Java – Exception while connecting to DB2 in java using JDBC

I am trying to connect to a db2 database in Java. Below the driver and the connection string and the driver details i am giving

Class.forName("COM.ibm.db2.jdbc.net.DB2Driver");
String url="jdbc:db2://hostname:portnumber/databasename";
sourceConnection=DriverManager.getConnection(url,"username","password");

But I am getting the below exception

"COM.ibm.db2.jdbc.DB2Exception: [IBM][JDBC Driver] CLI0615E  Error receiving from socket, server is not responding. SQLSTATE=08S01"

I also tried changing the connection string to
String url="jdbc:db2:hostname:portnumber/databasename";

Still it is resulting the same exception above while trying to get the Connection.

And i have tried the below option also using JDBC app driver

Class.forName("COM.ibm.db2.jdbc.app.DB2Driver");     
DB2DataSource db2ds = new DB2DataSource();
db2ds.setServerName("hostname");
db2ds.setPortNumber(portnumber);
db2ds.setDatabaseName("databasename");
db2ds.setUser("username");
db2ds.setPassword("password");
sourceConnection=db2ds.getConnection();

For the above two connection I used the jar "db2java.jar"

And i have tried using the JCC driver:

Class.forName("com.ibm.db2.jcc.DB2Driver");
String url="jdbc:db2://hostname:portnumber/databasename";
sourceConnection=DriverManager.getConnection(url,"username","password");

For this connection i have added the below jars
1)db2jcc.jar
2)db2jcc_license_cu.jar

This time around I am getting the below error,

"com.ibm.db2.jcc.am.go: [jcc][t4][201][11237][3.57.82] Connection authorization failure occurred.  
Reason: Security mechanism not supported. ERRORCODE=-4214, SQLSTATE=28000"

I tried to connect to the same db2 source using "Quest for DB2" tool and the connection was successful.

Am i missing something in the code and is it a problem with DB2 drivers or connection string?

Can someone please guide me.

Thanks in advance.