SQL Server 2008 is not connectable through jdbc intermittently
<p>My Java (1.5) code would try to connect SQL Server 2008 on a scheduled basis (Executor framework) to execute some queries and get data. The problem that I face is sometimes the data is retrieved successfully, and sometimes I get following exception:</p>

<blockquote>
  <p>com.microsoft.sqlserver.jdbc.SQLServerException: The TCP/IP connection to the host , port 1433 has failed. Error: "No route to host. Verify the connection properties, check that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port, and that no firewall is blocking TCP connections to the port.".
      at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDriverError(SQLServerException.java:171)
      at com.microsoft.sqlserver.jdbc.SQLServerConnection.connectHelper(SQLServerConnection.java:1033)
      at com.microsoft.sqlserver.jdbc.SQLServerConnection.login(SQLServerConnection.java:817)
      at com.microsoft.sqlserver.jdbc.SQLServerConnection.connect(SQLServerConnection.java:700)
      at com.microsoft.sqlserver.jdbc.SQLServerDriver.connect(SQLServerDriver.java:842)
      at java.sql.DriverManager.getConnection(DriverManager.java:525)
      at java.sql.DriverManager.getConnection(DriverManager.java:171)</p>
</blockquote>

<p>I made sure that machine is reachable and service is running. Cross verified the firewall as well. </p>

<p>And, the exception does not occur in regular intervals or at any specific time. It's very random. I use com.microsoft.sqlserver.jdbc.SQLServerDriver and sqljdbc.jar.</p>

<p>Connection url is constructed as <code>"jdbc:sqlserver://" + ipAddress + ":" + port</code>, and the connection is created as 
<code>conn = DriverManager.getConnection(this.url, this.username, this.password);</code></p>

<p>Am I making any mistake here? or Is there anything that I need to check/verify?</p>
