Making Things Talk

398 MAKING THINGS TALK

Chapter 7

Lantronix UDP Device Query

Language: Processing

Sends out a UDP broadcast packet to query a subnet for

Lantronix serial-to-ethernet devices. Lantronix devices

are programmed to respond to UDP messages received

on port 30718. If a Lantronix device receives the string

0x00 0x00 0x00 0xF6, it responds with a UDP packet

containing the status message on port 30718. When the

program starts, press any key on the keyboard and watch

the message pane for responses. See the Lantronix inte-

gration guide from www.lantronix.com for the details. This

program uses the Hypermedia UDP library available at

hypermedia.loeil.org/processing/

// import UDP library

import hypermedia.net.*;

UDP udp; // define the UDP object

int queryPort = 30718; // the port number for the device query

void setup() {

// create a new connection to listen for

// UDP datagrams on query port;

udp = new UDP(this, queryPort);

// listen for incoming packets:

udp.listen( true );

}

void draw() {

// twiddle your thumbs. Everything is event-generated.

}

/*

send the query message when any key is pressed:

*/

void keyPressed() {

byte[] queryMsg = new byte[4];

queryMsg[0] = 0x00;

queryMsg[1] = 0x00;

queryMsg[2] = 0x00;

// because 0xF6 (decimal value 246) is greater than 128

// you have to explicitly convert it to a byte:

queryMsg[3] = byte(0xF6);

// send th