UDP Communication
Receiving UDP Data
To receive data from network via UDP, pid_recvfrom function is required.
There are two receive buffers of UDP and the following shows how they works.
※ Refer to Appendix for information about UDP receive buffer size depending on the types of products.
receiving UDP data from network
reading UDP data from receive buffer
After reading data from receive buffer by calling pid_recvfrom function, PHPoC flushes the buffer.
reading data size less than received data size
Remaining data after reading will be lost by flushing receive buffer.
losing data by no available receive buffer
While each of two receive buffers has data which have unread data, subsequent data from network cannot be received. Therefore, it is recommended to read data as soon as possible in received buffer right after checking received data size.
example
This example prints received UDP data, checking if there is data comes from network every second.
<?php
$rbuf = "";
$pid = pid_open("/mmap/udp0"); // open UDP 0
pid_bind($pid, "", 1470); // binding
while(1) // infinite loop
{
$rxlen = pid_ioctl($pid, "get rxlen"); // get received data size
if($rxlen)
{
pid_recvfrom($pid, $rbuf, $rxlen); // receive data
echo "$rbuf\r\n"; // print received data
}
usleep(100000);
}
?>Sending UDP Data
To send UDP data, pid_sendto function is required.
example of sending UDP data
<?php
$sdata = "01234567";
$pid = pid_open("/mmap/udp0"); // open UDP 0
$slen = pid_sendto($pid, $sdata, 8, 0, "10.1.0.2", 1470); // send data
echo "slen = $slen\r\n"; // print size of send data
pid_close($pid);
?>