This week's giveaway is in the Android forum.
We're giving away four copies of Android Security Essentials Live Lessons and have Godfrey Nolan on-line!
See this thread for details.
The moose likes Other JSE/JEE APIs and the fly likes serial port problems Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login

Win a copy of Android Security Essentials Live Lessons this week in the Android forum!
JavaRanch » Java Forums » Java » Other JSE/JEE APIs
Bookmark "serial port problems" Watch "serial port problems" New topic

serial port problems

Ellen Murphy

Joined: Nov 17, 2004
Posts: 2
Hi, ive only just started programming in java. My FYP involves getting gps info over serial port and searching the data rxed for time etc. I've managed to get SImpleRead working for the GPS im using so it reads everything in fine. I have to search through the sentences (input) received now for the word $GPRMC and im having great difficulty. i cant see exactly what is my input in the code, is it inputStream or buffer??? can anyone help heres my code so far

import java.util.*;
import javax.comm.*;

public class SerialRead implements Runnable, SerialPortEventListener {
static CommPortIdentifier portId;
static Enumeration portList;

InputStream inputStream;
SerialPort serialPort;
Thread readThread;
boolean portOpen;
BufferedInputStream in;

public static void main(String[] args) {
portList = CommPortIdentifier.getPortIdentifiers();

while (portList.hasMoreElements()) {
portId = (CommPortIdentifier) portList.nextElement();
if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
if (portId.getName().equals("COM1")) {
System.out.println("Found Serial Port!!!");
SerialRead reader = new SerialRead();

public SerialRead() {
System.out.println("Opening Serial......");
try {
serialPort = (SerialPort)"SimpleReadApp", 2000);
portOpen = true;
} catch (PortInUseException e) {}
try {
System.out.println("Getting input stream....");
inputStream = serialPort.getInputStream();
in = new BufferedInputStream(inputStream, 1024);
} catch (IOException e) {
System.out.println("Error opening i/o streams");}
try {
} catch (TooManyListenersException e) {}
try {
} catch (UnsupportedCommOperationException e) {}

System.out.println("Parameters set");
readThread = new Thread(this);

public void run() {
try {
} catch (InterruptedException e) {}

public void serialEvent(SerialPortEvent event) {
// Create a StringBuffer and int to receive input data.
StringBuffer inputBuffer = new StringBuffer();
int newData = 0;

//Determine type of event
switch(event.getEventType()) {
case SerialPortEvent.BI:
System.out.println("\n--- BREAK RECEIVED ---\n");
case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
case SerialPortEvent.DATA_AVAILABLE:
while (newData != -1) {
try {
newData =;
if (newData == -1){
if('\r' == (char)newData) {
} else{

System.out.print(new String(inputBuffer));
} catch (IOException ex) {

// //Method to find GPRMC in buffer
// public void GetGPRMC()
// {
// int counter = 0;
// do{
// //search the i/p buffer to find GPRMC word
// if(inputBuffer.regionMatches(counter, GPRMC, 0, 5)){
// //store 127 characters starting at GPRMC
// String temp = inputBuffer.substring(counter, counter + 127);
// counter = 0;
// //Tokenize string with respect to commas
// StringTokenizer tokens = new StringTokenizer(temp, ",");
// while(tokens.hasMoreTokens() && (counter < 11))
// {
// gpsData[counter] = tokens.nextToken();
// }
// }
// }
// }

//Close connection method
public void CloseConnection()
if (!portOpen)
return; // if the port is already closed, do nothing
try {
inputStream.close(); //close inputstream
catch (IOException e) {

serialPort.close(); // close port


i know its not an incredibly difficult thing to do but ive been puzzling over it for a while now and still cant see how to go about it. i know i could use regionMatches method but i dont know which string to use to call it.....

confused laela
Ernest Friedman-Hill
author and iconoclast

Joined: Jul 08, 2003
Posts: 24183

We like to put questions about the JavaComm API in our Other Java APIs forum. I'll move this over there for you and maybe you'll get a nibble.

[Jess in Action][AskingGoodQuestions]
It is sorta covered in the JavaRanch Style Guide.
subject: serial port problems
Similar Threads
Code of SMS application
Send SMS by using Serial Port
Converting data file to text file
how can I send the output of a servlet to a jsp page?
serial port problems