How to send sms alerts to mobile using java?

Hi i have used the Code to send message on mobile using java code, it is not working -

COM2 javax.comm.NoSuchPortException at javax.comm.CommPortIdentifier.getPortIdentifier(CommPortIdentifier.java:105)

confusion is there what is COM2 port and how to enable that ? and also what is private String for example csca=" + 9100000000"; // the message center

and also how this code is working?