Java

private void button_Click(object sender, EventArgs e)
{
  SerialPort sp = new SerialPort(SerialPort.GetPortNames()[0], 9600, Parity.None, 8, StopBits.One);
  String[] str = SerialPort.GetPortNames();
  sp.Open();
  sp.DtrEnable = true;
  sp.RtsEnable = true;
  sp.WriteLine("Hello World!");
  sp.Close();
}

Enumeration pList = CommPortIdentifier.getPortIdentifiers();
CommPortIdentifier cpi = (CommPortIdentifier) pList.nextElement();

if (cpi.getPortType() == CommPortIdentifier.PORT_SERIAL && cpi.getName().compareTo("COM1") == 0) {

  try {
     CommPort port = cpi.open("DarwinSys Printing", 30 * 1000);
      try {
        OutputStream os = port.getOutputStream();
        String str = "Hello World!";
        byte[] b = str.getBytes();
        os.write(b);
        os.flush();
        os.close();
      } catch (IOException ex) {
      }

// i also tried the code below

//   try {
//   serial.setSerialPortParams(9600, SerialPort.DATABITS_8,
//   SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
//   } catch (UnsupportedCommOperationException ex) {
//   }
//    serial.setDTR(true);
//    serial.setRTS(true);
//    serial.notifyAll();
//
//   try {
//     OutputStream os = (OutputStream) serial.getOutputStream();
//     String str = "Hello World!";
//     byte[] b = str.getBytes();
//     os.write(b);
//     os.flush();
//     os.close();
//   } catch (IOException ex) {
//   }
     } catch (PortInUseException ex) {
     }

@Action
    public void button1Pressed() {
        A a = new A();
        a.openConnection();
    }

// this is the method in the class A

public void openConnection() {
    String connectionString = "jdbc:mysql://172.16.11.12:3306/Projector_Manager";
    try {
       Class.forName("com.mysql.jdbc.Driver");
       conn = DriverManager.getConnection(connectionString,"root","1");  // here comes the error
       insertStatement = conn.prepareStatement("insert into Current_Status values (?,?,?,?,?)");
         } catch (SQLException ex) {
         System.out.println(ex.getMessage());
         } catch (ClassNotFoundException ex) {
         System.out.println(ex.getMessage());
         }
    }

Communications link failure<br />
<br />
Last packet sent to the server was 1 ms ago.

public static void main(String[] args)
{
    A a = new A();
    a.openConnection();
}

PrintStream psMyFile = new PrintStream("myFile.txt");

FileOutputStream fos = new FileOutputStream("myFile.txt", true);
PrintStream psErrorStream = new PrintStream(fos);
System.setErr(psErrorStream);

for (int i=0; i<5; i++)
	psMyFile.println("line " + i);

System.err.println("This is an error 1");
psMyFile.println("after the error");
System.err.println("This is an error 2");
psMyFile.println("finished");