Problem solved by using this code. Apparently one has to close the socket after sending and open a new one for receiving. It seams to be a unique behaviour of this device (server):
$socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); $bytes = socket_sendto($socket, $message, strlen($message), 0, "192.168.0.37", 7090); socket_close($socket); $message="curr 7700"; $socket = socket_create(AF_INET, SOCK_DGRAM, SOL_UDP); socket_bind($socket, '0.0.0.0', 7090); $from = ''; $port = 0; socket_recvfrom($socket, $buf, 512, 0, $from, $port); echo $buf . PHP_EOL;
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