Receiving data of RS-232C device using java

Question

I have recently purchased a USB Bar code scanner. It has 3 different interface selection options:

1. RS-232C
2. USB
3. Wand Emulation

The requirement is only to receive the scanned bar-code using RS-232C interface with the help of Java (Rxtx API). So as far as I know, I will need a COM Port to be defined in RXTX to start interaction with the device

But the problem is I am not able to find out its COM Port while using in RS-232C interface.

Is there anything that I am missing while communicating a RS-232C port, How can I find the port number.

Please help me in this.

Update: As suggested I scanned my system for all the serial ports using the code below(using JSSC)

 import jssc.SerialPortList;

public class Main {

public static void main(String[] args) {
    String[] portNames = SerialPortList.getPortNames();
    for(int i = 0; i < portNames.length; i++){
        System.out.println(portNames[i]);
    }
}
}

One thing to note: when I connect my barcode scanner and remove the scanner, there is no change in the port list obtained by the above code.

Output: COM3 COM11 COM18 COM32 COM33 COM34 COM35 COM36 COM37 COM38 COM39 COM40 COM42 COM45 COM52 COM53 COM59 COM60 COM61 COM62 COM63

After the output I tried to listen each of the above port one by one using the following code:

import jssc.SerialPort; import jssc.SerialPortException;

public class Main {

public static void main(String[] args) {
    SerialPort serialPort = new SerialPort("COM63"); //manually setting all the ports above one by one
    try {
        serialPort.openPort();//Open serial port
        byte[] buffer = serialPort.readBytes(10);
        System.out.println(buffer.toString());
        serialPort.closePort();//Close serial port
    }
    catch (SerialPortException ex) {
        System.out.println(ex);
    }
}
}

I got either the port is busy or no output (In the meanwhile I kept on scanning using my barcode scanner)

Answer 1

Here's a solution posted elsewhere on StackOverflow. Basically you need to cycle your available comports from your OS and display/select the intended one. If you're having trouble with this please post some code for us to review.

Answer 2

I'm unfamiliar with those APIs, but fairly familiar with the electrical end of the COM port. There is no automatic "handshake" that indicates whether a device is attached or not, unlike a USB port. However, there are several status lines that are present in the interface.

In addition to the TD/RD signals (transmitted data/received data) there are RTS/CTS -- Request To Send and Clear To Send. RTS and CTS are such that they go "not ready" when nothing is connected.

The usual protocol is that the device asserts RTS and then the other end returns CTS to indicate that everything is ready. However, this is all complicated by the fact that the computer can appear as either a "device" or a "modem" (the only two things that RS-232 knows about). The result is that you can have several different configurations of pins and signals, depending on the assumed modes of the two pieces. (If you're lucky the scanner docs describe some of this.)

Further complicating things is that there are DSR/DTR signals -- Data Set (Modem) Ready and Data Terminal Ready. In most PC configurations these are ignored, but not always.

So, if you don't have luck soon with your scanning you may have to look at the pinouts and use a voltmeter and some jumpers to set you're physical port in a state that the scanner will find. Then there will be further experimentation to determine how to set up the status signals to get the scanner to talk.