
'0.0.0.0'. This value defaults to'0.0.0.0'.- Receive buffer size (bytes)
Make the receive buffer large enough to avoid data loss caused by buffer overflows. This value defaults to
8192.- Maximum length for Message
Specify the maximum length, in vector elements, of the data output vector. Set this parameter to a value equal or greater than the data size of a UDP packet. The system truncates data that exceeds this length. This value defaults to
255.If you disable Output variable-size signal, the block outputs a fixed-length output the same length as the Maximum length for Message.
- Data type for Message
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.- Message is complex
Select this parameter to receive the message as complex data. Clear this parameter if the received message is real. By default, this parameter is not selected.
- Output variable-size signal
If your model supports signals of varying length, enable the Output variable-size signal parameter. This checkbox defaults to selected (enabled). 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, disable the Output variable-size signal parameter. In that case:
The block emits a fixed-length output the same length as the 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.
The block dialog box displays the Data type for Length parameter.
In both cases, the block truncates data that exceeds the Maximum length for Message.
- Blocking time (seconds)
For each sample, wait this length of time for a UDP packet before returning control to the scheduler. This value defaults to
inf, which indicates to wait indefinitely.Note
This parameter appears only in the Embedded Coder® UDP Receive block.
- Sample time (seconds)
Specify how often the scheduler runs this block. Enter a value greater than zero. In real-time operation, setting this option to a smaller value reduces the likelihood of dropped UDP messages. This value defaults to a sample time of 0.01 s.
Deprecated Parameters
- Output port width
Specify the width of packets the block accepts. When you design the transmit end of the UDP communication channel, you decide the packet width. Set this option to a value as large or larger than a packet you expect to receive.
Note
This parameter appears only in a deprecated version of the UDP Receive block. Replace the deprecated UDP Receive block with a current UDP Receive block.
- UDP receive buffer size (bytes)
Specify the size of the buffer to which the system stores UDP packets. The default size is 8192 bytes. Make the buffer large enough to store UDP packets that come in while your process reads a packet from the buffer or performs other tasks. Specifying the buffer size prevents the receive buffer from overflowing.
Note
This parameter appears only in a deprecated version of the UDP Receive block. Replace the deprecated UDP Receive block with a current UDP Receive block.