The Java Communications API (also known as javax.comm) provides applications access to RS-232 hardware (serial ports) and limited access to IEEE-1284 (parallel ports), SPP mode.
How To use javax.comm
This package contains following files.
1. comm.jar
2. win32com.dll
3. javax.comm.properties
Place the above files in below location.
comm.jar should be placed in:
%JAVA_HOME%/lib
%JAVA_HOME%/jre/lib/ext
win32com.dll should be placed in:
%JAVA_HOME%/bin
%JAVA_HOME%/jre/bin
%windir%System32
javax.comm.properties should be placed in:
%JAVA_HOME%/lib
%JAVA_HOME%/jre/lib
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How to Read data from Serial Port
import java.io.*;
import java.util.*;
import javax.comm.*;
public class ReadData implements Runnable, SerialPortEventListener {
static CommPortIdentifier portId;
static Enumeration portList;
InputStream inputStream;
SerialPort serialPort;
Thread readThread;
public static void main(String[] args) {
boolean portFound = false;
String defaultPort = "/dev/term/a";
if (args.length > 0) {
defaultPort = args[0];
}
portList = CommPortIdentifier.getPortIdentifiers();
while (portList.hasMoreElements()) {
portId = (CommPortIdentifier) portList.nextElement();
if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
if (portId.getName().equals(defaultPort)) {
System.out.println("Found port: "+defaultPort);
portFound = true;
ReadData reader = new ReadData();
}
}
}
if (!portFound) {
System.out.println("port " + defaultPort + " not found.");
}
}
public ReadData() {
try {
serialPort = (SerialPort) portId.open("ReadApp", 2000);
} catch (PortInUseException e) {}
try {
inputStream = serialPort.getInputStream();
} catch (IOException e) {}
try {
serialPort.addEventListener(this);
} catch (TooManyListenersException e) {}
serialPort.notifyOnDataAvailable(true);
try {
serialPort.setSerialPortParams(9600, SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
} catch (UnsupportedCommOperationException e) {}
readThread = new Thread(this);
readThread.start();
}
public void run() {
try {
Thread.sleep(20000);
} catch (InterruptedException e) {}
}
public void serialEvent(SerialPortEvent event) {
switch (event.getEventType()) {
case SerialPortEvent.BI:
case SerialPortEvent.OE:
case SerialPortEvent.FE:
case SerialPortEvent.PE:
case SerialPortEvent.CD:
case SerialPortEvent.CTS:
case SerialPortEvent.DSR:
case SerialPortEvent.RI:
case SerialPortEvent.OUTPUT_BUFFER_EMPTY:
break;
case SerialPortEvent.DATA_AVAILABLE:
byte[] readBuffer = new byte[20];
try {
while (inputStream.available() > 0) {
int numBytes = inputStream.read(readBuffer);
}
System.out.print(new String(readBuffer));
} catch (IOException e) {}
break;
}
}
}
How to write data to serial port
import java.io.*;
import java.util.*;
import javax.comm.*;
public class WriteData {
static Enumeration portList;
static CommPortIdentifier portId;
static String messageString = "Hello, world!";
static SerialPort serialPort;
static OutputStream outputStream;
static boolean outputBufferEmptyFlag = false;
public static void main(String[] args) {
boolean portFound = false;
String defaultPort = "/dev/term/a";
if (args.length > 0) {
defaultPort = args[0];
}
portList = CommPortIdentifier.getPortIdentifiers();
while (portList.hasMoreElements()) {
portId = (CommPortIdentifier) portList.nextElement();
if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
if (portId.getName().equals(defaultPort)) {
System.out.println("Found port " + defaultPort);
portFound = true;
try {
serialPort =
(SerialPort) portId.open("WriteData
", 2000);
} catch (PortInUseException e) {
System.out.println("Port in use.");
continue;
}
try {
outputStream = serialPort.getOutputStream();
} catch (IOException e) {}
try {
serialPort.setSerialPortParams(9600,
SerialPort.DATABITS_8,
SerialPort.STOPBITS_1,
SerialPort.PARITY_NONE);
} catch (UnsupportedCommOperationException e) {}
try {
serialPort.notifyOnOutputEmpty(true);
} catch (Exception e) {
System.out.println("Error setting event notification");
System.out.println(e.toString());
System.exit(-1);
}
System.out.println(
"Writing \""+messageString+"\" to "
+serialPort.getName());
try {
outputStream.write(messageString.getBytes());
} catch (IOException e) {}
try {
Thread.sleep(2000); // Be sure data is xferred before closing
} catch (Exception e) {}
serialPort.close();
System.exit(1);
}
}
}
if (!portFound) {
System.out.println("port " + defaultPort + " not found.");
}
}
}
