SQL JDBC Connection Timed Out, Please Help, I Am In Urgent

Hi there,
i am working on SQL JDBC 2005 version 1.1. I have a liferay portal database located at server 1, wsrp portlets' database located at server 2 (with instance name instance1). The producer (liferay) have to create a connection with server 2 (use connection string) to authenticate the consumer. If the registration properties is valid, then the consumer are able to consume the wsrp portlet. (Note that i use tomcat as web container)

But when the producer connect to server 2, tomcat throws error:
com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host has failed. java.net.ConnectException: Connection timed out: connect
at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.connectHelper(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.loginWithoutFailover(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerConnection.connect(Unknown Source)
at com.microsoft.sqlserver.jdbc.SQLServerDriver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:525)
at java.sql.DriverManager.getConnection(DriverManager.java:193)
at com.mypackage.utils.DBUtils.getDBConnection(DBUtils.java:45)

My connection string pattern is : "jdbcqlserver://{0}:{1};User={2};Password={3};DatabaseName={4}"
Which {0}: server name

{1}: port,
......
for ex: jdbcqlserver://server2instance1,2345:2345;User=sa;Password=Sa;DatabaseName=mydb

Is my string correct ?

Note that the error occur intermittent, not everytime.

If any one there who have got or experienced with this error, please help me. Thanks you very much